Observations of SN 2005cf

A Golden Standard Type Ia Supernova SN 2005cf: Observations from the Ultraviolet to the Near-Infrared Wavebands

Abstract

We present extensive photometry at ultraviolet (UV), optical, and near-infrared (NIR) wavelengths, as well as dense sampling of optical spectra, for the normal type Ia supernova (SN Ia) 2005cf. The optical photometry, performed at eight different telescopes, shows a scatter of 0.03 mag after proper corrections for the instrument responses. From the well-sampled light curves, we find that SN 2005cf reached a -band maximum at mag, with an observed luminosity decline rate mag. The correlations between the decline rate and various color indexes, recalibrated on the basis of an expanded SN Ia sample, yield a consistent estimate for the host-galaxy reddening of SN 2005cf, e.g., mag. The UV photometry was obtained with the Hubble Space Telescope and the Swift Ultraviolet/Optical Telescope, and the results match each other to within 0.1–0.2 mag. The UV light curves show similar evolution to the broadband , with an exception in the 2000–2500 Å spectral range (corresponding to the F220W/uvm2 filters), where the light curve appears broader and much fainter than that on either side (likely owing to the intrinsic spectral evolution). Combining the UV data with the ground-based optical and NIR data, we establish the generic UV-optical-NIR bolometric light curve for SN 2005cf and derive the bolometric corrections in the absence of UV and/or NIR data. The overall spectral evolution of SN 2005cf is similar to that of a normal SN Ia, but with variety in the strength and profile of the main feature lines. The spectra at early times displayed strong, high-velocity (HV) features in the Ca II H&K doublet and NIR triplet, which were distinctly detached from the photosphere ( km s) at a velocity ranging from 19,000 to 24,000 km s. One interesting feature is the flat-bottomed absorption observed near 6000 Å in the earliest spectrum, which rapidly evolved into a triangular shape and then became a normal Si II 6355 absorption profile at about one week before maximum brightness. This pre-maximum spectral evolution is perhaps due to the blending of the Si II 6355 at photospheric velocity and another HV absorption component (e..g., Si II shell at a velocity 18,000 km s) in the outer ejecta, and may be common in other normal SNe Ia. The possible origin of the HV absorption features is briefly discussed.

Subject headings:
supernovae: general – supernovae: individual (SN 2005cf)
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1. Introduction

Type Ia supernovae (SNe Ia) play important roles in diverse areas of astrophysics, from chemical evolution of galaxies to observational cosmology. They, together with the core-collapse SNe, are responsible for most of the heavy elements in the universe. SNe Ia have also been used over the past decade as the most powerful tool probing the expansion history of the universe. Owing to a relatively homogeneous origin — probably an accreting carbon-oxygen white dwarf (WD) with a mass close to the Chandrasekhar limit (1.4 M) in a binary system (for a review see Hillebrandt & Niemeyer 2000) — most SNe Ia show strikingly similar spectral and photometric behavior (e.g., Branch & Tammann 1992; Suntzeff 1996; Filippenko 1997). In particular, the observed peak luminosities of SNe Ia have been shown to correlate with the shapes of their light or color curves (e.g., Phillips 1993; Hamuy et al. 1996; Riess et al. 1996; Perlmutter et al. 1997; Wang et al. 2003; Wang et al. 2005; Guy et al. 2005; Prieto et al. 2006; Jha et al. 2007; Guy et al. 2007; Colney et al. 2008), leading to an uncertainty of 10% in distance measurements from SN Ia.

Based on the observations of SNe Ia at redshifts , Riess et al. (1998) and Perlmutter et al. (1999) first reported the discovery of an accelerating universe. The evidence for the acceleration expansion from SNe Ia improved markedly with follow-up studies (Barris et al. 2004; Tonry et al. 2003; Knop et al. 2003; Riess et al. 2004, 2007; Astier et al. 2006; Wood-Vasey et al. 2007a), suggesting that 70% of the universe is composed of a mysterious dark energy (for a review see, e.g., Filippenko 2005a). Elucidating the nature of dark energy would require a large sample of well-observed SNe Ia at even higher redshifts (e.g., ), and also relies on the improvement of the SN Ia standardization (e.g., 0.01 mag). Progress can be made by searching for additional luminosity-dependent parameters, or by identifying a subsample of SNe Ia with the lowest scatter of the luminosity. This depends on the degree of our understanding of SN Ia physics as well as on the good controlling of various systematic effects such as the photometry itself, the SN luminosity evolution, and the absorption by dust. Clarification of the above issues demands a large sample of SNe Ia with well-observed spectra and light curves, from which we can get better constraints of their physical properties.

Quite a few detailed studies have been conducted of spectroscopically and/or photometrically peculiar SNe Ia such as SNe 1991T (Filippenko et al. 1992a; Phillips et al. 1992), 1991bg (Filippenko et al. 1992b, Leibundgut et al. 1993), 2000cx (Li et al. 2001; Thomas et al. 2003; Candia et al. 2003), 2002cx (Li et al. 2003; Branch et al. 2004; Jha et al. 2006a), and 2006gz (Hicken et al. 2007). A comparable number of relatively normal SNe Ia have also been individually studied, including SNe 1994D (Patat et al. 1996), 1996X (Salvo et al. 2001), 1998aq (Branch et al. 2003; Riess et al. 2005), 1998bu (Jha et al. 1999), 1999ee (Stritzinger et al. 2002; Hamuy et al. 2002), 2001el (Krisciunas et al. 2003), 2002er (Pignata et al. 2004), 2003cg (Elisa-Rosa et al. 2006), 2003du (Stanishev et al. 2007), 2004eo (Pastorello et al. 2007a), 2002bo (Benetti et al. 2004), and 2006X (Wang et al. 2008a), though the last two may differ from other typical SNe Ia due to an unusually high expansion velocity of their photospheres and a relatively flat evolution of their -band light curves starting from the early nebular phase (Wang et al. 2008a). However, a much larger sample of SNe Ia must be investigated in order to determine the dispersion among their properties and refine possible systematic effects for precision cosmology. In addition, the sample of “golden standard” SNe Ia having extensive observations from ultraviolet (UV) through near-infrared (NIR) wavelengths is sparse. The UV properties could provide clues to the diversity and evolution of the progenitor system, as they are more sensitive to the metallicity of the ejecta as well as the degree of mixing of the synthesized Ni (Höflich et al. 1998; Blinnikov & Sorokina 2000), while the NIR data are particularly suitable for the study of dust properties and the determination of absorption corrections. The UV and NIR data are also important in helping to determine, by means of the light curves, the bolometric luminosity of SNe Ia.

In this paper, we present extensive observations of the SN Ia 2005cf in UV, optical, and NIR bands, providing a “golden standard” with which to compare other SNe Ia. Pastorello et al. (2007b; hereafter P07) and Garavini et al. (2007; hereafter G07) have previously studied the optical properties of SN 2005cf, but our unique UV data along with an excellent independent optical/NIR dataset allow us to provide better constraints on the properties of SN 2005cf. We compare our results with those of P07 and G07 where appropriate. Our observations and data reduction are described in §2, while §3 presents the UV-optical-NIR () light curves, the color curves, and the reddening estimate. The spectral evolution is given in §4. In §5 we construct the bolometric light curve of SN 2005cf. Our discussion and conclusions are given in §6.

2. Observations and Data Reduction

SN 2005cf was discovered at an unfiltered magnitude of 16.4 on 2005 May 28.36 (UT dates are used throughout this paper) by Pugh & Li (2005) during the Lick Observatory Supernova Search (LOSS) with the 0.76 m Katzman Automatic Imaging Telescope (KAIT; Filippenko et al. 2001; Filippenko 2005b), with J2000 coordinates = 152132.21 and = . It exploded in the vicinity of the tidal bridge connecting the S0 galaxy MCG01-39-003 with the nearby Sb galaxy MCG01-39-002 (NGC 5917); see Figure 1. Assuming MCG01-39-003 is the host galaxy of SN 2005cf, we find that the supernova was west and north of the galaxy nucleus.

An optical spectrum taken on 2006 May 31.22 revealed that SN 2005cf was a very young SN Ia, at a phase of 10 d before maximum brightness (Modjaz et al. 2005). On this basis, we requested frequent optical and NIR imaging, as well as optical spectroscopy; we collected a total of 634 photometric datapoints and 39 optical spectra. Moreover, Hubble Space Telescope (HST) UV and NIR observations were soon triggered (proposal GO-10182; PI A. V. Filippenko) with the Advanced Camera for Surveys (ACS) and the Near-Infrared Camera and Multi-Object Spectrometer (NICMOS) at 12 different epochs. UV and optical photometry was also obtained with the Ultraviolet/Optical Telescope (UVOT) on the space-based Swift telescope.

Figure 1.— SN 2005cf in MCG01-39-003. This is a -band image taken with the 0.8 m TNT on 2005 Sep. 21. The supernova and 16 local reference stars are marked. North is up, and east is to the left.

2.1. Ground-Based Observations

Optical and NIR Photometry

The ground-based optical photometry of SN 2005cf, spanning from 12 d before to 3 months after the -band maximum, was obtained with the following telescopes: (1) the KAIT and the 1.0 m Nickel telescope at Lick Observatory in California; (2) the 1.2 m telescope at the Fred Lawrence Whipple Observatory (FLWO) of the Harvard-Smithsonian Center for Astrophysics (CfA) in Arizona; (3) the 1.3 m and 0.9 m telescopes at Cerro Tololo Inter-American Observatory (CTIO) in Chile; (4) the 1.5 m telescope at Palomar Observatory in California (Cenko et al. 2006); (5) the 2.0 m Liverpool telescope at La Palma in Spain; and (6) the 0.8 m THCA-NAOC Telescope (TNT) at Beijing Xinglong Observatory (BAO) in China. Broad-band photometry was obtained with all the above telescopes, except for the FLWO 1.2 m and Liverpool 2.0 m telescopes which followed SN 2005cf in and Sloan filters. Observations made with KAIT, FLWO 1.2 m, the CTIO 0.9 m, and the Nickel 1.0 m also sampled the band. Table 1 lists the average color terms for all of the involved telescopes and filters. The NIR () photometry was obtained with the 1.3 m Peters Automated Infrared Imaging Telescope (PAIRITEL; Bloom et al. 2006) at FLWO.

As part of routine processing, all CCD images were corrected for bias, flat fielded, and cleaned of cosmic rays. Since SN 2005cf is isolated far away from the host-galaxy center, we omitted the usual step of subtracting the galaxy template from the SN images; instead, the foreground sky was determined locally and subtracted. Instrumental magnitudes of the SN and the local standard stars (labeled in Fig. 1) were measured by the point-spread function (PSF) fitting method, performed using the IRAF43 DAOPHOT package (Stetson 1987).

The transformation from the instrumental magnitudes to the standard Johnson (Johnson 1966) and Kron-Cousins (Cousins 1981) systems was established by observing, during a photometric night, a series of Landolt (1992) standards covering a large range of airmasses and colors. The average value of the photometric zeropoints determined on 7 photometric nights was used to calibrate the local standard stars in the field of SN 2005cf. Table 2 lists the standard magnitudes and uncertainties of 16 comparison stars which were used to convert the instrumental magnitudes of the supernova to those of the standard system. Note, however, that our -band calibration may have an uncertainty larger than that quoted in Table 2, as it was established on only a single photometric night. The calibrations of SN 2005cf were also used by Li et al. (2006) to calibrate the Swift UVOT optical observations.

A comparison of 9 standard stars in common with P07 reveals that some systematic differences exist between the datasets. With respect to P07, our measurements are fainter by mag in , mag in , mag in , mag in , and mag in . The discrepancies are non-negligible and worrisome, especially in the band. Such differences were also noticed by Stanishev et al. (2007) in studying photometry of the comparison stars of SN 2003du; their measurements of the stars in common were found to be systematically brighter than those given in Leonard et al. (2005) and Anupama et al.(2005) by 0.04-0.06 mag in some wavebands. The origin is unclear, and further studies are needed if systematic errors are to be minimized (to mag) when using SNe Ia to measure cosmological distances.

To reasonably assemble the optical photometric data for SN 2005cf obtained with different telescopes and place them on the Johnson-Cousins system [e.g., from the Sloan to the broad-band ], we applied additional magnitude corrections (-corrections; Stritzinger et al. 2002) to the photometry. This is because the color-term corrections only account for the differences derived from normal stars, whereas the spectra of SNe are quite dissimilar. Properly modeling the instrumental response is essential for deriving reliable -corrections. The normalized instrumental response functions, obtained by multiplying the filter transmission functions with the quantum efficiency of the CCD detectors and the atmospheric transmission, are shown in Figure 2. Details of the application of the -corrections are given in the Appendix.

Figure 2.— Comparison of instrumental responses of the seven telescopes, normalized to the peak transmission, with the standard Bessell Johnson/Kron-Cousins functions.

Figure 3 shows the time evolution of the -corrections and the resulting color variances for different telescopes, computed with the spectra of SN 2005cf presented in this paper and those published by G07, as well as with some late-time spectra of SN 2003du (Stanishev et al. 2007). Note that all of the -band filter responses were cut off at 3300 Å in the convolution due to the spectral coverage. The resulting -corrections are generally small in bands, but can be noticeably large in the and bands (e.g., 0.1–0.2 mag). It is worth noting that, without applying such a systematic magnitude correction, the color measured at the CTIO 0.9 m and Palomar 1.5 m (or Lick 1.0 m) telescopes could differ by 0.1 mag in the early nebular phase when the colors are usually used as the reddening indicators.

Figure 3.— Time evolution of the -corrections at the various telescopes.

Applying the -corrections to the photometry noticeably improved the consistency of the datasets obtained with different telescopes. This is demonstrated in Fig. 4, where the scatter around the best-fit curve decreases from 0.06 mag to 0.03 mag in the band. Improvements are also achieved for the other bands, with the photometric scatter reduced to within 0.02–0.03 mag. Such a normalization in the photometry could be potentially important when comparing the properties of SNe measured with different systems. This is because a shift of a few percent in the color might systematically bias the extinction correction, hence producing an error of 10% (a factor of 3–4 larger) in the derived luminosity of the SN.

We further applied -corrections to our photometry using the same set of spectra as for the -corrections. We note that the -band -correction could reach 0.06 mag at the earliest phases, perhaps due to a rapid evolution of the spectral shape. The large - and -corrections required in the band, which were usually unavailable due to the insufficient spectral coverage, might partially account for the large scatter seen in the -band light curve of SN 2005cf.

The final calibrated magnitudes, after performing the - and -corrections, are presented in Table 3. The error bars (in parentheses) are dominated by the uncertainty in the calibration of the comparison stars.

Since the NIR observations of SN 2005cf were conducted with PAIRITEL, the instrument that defines the 2MASS photometric system, we use the 2MASS point-source catalog (Cutri et al. 2003) to calibrate the supernova. The calibrated magnitudes of SN 2005cf are given in Table 4, which were corrected for the -corrections (Columns (7)-(9)) computed from the NIR spectra of SN 1999ee. No -corrections were applied to the NIR photometry because of the similarity of the transmission curves between the 2MASS system and the Persson et al. (1998) system. The filter transmission curves of these two systems are shown in Figure 5.

Figure 4.— The -band light curve of SN 2005cf with and without applying the -corrections. The solid line in the upper panel represents the best fit to the -corrected light curve.

Optical spectroscopy

Low-resolution spectra of SN 2005cf were obtained with the Kast double spectrograph (Miller & Stone 1993) on the 3.0 m Shane telescope at Lick Observatory and the FAST spectrograph (Fabricant et al. 1998) on the Tillinghast 1.5 m telescope at FLWO. Two late-time spectra were also obtained at the W. M. Keck Observatory: one with the Low Resolution Imaging Spectrometer (LRIS; Oke et al. 1995) mounted on the 10 m Keck I telescope, and the other with the Deep Extragalactic Imaging Multi-Object Spectrograph (DEIMOS; Faber et al. 2003) mounted on the 10 m Keck II telescope. A journal of the spectroscopic observations is given in Table 5.

All spectra were reduced using standard IRAF routines (e.g., Foley et al. 2003). For the Lick/Kast observations, flatfields for the red-side spectra were taken at the position of the object to reduce NIR fringing effects. For two Lick/Kast spectra taken on 2005 June 10 and June 11, there was condensation on the red-side camera, producing non-standard and variable absorption features. To compensate for this effect, we created a two-dimensional surface map of a flat field image. We smoothed the surface map to remove any fringing in the flat. We then divided our images by this surface to remove the absorption features from our images. Although this process produced significantly improved spectra, there are still some persistent systematic features in those spectra. The Keck/DEIMOS data were reduced using a modified version of the DEEP pipeline and our own routines as described by Foley et al (2007).

Flux calibration of the spectra was performed by means of spectrophotometric standard stars observed at similar airmass on the same night as the SN. Using our own IDL routines, the extracted, wavelength calibrated spectra were corrected for continuum atmospheric extinction using mean extinction curves for FLWO and Lick Observatory; moreover, telluric lines were removed from the data. For all the spectra observed at Lick and FLWO, the slit was always aligned along the parallactic angle to avoid chromatic effects in the data (Filippenko 1982).

2.2. HST UV and NIR Observations

ACS UV Photometry

Imaging of SN 2005cf was carried out with the HST ACS High Resolution Camera (HRC) during Cycle 13. The field of view of this CCD-based instrument is about with a scale of pixel. The observations were made in the F220W, F250W, and F330W bands, with exposure times of 1040 s, 800 s, and 360 s, respectively. The exposure time was split into several equal segments that were used in the data reduction process to reject cosmic-ray events. The data produced by the STScI reduction pipeline had bias and dark-current frames subtracted and were divided by a flatfield image. In addition, known hot pixels and other defects were masked. Individual exposures were combined using the MultiDrizzle task within STSDAS to reject cosmic rays and perform geometric-distortion corrections.

To get the optimal signal-to-noise ratio (S/N), we performed aperture photometry in all of the drizzled images using an aperture radius of 4 pixels (). The background level was determined from the median counts in an annulus of radius 100–130 pixels. The measured magnitudes were further corrected to an infinite-radius aperture and placed on the Vega magnitude system (Sirianni et al. 2005). The final HST ACS UV magnitudes of SN 2005cf are listed in Table 6. Uncertainties were calculated by combining in quadrature the Poisson photon errors, the readout-noise errors from the pixels within the aperture, and errors in the aperture correction.

Figure 5.— Comparison of near-infrared transmission curves of PAIRITEL (ex-2MASS) and HST NICMOS3 with that of the Persson et al. (1998) system.

NICMOS NIR Photometry

The infrared observations were obtained with the HST NICMOS3, which has a scale of pixel and a field of view of . Images were acquired through the F110W and F160W filters (see Fig. 5 for the transmission curves) at similar epochs as the optical ones with the ACS. The data were preprocessed using the STSDAS package CALNICA and the latest reference files provided by STScI. Unlike the ACS, the NICMOS calibrated data are given in count rate (DN s, where DN are data-number counts).

Aperture photometry was performed on the calibrated NICMOS3 images. Counts were summed within an aperture of 5.5 pixel radius (, the size of the aperture used for the standard-star measurements) centered on the source. To correct for a nominal infinite aperture, the measured count rates in F110W and F160W were, respectively, multiplied by 1.056 and 1.087. The total count rates were then converted into flux using the recently determined photometric scale factors, Jy s DN at 1.1 m and Jy s DN at 1.6 m. Corresponding zeropoints were calculated on the Vega system, assuming the zero-magnitude flux densities of 1886 and 1086 Jy and the effective wavelengths of 1.12 m and 1.60 m for F110W and F160W, respectively. All of the above parameters involved in the calculations were taken from the website for HST NICMOS photometry44.

As the NICMOS3 filters do not match ground-based well (especially the F110W filter, which is much broader and bluer), it is necessary to apply -corrections as well as color-term corrections to place the photometry on the ground-based system. A total of six stars (2 white dwarfs, 2 solar analogs, and 2 red stars) have been observed through both the NICMOS NIR system (F110W, F160W, and F222M filters) and the ground-based system (Persson et al. 1998). These stars, along with the Sun, Vega, and Sirius with model IR spectra from the Kurucz web site45, allow us to establish a rough transformation between the NICMOS3 and the ground-based NIR systems for normal stars. In computing the NIR -corrections we used data for SN 1999ee (Hamuy et al. 2002), which has relatively good temporal coverage of the NIR spectra and a value of similar to that of SN 2005cf.

Table 7 gives the color-, - and -corrected NIR photometric results from the HST NICMOS3 images, consistent with the ground-based measurements within the error bars. The - and color-corrections that were added to normalize the photometry to the Persson et al. (1998) system are also listed.

2.3. Swift UVOT Optical/UV Observations

SN 2005cf was also observed with the Ultraviolet/Optical Telescope (UVOT; Roming et al. 2005) onboard the Swift observatory (Gehrels et al. 2004), covering from 8 d before to 42 d after the -band maximum. The photometric observations were performed in three UV filters (uvw1, uvm2, and uvw2) and three broadband optical filters (, , and ). As shown in Figure 6, the instrumental response curves of the UVOT uvm2 and uvw1 filters are, respectively, very similar to those of the HST ACS F220W and F250W filters. The UVOT optical filters are close to the standard Johnson system in and but exhibit noticeable difference in .

Figure 6.— Comparison of transmission curves of Swift UVOT filters with HST ACS in the UV and with the Johnson system in .

Images of SN 2005cf were retrieved from the Swift Data Center, and were reprocessed utilizing an improved plate scale for the uvw2 images and corrections to the exposure times in the image headers (Brown et al. 2008). To maximize the S/N, we performed aperture photometry using an optimal aperture of radius suggested by Li et al. (2006), after first subtracting the host-galaxy light using a template image. Since the UVOT is a photon-counting detector and suffers from coincidence losses when observing bright sources, the observed counts of SN 2005cf were corrected for such losses using the empirical relation described by Poole et al. (2008). Finally, aperture corrections were applied to bring the measurements from an aperture of to the aperture with which the photometric zeropoints are calibrated on the Vega magnitude system.

As the instrumental response curves of the UVOT optical filters do not follow exactly those of the Johnson system (see also Fig. 6), some color terms are expected. We calculated the synthetic color terms by convolving the instrumental response of the UVOT in the optical with the 93 spectrophotometric Landolt standard stars published by Stritzinger et al. (2005). These are 0.104, 0.012, and 0.030 in a linear correlation of the parameter pairs (, ), (, ), and (, ), respectively.

The synthetic color terms are small in the and bands but relatively large in the band. Our determinations are consistent with those measured by Poole et al. (2008) who preferred a polynomial expression. The -corrections of the UVOT optical filters were derived using spectra of SN 2005cf; they are given in Table 8 (columns 10–12) and are non-negligible in the band (e.g., 0.1–0.2 mag). Columns 4–9 in Table 8 list the final UVOT UV/optical magnitudes. The magnitudes in optical have been corrected for the color- and -corrections.

3. Light Curves of SN 2005cf

Figure 7 shows the light curves of SN 2005cf. The - and -corrections have been applied to the light curves in all of the optical and NIR bands. No S- or K-corrections were applied to the UV data. The optical light curves were sampled nearly daily during the period to +90 d, making SN 2005cf one of the best-observed SNe Ia. The morphology of the light curves resembles that of a normal SN Ia, having a shoulder in the band and pronounced secondary-maximum features in the NIR bands. The NIR light curves of SN 2005cf reached their peaks slightly earlier than the -band curve. This is also the case for the UV light curves, which are found to have narrower peaks, with the exceptions of the HST ACS F220W and the Swift UVOT uvm2 filters. Detailed analysis of the light curves is described in the following subsections.

Figure 7.— The UV, optical, and NIR light curves of SN 2005cf. The UV light curves were obtained from the photometry with HST ACS and the Swift UVOT; the optical photometry was collected at eight ground-based telescopes as well as the Swift UVOT; and the data were taken with the 1.3 m PAIRITEL and with HST NICMOS3.

3.1. Optical Light Curves

A polynomial fit to the -band light curve around maximum brightness yields mag on JD 2,453,533.66 0.28 (2005 June 12.16). The maximum epoch is consistent with the estimate by P07 while itself is fainter than that of P07 by 0.09 mag. The derived value of indicates that our observations started from 11.9 d and extended to +90.3 d with respect to the maximum. Likewise, the -band light curve reached a peak magnitude of on JD 2,453,535.54 0.33, about 1.9 d after . A comparable measurement was obtained by P07 who gives mag. The fitting parameters for the maxima in the other bands are presented in Table 9, together with the initial decline rates within the first 15 d after their maxima (see below).

From the - and -band light curves, we derive an observed mag and mag.46 These values are slightly smaller and redder than those given by P07 [ and ]. We also measured the color at 12 d after the maximum (Wang et al. 2005), obtaining mag. After removal of the Galactic reddening, these color indexes are slightly redder than the intrinsic value (see also descriptions in §3.3), suggesting some line-of-sight reddening toward SN 2005cf.

Based on the extremely well-sampled photometry in the optical, we constructed the light-curve templates of SN 2005cf by using a smoothing spline function. To obtain better sampling in the band, the late-phase data from P07 were also included in the fit. We tabulate the template light curves in Table 11. In Figure 8, we compare the best-fit light-curve templates of SN 2005cf with observations from the Swift UVOT and P07. We also compare them with other well-observed, nearby SNe Ia having similar values, including SNe 2001el ( mag; Krisciunas et al. 2003), 2002bo ( mag; Benetti et al. 2004; Krisciunas et al. 2004), 2002dj ( mag; Pignata et al. 2008), 2003du ( mag; Stanishev et al. 2007), and 2004S ( mag; Krisciunas et al. 2007; Chornock & Filippenko 2008). These 6 objects include all SNe Ia with and at least 15 epochs per band of published data. The data for SNe 2002bo, 2002dj, and 2004S obtained with KAIT (Ganeshalingam et al., in prep.) are overplotted. The photometric data for the above comparison SNe Ia were -corrected. To be consistent with SN 2005cf, the -corrections computed with the spectra of the comparison SNe and/or the spectra of SN 2005cf were also applied to their photometry. All of the light curves of the comparison SNe Ia have been normalized to the epoch of their maxima and shifted in their peaks to match the templates of SN 2005cf.

Figure 8.— Comparison of light curves of SN 2005cf with those published by Pastorello et al. (2007) and other well-observed SNe Ia: SNe 2001el, 2002bo, 2002dj, 2003du, and 2004S. See text for the references.

The overall comparison with the photometry of P07 reveals some systematic differences, especially at the earlier phases, as shown in Figure 9. The magnitudes in P07 are found to be brighter than ours on average over time by mag in , mag in , mag in , and mag in , while they are fainter by mag in (see the filled circles in Fig. 9). This is primarily due to calibration differences, especially in the bands. It is puzzling, however, that a remarkable difference of 0.14 mag in the band for the comparison stars (see §2.1.1) is not also seen in the -band SN photometry. Additional, uncorrected systematic effects are probably present.

With the constructed light-curve templates of SN 2005cf, one may also examine whether the Swift UVOT optical observations are consistent with the ground-based data. The mean values of the computed residuals between these two measurements (see the star symbols in Fig. 9) are mag in , mag in , and mag in . There appears to be a small systematic shift in , but the consistency in the and bands is satisfactory. This demonstrates the great improvements recently achieved in Swift UVOT calibrations (Li et al. 2006; Poole et al. 2008).

Although the light curves of the comparison SNe Ia are similar to each other near maximum brightness, they diverge at earlier (rising) phases. SNe 2001el and 2003du displayed a slower rise rate in each of the bands. In contrast, the brightness of SNe 2002bo and 2002dj rose at a faster pace than that of SN 2005cf (see also Pignata et al. 2008). This indicates that the rise time might slightly vary among SNe Ia having similar values, though a larger sample having early-epoch observations is needed to verify this trend.

Differences in the light curves also emerge at late phases, especially in the band. We measured a late-time decline rate mag (100 d) in for SN 2005cf during the interval –90 d, which is comparable to that of SNe 2001el, 2003du, and 2004S at similar phase. While SNe 2002bo and 2002dj showed much slower decay rates, e.g., mag (100 d), and they happened to be events with high expansion velocity of the photosphere. These fast-expanding SNe may generally have flatter photometric evolution in at late times, similar to that of SN 2006X (Wang et al. 2008a).47

Figure 9.— The residual magnitudes of the comparison SNe Ia with respect to the light-curve templates derived from our observations of SN 2005cf.

In contrast to the - and -band evolution, the light curves in the and bands appear more heterogeneous. The largest dispersion is in the premaximum -band evolution and in the -band secondary-maximum phase. Systematic effects due to filter mismatches might not be fully removed by the -corrections because of the incomplete wavelength and/or temporal coverage for the SN spectra. Nevertheless, part of the dispersion is likely to be intrinsic. Significant spectral variations at the wavelengths of the broad-band were also found in SNe Ia at redshift z0.5 (Ellis et al. 2008). The -band brightness has also been proposed to depend sensitively on the metallicity of the progenitor (e.g., Höflich et al. 1998; Lentz et al. 2000; Sauer et al. 2008), which may vary from one supernova to another; while emission in the band is heavily affected by the Ca II NIR triplet absorption, which is found to vary substantially among SNe Ia at early phases (see Fig. 17 in §4.1).

3.2. The UV Light Curves

UV observations are important for understanding SN Ia physics as well as possible differences among the progenitors in a range of environments. Due to the requirement of space-based observations, however, UV data for SNe Ia have been sparse; see Panagia (2003) and Foley, Filippenko, & Jha (2008) for summaries of International Ultraviolet Explorer (IUE) and HST spectra. In HST Cycle 13, extensive UV observations of SNe Ia were conducted (program GO-10182; PI Filippenko); unfortunately, the Space Telescope Imaging Spectrometer (STIS) failed just before the program began, so the UV prism in ACS was used instead, yielding spectra far inferior to those anticipated with STIS. Recently, Swift has obtained UV photometry of SNe Ia (Brown et al. 2008; Milne et al. 2008, in prep.), as well as some low-quality UV ugrism spectra (Bufano et al., in prep.).

Figure 10 shows the UV light curves of SN 2005cf obtained with the Swift UVOT and the uvw1, uvw2, and uvm2 filters, as well as with the HST ACS and the F220W, F250W, and F330W filters. These two UV data sets span the periods from  d to  d and from  d to  d, respectively. Overlaid are the -band templates of SN 2005cf, shifted to match the peak of the UV bands. With respect to , the F330W-band light curve has a noticeably narrower peak. The UVOT light curve closely resembles that in the HST F250W band, with the former being slightly brighter by mag. Despite the similarity of the filter responses, the UVOT light curve appears to be systematically dimmer than that of HST F220W by 0.2 mag at comparable phases. This is perhaps due to the calibration uncertainty or reduction errors, but more data are obviously needed to clarify this difference.

Figure 10.— UV light curves of SN 2005cf, obtained with the HST ACS (F220W, F250W, and F330W) and the Swift UVOT (, , ). The first two and the last two data points in the band are 3- upper limits of the detection. Overlaid are the -band template of SN 2005cf (dashed line).

The temporal behavior of the UV photometry of SN 2005cf is similar to the optical behavior, but with different epochs for the maximum brightness. As in the band, most of the UV light curves reached their maximum slightly before the optical, with the exception of the uvm2/F220W-band photometry, which peaks 3–4 d after the maximum. Another interesting feature is that the light-curve peak in these two filters appears to be much fainter and broader than that of the other UV filters on both sides. A similar feature was seen in SN 2005am (Brown et al. 2005), a normal SN Ia resembling SN 1992A (Kirshner et al. 1993). Brown et al. (2005) suggested that the faintness in could be explained in terms of a bump of the extinction curve near 2200 Å (Cardelli et al. 1989). Assuming a total reddening of mag (see §3.6), however, we find that the change of could only result in a larger extinction in /F220W by 0.5 mag. This is far below the flux drop of 1.5 mag with respect to the neighboring bands, as seen in SN 2005cf. The red leak in the UV filters might cause the abnormal behavior in the UV light curves by including some optical light, due to the red tail. However, the report from the most recent check of the HST ACS CCDs shows that such an effect is small in the UV filters 48. Moreover, the off-band contamination in the F220W filter is found to be larger than that in F250W. This shows that the UV leak may not be responsible for the faint brightness in F220W or uvm2 filters.

As in the optical, the light-curve parameters in the UV were obtained by using a polynomial fit to the observations (see Table 9). One can see that the luminosity in the F330W band is the brightest, but it declines at the fastest pace after the initial peak. The -band luminosity is the faintest, and has a post-maximum decay rate much slower than the other UV filters.

3.3. The NIR Light Curves

The NIR photometry of SN 2005cf was obtained with PAIRITEL (Wood-Vasey et al. 2007b) and the HST NICMOS3, spanning from  d to +29.1 d with respect to . Due to significant differences between these two photometric systems, we applied both color- and -corrections to the HST photometry to normalize it to the PAIRITEL system. As shown in Figure 11, the corrected F110W- and F160W-band magnitudes (smaller filled circles) are consistent with the ground-based results.

Figure 11.— Comparison of the NIR light curves of SN 2005cf with those of SNe 2001el, 2002bo, 2002dj, 2003du, and 2004S. All light curves are shifted in time and magnitude to fit the peak values of SN 2005cf. The data sources are cited in the text.

In Figure 11, the NIR data of the comparison SNe Ia are overlaid. Although the light curves of all these SNe are similar near maximum, they diverge after the peak phase. As in the optical, SNe 2002dj and 2002bo rise at a faster pace than SNe 2005cf and 2003du in the NIR. Scatter is also present near the secondary-maximum phase; the fast-expanding events tend to exhibit more prominent peaks. The secondary-peak feature in the band appears somewhat less pronounced in SN 2001el.

The peak magnitudes in the NIR, estimated by fitting the data with the Krisciunas et al. (2004a) templates, are reported in Table 9. In contrast with the rapid decline in after the primary maximum, the - and -band light curves show much slower decay at comparable phases.

3.4. The Spectral Energy Distribution Evolution

The evolution of the spectral energy distribution (SED) can be best studied through spectroscopy; however, only the optical spectra of SN 2005cf were involved in our study. As an alternative, a rough SED can be constructed from the observed fluxes in various passbands at the same or similar epochs. Since we have photometry in the UV, optical, and NIR bands, covering the 1600–24,000 Å region, we can study the SED evolution of SN 2005cf by means of photometry. Because of the numerous instruments involved in the observations of SN 2005cf, it was not always possible to observe all bands at exactly the same time, and our definition of the “same epoch” refers to a reference date 1 d. The observed apparent magnitudes in each passband were converted to fluxes using the reddening derived in §3.6.

Figure 12.— The spectral energy distribution evolution of SN 2005cf at , , +5, +18, and +42 d after the -band maximum. The photometric points are shown with error bars (vertical ones for uncertainties and horizontal ones for the FWHM of the filters). Overlayed are the HST FOS spectra of SN 1992A (dotted curves) from Kirshner et al. (1993), obtained at  d and +45 d, respectively. Note that the error bar of the flux is in most cases smaller than the size of the symbol.

Figure 12 shows SEDs at five selected epochs, , , +5, +17, and +42 d after the -band maximum. The SN 2005cf SED went through dramatic changes in going from epochs near maximum to the nebular phase. The SEDs at , and +5 d are very similar, peaking in but showing a flux deficit in F220W/uvm2 (2000–2500 Å). At these early phases, the emission from the supernova dominated in the blue. By  d the SED showed a significant deficit at short wavelengths compared with earlier epochs, whereas the NIR remained fairly constant (with the exception of the band). The flux peak shifted to the band by  d, and the deficit in F220W/uvm2 might become less noticeable, though the measurement from the UVOT is around the detection limit.

To better understand the evolution of the 2000–2500 Å region, we overplot the HST FOS spectra of SN 1992A (Kirshner et al. 1993) in Figure 12. One sees that the F220W/uvm2-band flux deficit in SN 2005cf at  d is consistent with the strong absorption trough present in the UV spectrum of SN 1992A at similar epochs, although the UV brightness of the latter seems relatively fainter with respect to their optical emission. This absorption feature could arise from multiplets of the iron-peak elements at ejection velocities above 16,000 km s, such as Fe II 2346, 2357, 2365, and 2395, according to the synthetic-spectrum fit by Kirshner et al. (1993). The complex of iron-peak element line blending might also explain the less prominent, absorption-like feature in the SED blueward of 2500 Å at days 42 and 45. As SN 1992A suffers negligible reddening from interstellar material in both the Milky Way and the host galaxy (e.g., Wang et al. 2006; Jha et al. 2007), the observed absorption feature around 2300 Å is not caused by novel dust extinction. We suggest that the flux deficit in the F220W/uvm2 filter is likely an indication of the spectral evolution common to normal SNe Ia.

3.5. The Color Curves

Figure 13 shows the optical color curves of SN 2005cf (, , , and ), corrected for the reddening derived in §3.6. Also overplotted are the color curves of the Type Ia SNe 2001el, 2002bo, 2002dj, 2003du, and 2004S, all corrected for reddening in both the Milky Way and the host galaxies.

After a rapid decline at early phases, the color of SN 2005cf reached a minimum at  d and then became progressively redder in a linear fashion until  d, when the color curves entered a plateau phase (Fig. 13a). SN 2003du exhibited similar behavior. The overall color of SN 2005cf is redder than that of SNe 2001el and 2003du but bluer than that of SN 2004S. The scatter in at maximum can reach 0.2 mag between SNe Ia having similar values of , suggesting that a large uncertainty might be introduced when using this color index to estimate the reddening of SNe Ia.

Figure 13.— , , , and color curves of SN 2005cf compared with those of SNe 2001el, 2002bo, 2002dj, 2003du, and 2004S. All of the comparison SNe have been dereddened. The dash-dotted line shows the unreddened Lira-Phillips loci. The data sources are cited in the text.

The colors of the selected SNe (Fig. 13b) show similar evolution, except for SN 2001el near maximum and SN 2002bo at early nebular phases. We note that SN 2001el reached the bluest color slightly later, and it is also bluer than other comparison SNe Ia at this point, as with . The color of SN 2002bo after  d evolves at a faster pace than the Lira-Phillips relation because of the flatter photometric evolution in the band. This serves as a reminder that the Lira-Phillips relation does not hold for all SNe Ia, specifically the fast-expanding events (Wang et al. 2008a) and the SN 2000cx-like objects (Li et al. 2001).

The and color curves of SN 2005cf (Fig. 13c and 13d) exhibit a behavior that is quite similar to that of the normal SNe Ia. By contrasting with other normal SNe, SNe 2002bo and 2002dj are very blue in (and possibly in ), and they also reach their blue peak in about 4 d earlier.

Figure 14 shows the observed colors of SN 2005cf, together with the comparison SNe Ia corrected for reddening. The and colors are redder than the average values of the comparison SNe Ia by 0.2 mag, but the color shows little difference. As with , SNe 2002bo and 2002dj are bluer in all of the colors. We notice, however, that most of the color difference would disappear, were a smaller total-to-selective absorption ratio applied to their extinction corrections ( rather than 3.1). This suggests that either the NIR luminosities of the fast-expanding events were relatively faint with respect to the optical luminosities, or a lower value is required for their dust extinction (Wang et al., in prep.).

Figure 14.— The color curves of SN 2005cf, together with those of SNe 2001el, 2002bo, 2002dj, 2003du, and 2004S. The dashed lines represent the mean loci of the unreddened SNe Ia with –1.0 mag; the solid lines denote those with –1.3 mag (Krisciunas et al. 2004a).

The overall color evolution of SN 2005cf closely resembles the selected normal SNe Ia with similar . We notice that SNe 2002bo and 2002dj exhibit a distinguished bluer colors with =3.1.

3.6. Interstellar Extinction

The Galactic extinction toward SN 2005cf is mag (Schlegel, Finkbeiner, & Davis 1998), corresponding to a color excess of mag adopting the standard reddening law of Cardelli, Clayton, & Mathis (1989). In this section, we use several empirical methods to derive the host-galaxy reddening of SN 2005cf. All methods assume that SN 2005cf has intrinsic colors similar to those of normal SNe Ia, with either similar evolution in some colors or comparable values.

Phillips et al. (1999) proposed correlations between the light-curve width parameter and the intrinsic or values (or ). The color at early nebular phases (e.g., 30 d 90 d] was found to evolve in a similar fashion for most SNe Ia (dubbed the “Lira-Phillips relation”; Phillips et al. 1999), allowing one to statistically separate the reddening from the intrinsic color component. In addition, Wang et al. (2005) suggested using the color at 12 d after maximum [, or ] as a reddening indicator because the intrinsic value of this post-maximum color was found to be a tight function of . Based on the Lira-Phillips relation, Jha et al. (2007) also proposed to use the color at  d to measure the host-galaxy reddening of SNe Ia.

Figure 15.— Correlation between the decline rate and the observed colors for low-reddening SNe Ia. Open circles represent the sample collected from the literature (Hamuy et al. 1996; Riess et al. 1999; Riess et al. 2005; Jha et al. 2006b; Garnavich et al. 2004; Patat et al. 1996; Salvo et al. 2001; Krisciunas et al. 2004a); filled circles show those from the KAIT photometry (Ganeshalingam et al. in prep.). The observed colors of SN 2005cf, corrected for the Galactic reddening, were also overplotted (star symbol).

As shown in Figure 15, the empirical relations between the observed colors and were recalibrated using 28 well-observed, low-reddening SNe Ia49, of which 15 are from the literature and 13 are from the new KAIT photometric database (Ganeshalingam et al., in prep.). The selected SN sample closely follows the Lira-Phillips relation [e.g., with a mean slope of mag d and with the measured mag]. With the above sample, the coefficients for the relation were determined and are reported in Table 11.

Our determinations are generally comparable to the earlier results by Phillips et al. (1999), but with slightly steeper slope in and bluer unreddened zeropoints. Note that the ( correlation break down at large values; a much steeper slope is required for very fast decliners. The color does not show a great correlation with the decline rate, with a root-mean square (rms) scatter of 0.06 mag. Applying the relation to SN 2005cf, we obtain mag and mag. From the color of SN 2005cf in the nebular phase, we measured mag.

The relation was also reexamined with the new sample. The zeropoint of the intrinsic color at the nominal decline rate is bluer than in previous reports (Wang et al. 2006) by 0.08 mag. This difference is perhaps due to the stricter criteria of selecting the training sample and also indicates the difficulty of separating reddening from the intrinsic color. This post-maximum color index gives mag.

In comparison with the sample observed with other systems, the KAIT sample of 13 SNe Ia seems to be slightly bluer by 0.05 mag at  d (see the bottom panel in Fig. 15), while this difference does not hold for the other color indices shown in the same plot. Such a discrepancy may arise from systematic effects, such as the -corrections, which were found to show noticeable divergence in the nebular phase (see Fig. 3). In addition, we point out that the color may not be a constant for the fast decliners; a larger corresponds to a redder . With the new unreddened loci, we measured mag for SN 2005cf.

Krisciunas et al. (2000, 2004a) have shown that the intrinsic colors of SNe Ia are uniform and can be used as reddening indicators. Based on Krisciunas unreddened loci (see Fig. 14), for SN 2005cf we obtain mag, mag, and mag. This corresponds to an E reddening of 0.130.08 mag, 0.100.06 mag, and 0.060.06 mag, respectively.

The color excesses of SN 2005cf derived from various empirical methods are summarized in Table 12. They are consistent with each other within the uncertainties, except the color which shows larger scatter and may be not a reliable reddening color index. The mean value gives mag, indicating that SN 2005cf suffers a small but non-negligible reddening in the host galaxy.

4. Optical Spectra

There are a total of 38 optical spectra of SN 2005cf obtained at Lick Observatory and FLWO, spanning from to  d with respect to the maximum. The complete spectral evolution is displayed in Figure 16, and two late-time nebular spectra are presented in Figure 18. The earliest spectra show very broad and highly blueshifted absorption features at 3700 Å (Ca II H&K), 6020 Å (Si II 6355), and 7900 Å (Ca II NIR triplet). In particular, a flat-bottomed feature is distinctly seen in Si II 6355. The spectral evolution near maximum generally follows that of a normal SN Ia, with the distinctive “W”-shaped S II lines near 5400 Å and the blended lines of Fe II and Si II near 4500 Å. We discuss in detail the spectral evolution of SN 2005cf in the following subsections.

Figure 16.— Optical spectral evolution of SN 2005cf. The spectra have been corrected for the redshift of the host galaxy ( = 1967 km s) but not reddening, and they have been shifted vertically by arbitrary amounts for clarity. The numbers on the right-hand side mark the epochs of the spectra in days after maximum.

4.1. Temporal Evolution of the Spectra

In Figure 17, we compare the spectra of SN 2005cf with those of SNe Ia having similar at four different epochs ( d,  d, 0 d, and 18 d past maximum). All spectra have been corrected for reddening and redshift. For SN 2001el, is assumed according to the analysis by Krisciunas et al. (2007). For the other SNe, the host-galaxy reddening is measured using the empirical correlations presented in Table 11 and the extinctions are corrected using the standard value . The line identifications adopted here are taken from Branch et al. (2005, 2006).

Figure 17.— The spectrum of SN 2005cf at 11 d, 6 d, 0 d, and +18 d after maximum, overplotted with the comparable-phase spectra of SNe 1990N (Leibundgut et al. 1991), 1994D (Filippenko et al. 1997), 2001el (Wang et al. 2003; Mattila et al. 2005), 2002bo (Benetti et al. 2004), 2003du (Stanishev et al. 2007), 2004S (Krisciunas et al. 2007), and 2005cg (Quimby et al. 2006). All spectra shown here have been corrected for the reddening and redshift of the host galaxy. For clarity of display, the spectra were arbitrarily shifted in the vertical direction.

Figure 17a shows the comparison of the spectra at  d. As in the comparison SNe Ia, the absorption near 3700 Å due to the blending of Ca II H&K and Si II 3858 is prominent in the earliest spectrum of SN 2005cf. The Si II 4130 absorption feature appears common in the early spectra, except in the spectrum of SN 1990N. In the 4000–4500 Å wavelength range, all of the SNe show a strong absorption feature at 4300 Å, probably owing to a blend of Mg II 4481 and Fe III 4404. The weak Si III 4553, 4568 blend can be identified in the comparison SNe, though its absence in SN 2002bo may indicate a cooler temperature in the photosphere. The “W”-shaped feature of the two S II lines appears at this phase. The lines of Si II 6355 and the Ca II NIR triplet of SN 2005cf are very broad and deep, comparable to those in SNe 2001el and 2002bo. One interesting feature is the flat-bottomed profile of Si II 6355, which was previously only observed in SN 1990N at  d and in SN 2001el at  d. In contrast, SNe 2003du and 2005cg displayed a triangular-shape feature at similar phases.

Figure 17b shows the comparison at  d. A second minimum begins to develop on the red side of the Ca II H&K absorption, as in SN 2003du. The weak features (e.g., Si II 4130, Si III 4560, and the S II “W”) strengthen with time. The flat-bottomed feature associated with Si II 6355 is barely visible in the SN 2005cf spectrum, with only a small notch on the blue side of the absorption minimum. The Ca II NIR triplet now weakens and shows a double minimum on the red side of the main absorption.

In Figure 17c, we compare the spectrum of SN 2005cf near maximum with those of SNe 2001el, 2002bo, 2003du, and 2004S. At  d, the spectrum of SN 2005cf has evolved while maintaining most of its characteristics shown at earlier epochs. The second absorption minimum in Ca II H&K now becomes noticeable in SNe 2005cf and 2003du, while it is still barely observed in SN 2004S. (The spectrum of SN 2001el did not cover this wavelength range.) The Si II 6355 absorption in SN 2005cf now appears quite similar to that of the other normal SNe Ia. The O I 7773 line strengthens in all cases in our sample. The two absorption components of the Ca II NIR triplet evolve rapidly, with the blue component becoming weak and the red one gaining strength in the minimum, similar to SNe 2001el and 2004S. SN 2002bo still shows broader and deeper absorptions of Si II 6355 and the Ca II NIR triplet with less substructure. We measured the line-strength ratio of Si II 5958, 5979 to Si II 6355, known as (Si II) (Nugent et al. 1995), to be for SN 2005cf near maximum, in good agreement with the measurement reported by G07.

In Figure 17d, we compare the spectra at  d. SN 2005cf exhibits spectral evolution quite similar to that of the other SNe Ia. The Fe II and Si II features are fairly developed in the range 4700–5000 Å. The stronger Fe II lines dominate around 5000Å, and Na I D appears in the region overlapping with Si II 5972. The Si II 6355 trough becomes affected by Fe II 6238, 6248 and Fe II 6456, 6518. Although the Ca II NIR triplet shows the most diverse features at the earlier epochs, they develop into a rather smooth absorption profile by 2 weeks after maximum.

Comparison of the spectra of SNe Ia having similar values reveals that they show the most diversity at the earliest epochs, with significantly different strengths and profiles of the main features (e.g., Si II 6355 and the Ca II NIR triplet). In general, the overall spectral evolution of SN 2005cf at early phases closely resembles that of SN 2001el.

Figure 18.— Late-time nebular spectra of SN 2005cf, slightly smoothed. The nebular spectra of SN 2003du (Stanishev et al. 2007) and SN 2002dj (Pignata et al. 2008) at about the same phase as the earlier SN 2005cf spectrum are shown for comparison. Both reddening and redshift corrections have been applied to the spectra.

Two late-time nebular Keck spectra, obtained with LRIS on day +319 and with DEIMOS on day +614, are shown in Figure 18. They do not exhibit any detectable signature of a low-velocity hydrogen emission, though the S/N is low, especially in the case of the day +614 spectrum. (See also the deep observations of SN 2005cf performed by Leonard 2007.) The spectrum on day +319 is dominated by the forbidden lines of singly and doubly ionized Fe and Co lines; its overall shape is very similar to that of SN 2003du at a similar phase. The nebular spectrum of SN 2002dj at this phase is also quite normal, without showing extra flux (or an evidence for presence of an echo) at shorter wavelengths as in the extreme HV event SN 2006X (Wang et al. 2008b). We note, however, that SN 2002dj is a slightly fast-expanding object with less significant reddening (Pignata et al. 2008).

4.2. The Photospheric Expansion Velocity

Figure 19.— Evolution of the expansion velocity of SN 2005cf as measured from the minimum of Si II 6355 and S II 5640, compared with the values of SNe 1990N, 1994D, 1998aq, 2001el, and 2003du (see text for the references). The grey dots show the low-velocity component decomposed from the Si II 6355 absorption of SN 2005cf by using the double-Gaussian model (see §4.3.1 and Fig.20); the open circles represent the detached high-velocity component. Overplotted are velocities predicted by the Lentz et al. (2000) model for cases of 10 (dashed line), 3 (dotted line), and 1/3 (solid line) solar C + O layer metallicity.

In this paper, we examine the photospheric expansion velocity from the velocity evolution of the Si II 6355 and S II 5640 lines. The derived values of SN 2005cf from Si II 6355 and S II 5640 as a function of time are shown in Figure 19, together with those of the comparison SNe Ia. The measurements from the spectra published by G07 are also overplotted (small filled circles). All velocities have been corrected for the redshifts of the host galaxies.

At the earliest phases, the photospheric expansion velocity implied from Si II 6355 for SN 2005cf is higher than that for SNe 1990N (Leibundgut et al. 1992), 1998aq (Branch et al. 2003), and 2003du (Stanishev et al. 2007) by 2000 km s, and comparable to that for SNe 1994D (Filippenko 1997, Patat et al. 1996) and 2001el (Wang et al. 2003; Mattila et al. 2005). This expansion velocity declines very rapidly within the first two weeks before maximum and then maintains a plateau phase for about a month. Such evolution may be related to the fact that the Si II absorption region is close to the photosphere at earlier phases but becomes more detached at later times (Patat et al. 1996). In contrast, the velocity yielded from the S II 5640 line is slightly lower than that of the other SNe Ia and shows a flat evolution from  d to 5 d. SN 2001el may show a similar plateau feature, though the data are sparse.

Following Benetti et al. (2005), we calculate the velocity gradient of Si II 6355 for SN 2005cf as km s d during the period –30 d, which puts SN 2005cf in the group of normal SNe Ia having low velocity gradients (LVGs).

4.3. The High-Velocity Features

In addition to the evolution of the photospheric expansion, the well-sampled spectra of SN 2005cf (especially those at earlier phases) provide a good opportunity to study the high-velocity (HV) features that were only seen in the earliest spectra. The HV material is usually located in the outermost layers of the ejecta where SNe Ia show the highest degree of heterogeneity.

The High-Velocity Si II

Figure 20 (see the left panel) shows the pre-maximum evolution of the velocity-space distribution of Si II 6355 in the spectra of SN 2005cf. In the 12 d spectrum, this absorption profile is broad and asymmetric with a stronger minimum on the blue side. At  d, the Si II line exhibits a flat-bottomed feature with comparable absorption minima on both red and blue sides. As the spectrum evolves, the red-side minimum gradually dominates. By  d, the Si II absorption feature gradually develops into a single minimum with a typical velocity of 10,500 km s, though the line profile may still be affected by the blue component until around maximum light (G07).

The observed line profiles of Si II 6355 at earlier phases can be well fit by a double-Gaussian function with separate central wavelengths, probably suggesting the presence of another HV absorption component. The HV component could be a thin pure Si shell or a mixed layer of Si II and C II 6580 (Fisher et al. 1997; Mazzali et al. 2001, 2005). Assuming that the blue-side absorption component is primarily produced by the HV Si II detached from the photosphere, the mean absorption-minimum velocity is estimated to be km s during the period from  d to  d (see also the open circles in Fig.19). This velocity is much higher than the value inferred from the absorption minimum on the red side.

The presence of HV Si II in SN 2005cf was also proposed by G07 by modeling the observed spectra with the use of the parameterized code for supernova synthetic spectroscopy, SYNOW (Fisher 2000). Their analysis suggested that the HV feature of Si II 6355 in SN 2005cf is detached at 19,500 km s. Given the contamination by such a HV Si II feature, the photospheric velocity measured directly from the overall line profile was overestimated. The recomputed values from the Si II line (see the gray dots in Fig. 19), after removing the HV component, closely match the velocity evolution predicted from the 1/3 solar metallicity models by Lentz et al (2000).

Figure 20.— Left Panel: The evolution in velocity space of Si II 6355 in SN 2005cf compared with the double-Gaussian fit. Dashed green lines show the velocity distribution on the blue side, and dotted blue lines show the component on the red side. The red solid lines represent the best-fit curve to the observed profile. Right Panels: Comparison of pre-maximum evolution of the Si II 6355 profile of SN 2005cf with that of SNe 1990N, 1999ee, 2001el, 2003du, and 2005cg at four selected epochs (see text for the references).

In the right panels of Figure 20, we also compare the Si II absorption features in the earliest spectra. The presence of the HV feature of Si II has also been suggested in SNe 1990N, 1999ee, 2001el, and SN 2005cg (Mazzali et al. 2001; Mattila et al. 2005; Quimby et al. 2006), but none of them could be securely established due to the sparse coverage of the pre-maximum spectra. Of the above SNe Ia, the flat-bottomed profile of the Si II line is seen only in SN 1990N at  d and SN 2001el at  d. Inspection of the  d spectrum of SN 2003du reveals a Si II absorption reminiscent of the feature seen in SN 2005cf at  d. A triangular-shaped profile is present in the spectra of all the other events. It is therefore likely that such a “peculiar” line profile is just a snapshot of the common evolutionary pattern (see similar arguments by Stanishev et al. 2007).

In addition to the absorption by the HV material, alternative interpretations have also been proposed for the formation of the broad profile of Si II absorption. Mattila et al. (2005) suggest that the flat-bottomed line shape in SN 2001el can be produced by pure scattering within a thin region moving at the continuum photospheric velocity; it disappears as the photosphere recedes and the scattering region widens. The ejecta slowly extending to the HV part, typical for delayed-detonation models (Khokhlov 1991), may also account for the triangular feature of the Si II profile in SN 2005cg (Quimby et al. 2006). However, neither of these two models can explain the asymmetric line profile with a stronger HV component, as observed in SN 2005cf at  d and in SN 1999ee at  d (Hamuy et al. 2002)(see the top right panel of Fig. 20).

The High-Velocity Ca II

Figure 21 presents the detailed evolution of the Ca II NIR triplet and Ca II H&K of SN 2005cf. In comparison with the Si II line, the HV features in the Ca II NIR triplet are more frequently observed in SNe Ia (e.g., Mazzali et al. 2005), as they are more pronounced and may have a longer duration. The HV component dominates in the Ca II NIR lines at earlier phases, but it gradually loses its strengths with time. In the Ca II NIR triplet, the HV components are more separated from the photospheric components than in the Si II line. At  d, the HV component shows an expansion velocity at about 22,000 km s. By  d, the velocity is around 19,000 km s and the absorption minimum is beginning to be dominated by the photospheric component at 10,000 km s.

Figure 21.— Premaximum evolution in velocity space for the Ca II H&K and NIR triplet of SN 2005cf. Vertical dashed lines indicate, respectively, the highest velocity in the earliest phase ( 23000 km s) and the photospheric velocity (at 11000 km s).

The Ca II H&K lines may show similar HV features, but they overlap with the Si II 3858 line at earlier phases. Due to the severe line blending, it is difficult to disentangle the HV component and quantify its strength. Assuming a double-Gaussian model, we measure the velocity of the HV component at 24,500 km s and 20,000 km s in the  d and  d spectra, respectively, similar to those measured for the Ca II NIR triplet. The higher velocity of the HV component in the Ca II lines with respect to the Si II line perhaps suggests a different abundance distribution in the ejecta.

Origin for the HV features

Currently, the origin of the HV features is still debated. In principle, their formation can be due to an abundance and/or a density enhancement in the ejecta at outer layers. According to Mazzali et al. (2005), the single abundance enhancement may not account for the observed HV features, as the nuclear burning cannot produce enough Si and Ca required in the outer region. In contrast, an enhancement in the local density could lead to a good reproduction of the HV spectral evolution, as demonstrated by the three-dimensional (3D) explosion models (e.g., Ropke et al. 2006). One possible scenario for the density enhancement is the interaction of the outermost ejecta with the circumstellar matter (CSM) produced in the vicinity of the SN (e.g., Gerardy et al. 2005). On the other hand, an aspherical ejecta model could also cause the HV density enhancement. Variations of the strength of the HV features may be explained by different viewing angles if they result from aspherical structures like a torus or clumps (Tanaka et al. 2006).

Inspection of the early-time spectra presented in Figure 17 reveals that the strength of the HV features from Si II and Ca II may be correlated in a given SN, though their strength varies from SN to SN. This holds true for SN 2005cf and all the comparison objects, perhaps favoring the origin of the observed HV features from either CSM interaction or aspherical structure of the ejecta produced by the explosion itself. Note that the detached HV features discussed here seem different from those observed in SN 2006X or even in SN 2002bo; however, the same configuration with a much larger photospheric velocity may explain the difference (Tanaka et al. 2008).

5. The Distance and Luminosity of SN 2005cf

The extensive photometric observations of SN 2005cf, from the UV to the NIR bands, enable us to construct the “bolometric” light curve within 0.2–2.4 m. For this calculation, we used the normalized passband transmission curves given by Bessell (1990). The integrated flux in each filter was approximated by the mean flux multiplied by the effective width of the passband, and was corrected for the reddening. Since the filter transmission curves do not continuously cover the spectrum and some also overlap, we corrected for these gaps and overlaps by adjusting the effective wavelengths of the filters in the UV, optical, and NIR passbands.

5.1. The Distance to SN 2005cf

The distance to SN 2005cf is important for deriving the bolometric luminosity. Direct measurements were unavailable in the literature, so we used several methods to estimate the distance. According to Wang et al. (2006), a nominal standard SN Ia with Cepheid-based calibration has an absolute magnitude of mag in the band. Combining this value with the fully corrected apparent magnitude of SN 2005cf, we obtain a distance modulus mag. We also determine the distance using the latest version of the MLCS2k2 fitting technique (Jha et al. 2007), which yields mag.

Krisciunas et al. (2004b) propose that SNe Ia are more uniform in the NIR bands than in the optical; their NIR peak luminosities are found to be nearly independent of the light-curve shape. The absolute NIR peak magnitudes for SNe Ia with are reported as 18.61 in , 18.28 in , and 18.44 mag in , respectively. Assuming the same NIR magnitudes for SN 2005cf, we derive a mean distance modulus mag.

Averaging the above three distances, we obtain a weighted mean of mag for SN 2005cf. Note that this estimate may still suffer from an additional uncertainty of 0.12–0.15 mag, due to the intrinsic luminosity dispersion of SNe Ia in both optical and NIR bands (Krisciunas et al. 2004; Wang et al. 2006; Wood-Vasey et al. 2007b).

5.2. The Missing Flux Below the Optical Window

The filled circles in Figure 22 show the temporal evolution of the ratio of the NIR-band emission (9000–24,000 Å) to the optical (3200–9000 Å), . The flux ratios obtained from SNe 2001el and 2004S are overplotted. The dashed curve in the plot represents the best fit to the data of SN 2005cf. In the fit, the NIR contribution at  d is assumed to be the same as that of SN 2001el and SN 2004S. This assumption is reasonable because the ratio of SN 2005cf agrees well with the corresponding values of these two SNe Ia from the very beginning to  d. Initially, the ratio shows a sharp decline with a minimum 4 d after the maximum. Then it rises rapidly in a linear fashion and reaches a peak (20%) at  d, when the secondary maximum appears in the NIR. At nebular phases, the NIR contribution gradually declines and becomes 10% at  d, similar to that found by Suntzeff in studying SN 1992A (1996).

The contribution of the UV flux in the 1600–3200 Å range to the optical is shown with the open circles in Fig. 22. The dotted line indicates the best fit to the observed data points, assuming that the UV flux remains constant at  d. A flat contribution at late times was evidenced by the UV data of SN 2001el from the HST archive (see Fig. 14 in Stanishev et al. 2007). The UV contribution is found to be generally a few percent of the optical in SN 2005cf, with a peak (10%) at around the maximum. Three weeks after the maximum, the ratio remains at a level of 3–4%.

Figure 22.— The ratio of the UV and NIR fluxes to the optical for SN 2005cf. Overplotted are the NIR flux ratios of SNe 2001el and 2004S.

It is also interesting to estimate the ratios of the optical fluxes to the bolometric fluxes, as most SNe Ia were not observed in the UV or the NIR bands. These ratios are useful for correcting the observed optical luminosity to the bolometric luminosity. Figure 23 shows the correction factors (defined as the missing fraction of the observed flux relative to the generic bolometric luminosity) obtained from SN 2005cf; one can see that the bolometric luminosity is dominated by the optical fluxes. The missing flux beyond the optical window is about 20%, with a slightly larger fraction at  d due to the appearance of the secondary maximum in the NIR. The corrections, based on the fluxes in the , , , , and bands, are also shown in the plot. We note that the bolometric correction for the filter exhibits the least variation with time: the overall variation is less than 4% before  d, and at later phases the correction stays nearly constant. This validates previous assumptions that the -band photometry can well represent the bolometric light curve, in particular at later phases, at a constant fraction of about 20%.

Figure 23.— Correction factors for missing passbands. The correction factors are obtained by comparing the fluxes in the passbands with the total flux.

5.3. The Bolometric Light Curve

Figure 24 shows the “” bolometric light curves of SN 2005cf and several other SNe Ia. The UV emission of all the comparison SNe was corrected on the basis of SN 2005cf. Similar corrections were applied to their light curves when the NIR observations are missing. The distances to the comparison SNe Ia were derived using the methods adopted in §5.1. The bolometric light curves of our SN Ia are overall very similar in shape, with the exceptions of SN 2002bo and SN 2002dj, which seem to rise at a faster pace. The maximum bolometric luminosity of SN 2005cf is estimated to be erg s around the -band maximum, which is similar to that of SNe 2001el and 2003du but less than that of SNe 2002bo and 2002dj. However, differences in the bolometric luminosity at maximum may be due to errors in the absorption corrections and/or the distance modulus.

Figure 24.— The bolometric light curve of SN 2005cf. Overplotted are the corresponding light curves of the comparison SNe Ia. The number in parentheses represent the values for the SNe Ia.

With the derived bolometric luminosity, we can estimate the synthesized Ni mass — one of the primary physical parameters determining the peak luminosity, the light curve width, and the spectroscopic evolution of SNe Ia (e.g., Kasen et al. 2006). Assuming the Arnett law (Arnett 1982; Arnett et al. 1985; Branch 1992), the maximum luminosity produced by the radioactive Ni can be written as (Stritzinger & Leibundgut 2005)

(1)

where is the rise time of the bolometric light curve, and is the Ni mass (in units of solar masses, M). With the photometric data in the band and our earliest unfiltered data from the database of the KAIT survey, we estimate the rise time to the maximum as  d. Inserting this value and the maximum bolometric luminosity into the above equation, we derive a nickel mass of M for SN 2005cf. This is within the reasonable range of Ni masses for a normal SN Ia. The quoted error bar includes uncertainties in the rise time and in the peak luminosity.

The lower bolometric luminosity and smaller nickel mass obtained by P07 is primarily due to the neglected host-galaxy extinction for SN 2005cf in their analysis. Table 13 lists all of the important parameters for SN 2005cf and its host galaxy, as we derived in the previous sections.

6. Discussion and Conclusions

In this paper we present extensive optical, UV, and NIR photometry as well as optical spectroscopy of SN 2005cf. In particular, the photometric observations in the optical bands were extremely well-sampled with numerous telescopes. To minimize systematic deviations from the standard system, we carefully computed the -corrections and applied them to SN 2005cf. Photometry without such corrections may potentially lead to a noticeably inconsistent measurement of the reddening, which makes precise extinction corrections difficult.

The Swift UVOT optical photometry is found to be consistent with the ground-based observations to within 0.05 mag, after applying the -corrections. The Swift UVOT UV uvm2 and uvw2 photometry is relatively close to that of HST ACS F220W and F250W, respectively, with a small shift of up to 0.1–0.2 mag.

Our observations show that SN 2005cf is a normal SN Ia with a typical luminosity decline rate (true) = mag. Based on the colors and the refurbished Color- relations, we estimated the host-galaxy reddening of mag, which is small but non-negligible. The NIR light curves closely resemble those of normal SNe Ia, with a prominent secondary maximum. One distinguishing feature is the UV luminosity in the 2000–2500 Årange which appears much fainter and peaks later than that of the neighboring bands. This is likely caused by intrinsic spectral features in the UV, an explanation favored by the evolution of the SED.

The comprehensive data, from UV to NIR bands, allow us to establish the bolometric light curve of SN 2005cf in the 1600–24,000 Å range. The maximum bolometric luminosity is found to be erg s, corresponding to a synthesized nickel mass of  M. The bolometric luminosity is dominated by the optical emission; the UV contribution is found to be a few percent of the optical, and the peak value (10%) occurs at around maximum light. The NIR flux contribution shows more complicated temporal evolution: the ratio decreases from the beginning of the explosion and reaches a minimum of 5% at  d; it then rises up to a peak value of 20% at  d, and finally declines in a linear fashion.

In general, the optical spectra of SN 2005cf are similar to those of normal SNe Ia. Strong HV features are distinctly present in the Ca II NIR triplet and the Ca II H&K lines; these are detached from the photosphere at a velocity 19,000-24,000 km s. A HV Ca II feature is commonly seen in other SNe Ia, while the flat-bottomed shape of the Si II 6355 line is relatively rare perhaps due to the paucity of the very early spectra. The excellent temporal coverage of the spectra of SN 2005cf reveals that either the flat-bottomed feature or the triangular-shaped feature associated with Si II 6355 in some SNe Ia might be due to contamination by another HV absorption component, such as the pure Si II shell.

Although HV absorptions of Ca II and Si II are observed in many SNe Ia, they diverge in strength and duration. For instance, the HV features are very strong in SN 2005cf and SN 2001el, remaining until a few days after maximum, whereas they are relatively weak in SN 2003du and SN 2005cg and becomes marginally detectable around maximum. Given a common origin of the HV absorption from the aspherical ejecta (e.g., a torus or clumps), the diversity in strength of the HV features could be interpreted by a line-of-sight effect (see also Tanaka et al. 2006). Aspherical structure of the ejecta is favored by the evidence that the degree of polarization for the line features in SN 2001el is much higher than that for the continuum (Wang et al. 2003; Kasen et al. 2003; see also Chornock & Filippenko 2008 for SN 2004S). It is thus interesting to examine whether the strength of the HV line features correlates, at least for a subset of SNe Ia, with that of the line polarization. Unfortunately, similar high-quality polarimetric measurements at early phases are sparse for SNe Ia (but see Wang et al. 2007). Obviously, polarization spectra obtained from the very beginning would allow us to penetrate the layered geometrical structure of the SN ejecta as well as the immediate environment surrounding the explosion site.

The well-observed, multi-wavelength data presented in this paper makes SN 2005cf a rare ”golden standard” sample of normal type Ia supernova, which could be used as a testbed either for the theoretical models of SN Ia, or for the studies of the systematic errors in SN Ia cosmology.

We thank Ryan Chronock and Stefanie Blondin for useful discussions. Some of the data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration (NASA). The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. We thank the the Lick Observatory, Palomar Observatory, NAOC, and CTIO staffs for their assistance with the observations. The research of A.V.F.’s supernova group at UC Berkeley is supported by NSF grant AST–0607485, the TABASGO Foundation, Gary and Cynthia Bengier, and Department of Energy grant DE-FG02-08ER41563. Additional support was provided by NASA grant GO–10182 from the Space Telescope Science Institute (STScI), which is operated by AURA, Inc., under NASA contract NAS5-26555. We are also grateful to the National Natural Science Foundation of China (NSFC grant 10673007), the 973 Key Program of China (2009CB824800), and the Basic Research Funding at Tsinghua University (JCqn2005036). Supernova research at Harvard University is supported by NSF grant AST06-06772. M.M. is supported by a fellowship from the Miller Institute for Basic Research The work of AG is supported by grants from the Israeli Science Foundation and the EU Marie Curie IRG program, and by the Benoziyo Center for Astrophysics, a research grant from the Peter and Patricia Gruber Awards, and the William Z. and Eda Bess Novick New Scientists Fund at the Weizmann Institute. KAIT and its ongoing operation were made possible by donations from Sun Microsystems, Inc., the Hewlett-Packard Company, AutoScope Corporation, Lick Observatory, the NSF, the University of California, the Sylvia & Jim Katzman Foundation, and the TABASGO Foundation. The PAIRITEL project is operated by the Smithsonia Astrophysical Observatory (SAO) and was made possible by a grant from the Harvard University Milton Fund, a camera loan from the University of Virginia and continued support of the SAO and UC Berkeley. PAIRITEL is further supported by the NASA/ Guest Investigator grant NNG06GH50G. The CTIO 1.3 m telescope is operated by the Smart and Moderate Aperture Research Telescope System (SMARTS) Consortium. We are particularly grateful for the scheduling flexibility of SMARTS. The Liverpool Telescope is operated on the island of La Palma by Liverpool John Moores University in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias with financial support from the UK Science and Technology Facilities Council. We made use of the NASA/IPAC Extragalactic Database (NED), which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with NASA.
Telescope
KAIT 0.76 m 0.085(017) 0.043(011) 0.035(007) 0.070(012) 0.010(006)
FLWO 1.2 m 0.037(003) 0.080(003) 0.039(002) 0.207(010) 0.109(008)
CTIO 1.3 m 0.035(001) 0.049(005) 0.029(009) 0.070(006)
CTIO 0.9 m 0.100(004) 0.096(011) 0.016(001) 0.006(001) 0.006(001)
Palomar 1.5 m 0.100(011) 0.020(007) 0.070(012) 0.040(006)
Lick 1.0 m 0.080(010) 0.080(011) 0.060(007) 0.100(012) 0.035(006)
Liverpool 2.0 m 0.045(004) 0.054(005) 0.200(008) 0.100(004)
TNT 0.8 m 0.132(004) 0.080(004) 0.106(006) 0.037(003)
50
Table 1Instrumental Color Terms for Different Telescopes
Star
1 15.265(010) 14.380(007) 13.877(006) 13.493(093)
2 13.650(030) 13.486(012) 12.799(013) 12.417(076) 12.035(017)
3 16.370(030) 15.625(008) 14.676(012) 14.086(002) 13.560(008)
4 16.582(030) 16.466(008) 15.756(007) 15.349(008) 14.947(014)
5 15.311(030) 15.328(011) 14.820(011) 14.519(005) 14.199(002)
6 14.014(030) 14.059(027) 13.604(014) 13.329(005) 13.037(019)
7 18.297(030) 18.434(017) 17.786(001) 17.518(020) 17.156(025)
8 18.926(030) 17.810(020) 16.264(007) 15.236(007) 14.048(007)
9 15.831(030) 15.660(023) 14.986(010) 14.597(007) 14.248(023)
10 18.294(030) 17.124(016) 15.947(011) 15.155(012) 14.488(018)
11 14.956(030) 14.747(008) 14.022(005) 13.594(001) 13.201(017)
12 19.353(030) 18.338(012) 17.327(017) 16.708(009) 16.205(025)
13 15.340(030) 14.760(006) 13.883(006) 13.337(005) 12.823(015)
14 18.558(030) 18.139(025) 17.393(027) 16.925(030) 16.451(019)
15 18.297(030) 17.591(011) 16.715(007) 16.187(005) 15.756(011)
16 17.933(030) 17.981(020) 17.450(015) 17.107(039) 16.724(074)
51
Table 2Magnitudes of Photometric Standards in the SN 2005cf Field52
UT Date JD2,450,000 Phase53 Instrument54
2005 May 31 3521.75 -11.91 15.862(0.038) 15.600(0.022) 15.346(0.022) 15.189(0.032) 15.360(0.041) 2
2005 May 31 3521.77 -11.89 15.850(0.038) 15.579(0.029) 15.293(0.024) 15.206(0.041) 15.312(0.041) 1
2005 Jun 1 3522.74 -10.92 15.360(0.035) 15.151(0.022) 15.000(0.022) 14.838(0.032) 15.062(0.041) 2
2005 Jun 1 3522.87 -10.79 15.254(0.035) 15.096(0.022) 14.955(0.022) 14.846(0.032) 14.953(0.041) 1
2005 Jun 1 3523.15 -10.51 15.054(0.041) 14.954(0.032) 14.793(0.032) 14.896(0.041) 3
2005 Jun 2 3523.77 -9.89 14.851(0.035) 14.774(0.022) 14.721(0.022) 14.474(0.032) 14.701(0.041) 2
2005 Jun 2 3523.87 -9.79 14.768(0.035) 14.765(0.022) 14.670(0.022) 14.536(0.032) 14.651(0.041) 1
2005 Jun 2 3524.13 -9.53 14.751(0.022) 14.654(0.022) 14.488(0.032) 14.573(0.041) 3
2005 Jun 3 3524.63 -9.03 14.587(0.022) 14.497(0.022) 14.411(0.032) 14.464(0.041) 4
2005 Jun 3 3524.68 -8.98 14.543(0.022) 14.502(0.022) 14.291(0.032) 14.487(0.041) 2
2005 Jun 3 3524.79 -8.87 14.512(0.022) 14.489(0.022) 14.326(0.032) 14.409(0.041) 5
2005 Jun 3 3524.85 -8.81 14.380(0.035) 14.494(0.022) 14.438(0.022) 14.298(0.032) 14.407(0.041) 1
2005 Jun 3 3525.42 -8.24 14.343(0.024) 14.344(0.022) 14.190(0.032) 14.269(0.041) 6
2005 Jun 4 3525.69 -7.97 14.154(0.035) 14.304(0.022) 14.293(0.022) 14.079(0.032) 14.259(0.041) 2
2005 Jun 4 3525.76 -7.90 14.293(0.022) 14.299(0.022) 14.128(0.032) 14.199(0.041) 5
2005 Jun 4 3525.87 -7.79 14.274(0.022) 14.247(0.022) 14.095(0.032) 14.217(0.041) 7
2005 Jun 5 3526.68 -6.98 14.127(0.022) 14.122(0.022) 13.916(0.032) 14.108(0.041) 2
2005 Jun 5 3526.75 -6.91 13.883(0.035) 14.101(0.022) 14.118(0.022) 5
2005 Jun 5 3527.44 -6.22 14.007(0.022) 14.003(0.022) 13.875(0.032) 13.948(0.041) 6
2005 Jun 6 3527.64 -6.02 14.014(0.022) 13.992(0.022) 13.884(0.032) 13.948(0.041) 4
2005 Jun 6 3527.69 -5.97 13.734(0.035) 13.979(0.022) 13.981(0.022) 13.785(0.032) 13.970(0.041) 2
2005 Jun 6 3527.85 -5.81 13.655(0.035) 13.950(0.022) 13.942(0.022) 13.796(0.032) 13.915(0.041) 1
2005 Jun 6 3528.43 -5.23 13.863(0.022) 13.896(0.022) 13.781(0.032) 13.845(0.041) 6
2005 Jun 7 3528.75 -4.91 13.861(0.022) 13.852(0.022) 13.708(0.032) 13.863(0.041) 7
2005 Jun 7 3528.84 -4.82 13.564(0.035) 13.843(0.022) 13.843(0.022) 13.697(0.032) 13.828(0.041) 1
2005 Jun 8 3529.43 -4.23 13.755(0.025) 13.795(0.022) 13.704(0.032) 13.765(0.041) 6
2005 Jun 8 3529.71 -3.95 13.527(0.035) 13.768(0.022) 13.783(0.022) 13.683(0.032) 13.778(0.041) 8
2005 Jun 8 3530.42 -3.24 13.716(0.022) 13.736(0.022) 13.629(0.032) 13.774(0.041) 6
2005 Jun 8 3530.59 -3.07 13.741(0.022) 13.712(0.022) 13.644(0.032) 13.755(0.041) 4
2005 Jun 9 3530.68 -2.98 13.433(0.035) 13.718(0.022) 13.713(0.022) 13.558(0.032) 13.786(0.041) 2
2005 Jun 10 3531.67 -1.99 13.395(0.035) 13.677(0.022) 13.655(0.022) 13.523(0.032) 13.783(0.041) 2
2005 Jun 10 3531.79 -1.87 13.666(0.022) 13.630(0.022) 13.551(0.032) 13.767(0.041) 7
2005 Jun 10 3531.83 -1.83 13.422(0.035) 13.664(0.022) 13.639(0.025) 13.577(0.032) 13.767(0.041) 1
2005 Jun 10 3532.42 -1.24 13.654(0.022) 13.638(0.022) 13.550(0.032) 13.745(0.041) 6
2005 Jun 11 3532.87 -0.79 13.403(0.035) 13.643(0.022) 13.600(0.022) 13.548(0.032) 13.766(0.041) 1
2005 Jun 11 3533.42 -0.24 13.621(0.021) 13.595(0.022) 13.559(0.032) 13.772(0.041) 6
2005 Jun 12 3533.66 0 13.650(0.022) 13.592(0.022) 13.578(0.032) 13.748(0.041) 4
2005 Jun 12 3533.72 0.06 13.623(0.022) 13.570(0.022) 13.515(0.032) 13.785(0.041) 7
2005 Jun 12 3533.84 0.18 13.393(0.035) 13.619(0.022) 13.568(0.022) 13.517(0.032) 13.761(0.041) 1
2005 Jun 13 3534.73 1.07 13.444(0.035) 13.637(0.022) 13.574(0.022) 13.485(0.032) 13.821(0.041) 2
2005 Jun 13 3534.84 1.18 13.412(0.035) 13.622(0.022) 13.549(0.022) 13.525(0.032) 13.773(0.041) 1
2005 Jun 13 3535.43 1.77 13.649(0.022) 13.581(0.022) 13.540(0.032) 13.787(0.041) 6
2005 Jun 14 3535.72 2.06 13.641(0.022) 13.564(0.022) 13.505(0.032) 13.812(0.041) 7
2005 Jun 14 3535.74 2.08 13.489(0.035) 13.654(0.022) 13.574(0.022) 13.496(0.032) 13.858(0.041) 2
2005 Jun 14 3535.83 2.17 13.487(0.035) 13.631(0.022) 13.556(0.032) 13.509(0.032) 1
2005 Jun 14 3536.44 2.78 13.719(0.021) 13.591(0.022) 13.539(0.032) 13.800(0.041) 6
2005 Jun 15 3536.70 3.04 13.564(0.035) 13.702(0.022) 13.581(0.022) 13.519(0.032) 13.884(0.041) 2
2005 Jun 15 3536.83 3.17 13.563(0.035) 13.681(0.022) 13.558(0.022) 13.545(0.032) 13.840(0.041) 1
2005 Jun 15 3537.47 3.81 13.717(0.022) 13.616(0.022) 13.551(0.032) 13.833(0.041) 6
2005 Jun 16 3537.82 4.16 13.554(0.022) 13.527(0.032) 13.814(0.041) 1
2005 Jun 17 3538.68 5.02 13.815(0.022) 13.624(0.022) 13.638(0.032) 13.884(0.041) 4
2005 Jun 21 3542.61 8.95 14.093(0.045) 13.733(0.022) 13.813(0.032) 14.059(0.041) 4
2005 Jun 21 3542.72 9.06 14.117(0.054) 14.090(0.022) 13.740(0.022) 13.789(0.032) 14.117(0.041) 1
2005 Jun 21 3542.76 9.10 14.040(0.035) 13.709(0.033) 13.742(0.032) 14.093(0.041) 7
2005 Jun 21 3543.06 9.40 13.717(0.031) 13.795(0.032) 14.143(0.053) 3
2005 Jun 22 3543.68 10.02 14.216(0.035) 14.171(0.022) 13.797(0.022) 13.814(0.032) 14.171(0.041) 2
2005 Jun 22 3543.82 10.16 14.219(0.035) 14.182(0.022) 13.808(0.022) 13.868(0.032) 14.168(0.041) 1
2005 Jun 23 3544.77 11.11 14.217(0.021) 13.867(0.027) 13.888(0.032) 14.197(0.041) 7
2005 Jun 23 3544.80 11.14 14.299(0.035) 14.278(0.023) 13.866(0.032) 13.941(0.035) 14.248(0.041) 1
2005 Jun 24 3545.82 12.16 14.429(0.035) 14.377(0.022) 13.894(0.029) 14.013(0.032) 14.297(0.041) 1
2005 Jun 25 3546.75 13.09 14.539(0.035) 14.465(0.026) 13.946(0.034) 14.054(0.034) 14.328(0.041) 1
2005 Jun 26 3547.67 14.01 14.553(0.022) 14.015(0.022) 14.141(0.032) 14.336(0.041) 4
2005 Jun 26 3547.82 14.16 14.682(0.035) 14.570(0.022) 14.002(0.022) 14.103(0.032) 14.343(0.041) 1
2005 Jun 27 3548.66 15.00 14.841(0.037) 14.647(0.022) 14.071(0.022) 14.117(0.032) 14.400(0.041) 2
2005 Jun 27 3548.79 15.13 14.828(0.036) 14.670(0.037) 14.053(0.027) 14.154(0.032) 14.347(0.041) 1
2005 Jun 28 3549.71 16.05 14.99 (0.035) 14.778(0.022) 14.134(0.022) 14.161(0.032) 14.402(0.041) 2
2005 Jun 28 3549.74 16.08 14.755(0.022) 14.118(0.023) 14.168(0.032) 14.309(0.041) 7
2005 Jun 28 3549.79 16.13 14.983(0.035) 14.781(0.022) 14.119(0.029) 14.200(0.039) 14.349(0.041) 1
2005 Jun 29 3550.66 17.00 15.141(0.035) 14.879(0.022) 14.178(0.022) 14.161(0.032) 14.371(0.041) 2
2005 Jun 29 3550.67 17.01 14.911(0.022) 14.195(0.022) 14.251(0.032) 14.340(0.041) 4
2005 Jun 29 3550.79 17.13 15.082(0.035) 14.879(0.021) 14.162(0.022) 14.196(0.032) 14.332(0.041) 1
2005 Jun 29 3551.49 17.83 14.913(0.032) 14.222(0.022) 14.217(0.032) 14.317(0.041) 6
2005 Jun 30 3551.73 18.07 15.251(0.035) 14.984(0.025) 14.210(0.026) 14.216(0.032) 14.314(0.041) 1
2005 Jun 30 3552.07 18.41 15.045(0.032) 14.279(0.022) 14.206(0.032) 14.316(0.041) 3
2005 Jul 1 3553.44 19.78 15.229(0.031) 14.323(0.022) 14.244(0.032) 14.290(0.041) 6
2005 Jul 2 3553.73 20.07 15.513(0.039) 15.193(0.021) 14.308(0.022) 14.242(0.032) 14.270(0.041) 1
2005 Jul 2 3553.83 20.17 15.224(0.022) 14.351(0.022) 14.250(0.032) 14.279(0.041) 7
2005 Jul 2 3554.45 20.79 15.298(0.021) 14.405(0.022) 14.260(0.032) 14.280(0.041) 6
2005 Jul 3 3554.66 21.00 15.308(0.022) 14.369(0.022) 14.280(0.032) 14.263(0.041) 4
2005 Jul 4 3555.77 22.11 15.761(0.038) 15.439(0.025) 14.430(0.026) 14.288(0.031) 14.294(0.041) 1
2005 Jul 6 3557.68 24.02 15.977(0.035) 15.604(0.022) 14.535(0.022) 14.261(0.032) 14.260(0.041) 2
2005 Jul 6 3557.73 24.07 16.008(0.034) 15.621(0.026) 14.506(0.024) 14.302(0.032) 14.217(0.041) 1
2005 Jul 7 3559.48 25.82 15.791(0.022) 14.636(0.022) 14.381(0.032) 14.230(0.041) 6
2005 Jul 8 3559.59 25.93 15.801(0.022) 14.663(0.022) 14.383(0.032) 14.223(0.041) 8
2005 Jul 8 3559.61 25.95 15.811(0.022) 14.645(0.022) 14.401(0.032) 14.201(0.041) 4
2005 Jul 8 3559.70 26.04 16.149(0.044) 15.778(0.022) 14.626(0.021) 14.345(0.032) 14.197(0.041) 1
2005 Jul 8 3559.73 26.07 15.765(0.021) 14.610(0.027) 14.357(0.032) 14.192(0.041) 7
2005 Jul 8 3559.76 26.10 15.799(0.022) 14.662(0.022) 14.391(0.032) 14.304(0.041) 5
2005 Jul 10 3561.73 28.07 16.280(0.035) 15.925(0.022) 14.738(0.024) 14.417(0.032) 14.186(0.041) 1
2005 Jul 10 3562.42 28.76 16.010(0.022) 14.829(0.022) 14.470(0.032) 14.220(0.041) 6
2005 Jul 11 3562.63 28.97 16.071(0.022) 14.813(0.022) 14.497(0.032) 14.203(0.041) 4
2005 Jul 11 3562.72 29.06 16.373(0.035) 16.057(0.022) 14.817(0.022) 14.496(0.032) 5
2005 Jul 11 3563.03 29.37 16.101(0.025) 14.811(0.026) 14.482(0.032) 14.196(0.041) 3
2005 Jul 11 3563.42 29.76 16.081(0.023) 14.904(0.022) 14.497(0.032) 14.245(0.041) 6
2005 Jul 12 3563.70 30.04 16.101(0.025) 14.859(0.022) 14.513(0.032) 14.232(0.041) 7
2005 Jul 12 3563.73 30.07 16.433(0.045) 16.127(0.024) 14.854(0.023) 14.515(0.032) 14.214(0.041) 1
2005 Jul 13 3565.39 31.73 16.256(0.022) 15.004(0.022) 14.632(0.032) 14.311(0.041) 6
2005 Jul 14 3565.71 32.05 16.544(0.071) 16.244(0.025) 14.943(0.022) 14.609(0.032) 14.263(0.041) 1
2005 Jul 17 3569.40 35.74 16.479(0.031) 15.302(0.022) 14.914(0.032) 14.587(0.041) 6
2005 Jul 18 3569.54 35.88 16.483(0.022) 15.244(0.022) 14.902(0.032) 14.536(0.041) 4
2005 Jul 19 3570.70 37.04 16.926(0.141) 16.501(0.033) 15.323(0.027) 14.986(0.035) 14.624(0.041) 1
2005 Jul 19 3570.80 37.14 16.508(0.054) 15.285(0.027) 14.979(0.032) 14.583(0.041) 7
2005 Jul 21 3572.70 39.04 16.818(0.138) 16.632(0.037) 15.368(0.022) 15.052(0.032) 14.665(0.041) 1
2005 Jul 22 3573.60 39.94 16.638(0.026) 15.473(0.022) 15.166(0.032) 14.829(0.041) 4
2005 Jul 23 3574.70 41.04 16.845(0.059) 16.674(0.023) 15.482(0.022) 15.195(0.032) 14.878(0.041) 1
2005 Jul 23 3574.76 41.10 16.690(0.036) 15.480(0.024) 15.161(0.032) 14.865(0.041) 7
2005 Jul 24 3576.40 42.74 16.710(0.022) 15.580(0.022) 15.061(0.041) 6
2005 Jul 25 3576.61 42.95 16.744(0.022) 15.554(0.022) 15.287(0.032) 15.002(0.041) 4
2005 Jul 25 3576.73 43.07 16.945(0.088) 16.735(0.025) 15.574(0.022) 15.292(0.032) 14.997(0.041) 1
2005 Jul 27 3578.69 45.03 16.873(0.086) 16.723(0.022) 15.601(0.022) 15.348(0.032) 15.096(0.041) 1
2005 Jul 28 3579.55 45.89 16.805(0.022) 15.661(0.022) 15.396(0.032) 15.140(0.041) 4
2005 Jul 29 3580.69 47.03 17.141(0.123) 16.789(0.026) 15.649(0.022) 15.415(0.032) 15.169(0.041) 1
2005 Jul 29 3581.00 47.34 16.828(0.055) 15.691(0.022) 15.451(0.032) 15.236(0.065) 3
2005 Jul 31 3582.69 49.03 17.011(0.095) 16.839(0.025) 15.683(0.032) 15.466(0.032) 15.270(0.041) 1
2005 Aug 2 3584.69 51.03 17.014(0.088) 16.841(0.028) 15.775(0.032) 15.550(0.032) 15.373(0.041) 1
2005 Aug 4 3586.69 53.03 17.056(0.084) 16.885(0.033) 15.820(0.032) 15.591(0.032) 15.419(0.041) 1
2005 Aug 6 3588.69 55.03 17.248(0.132) 16.906(0.026) 15.924(0.032) 15.735(0.032) 15.589(0.041) 1
2005 Aug 6 3588.71 55.05 16.905(0.033) 15.886(0.032) 15.684(0.032) 15.606(0.042) 7
2005 Aug 8 3590.69 57.03 17.323(0.094) 16.957(0.027) 15.901(0.032) 15.746(0.032) 15.605(0.041) 1
2005 Aug 10 3592.69 59.03 17.291(0.142) 17.013(0.031) 15.963(0.032) 15.819(0.032) 15.727(0.041) 1
2005 Aug 14 3596.68 63.02 17.070(0.055) 16.140(0.037) 15.910(0.032) 1
2005 Aug 17 3599.68 66.02 17.121(0.059) 16.164(0.032) 16.047(0.032) 16.002(0.041) 1
2005 Aug 18 3601.01 67.35 16.240(0.032) 16.094(0.025) 16.074(0.041) 3
2005 Aug 19 3602.67 69.01 17.115(0.051) 16.259(0.032) 16.150(0.032) 16.201(0.041) 1
2005 Aug 20 3604.01 70.35 17.225(0.038) 16.309(0.032) 16.201(0.027) 16.297(0.041) 3
2005 Aug 21 3605.11 71.35 17.263(0.078) 16.350(0.064) 3
2005 Aug 22 3605.67 72.01 17.270(0.051) 16.310(0.032) 16.219(0.032) 16.295(0.041) 1
2005 Aug 25 3608.67 75.01 17.261(0.051) 16.421(0.032) 16.308(0.032) 16.443(0.041) 1
2005 Aug 28 3611.67 78.01 17.175(0.051) 16.429(0.032) 16.385(0.032) 16.487(0.041) 1
2005 Aug 31 3614.66 81.00 17.309(0.051) 16.573(0.032) 16.489(0.032) 16.575(0.041) 1
2005 Sept 3 3617.66 84.00 17.325(0.051) 16.663(0.034) 16.625(0.032) 16.744(0.041) 1
2005 Sept 4 3618.65 84.99 17.453(0.051) 16.646(0.032) 16.572(0.032) 16.836(0.041) 1
2005 Sept 7 3621.66 88.00 17.545(0.051) 16.706(0.031) 16.739(0.034) 17.061(0.054) 1
2005 Sept 10 3624.65 90.99 17.422(0.064) 16.844(0.039) 16.756(0.032) 17.054(0.047) 1
55
Table 3The - and -corrected Optical Photometry of SN 2005cf.
UT Date JD - 2,450,000 Phase56
31/05/05 3522.24 -11.42 14.724(0.023) 14.689(0.019) 14.825(0.021) 0.015 0.010 0.016
01/06/05 3523.25 -10.41 14.495(0.015) 14.514(0.031) 0.015 0.010
02/06/05 3524.24 -9.42 14.254(0.028) 14.316(0.031) 14.347(0.021) 0.015 0.010 0.016
10/06/05 3532.23 -1.43 13.841(0.039) 13.969(0.023) 14.002(0.023) 0.011 0.006 0.026
12/06/05 3534.23 0.57 14.035(0.044) 14.040(0.036) 13.995(0.015) 0.010 0.004 0.030
13/06/05 3535.22 1.56 13.997(0.013) 14.142(0.014) 14.102(0.034) 0.009 -0.003 0.034
14/06/05 3536.21 2.55 14.076(0.014) 14.154(0.034) 14.093(0.019) 0.008 -0.006 0.038
17/06/05 3539.21 5.55 14.346(0.023) 14.169(0.056) 14.184(0.029) 0.006 -0.010 0.046
29/06/05 3551.16 17.50 15.365(0.025) 13.974(0.064) 14.288(0.019) 0.022 -0.021 0.037
01/07/05 3553.17 19.51 15.339(0.028) 13.943(0.063) 14.196(0.017) 0.025 -0.021 0.032
02/07/05 3554.17 20.51 15.333(0.023) 14.060(0.033) 0.027 -0.022
03/07/05 3555.28 21.62 15.294(0.018) 13.979(0.060) 14.181(0.017) 0.029 -0.023 0.026
04/07/05 3556.17 22.51 15.261(0.023) 14.040(0.017) 14.167(0.021) 0.030 -0.024 0.023
05/07/05 3557.15 23.49 15.174(0.023) 13.984(0.081) 14.101(0.011) 0.033 -0.022 0.019
06/07/05 3558.15 24.49 15.191(0.036) 13.983(0.089) 14.105(0.023) 0.036 -0.021 0.016
08/07/05 3560.16 26.50 14.995(0.026) 14.017(0.018) 14.123(0.021) 0.041 -0.017 0.008
11/07/05 3563.15 29.49 14.846(0.024) 14.087(0.021) 14.219(0.019) 0.041 -0.008 0.005
57
Table 4 Magnitudes of SN 2005cf from PAIRITEL
UT Date JD2,450,000 Phase58 Range(Å) Res.59(Å) Airmass Exposure(s) Inst.60 Observers
31/05/2005 3521.7 12.0 3480–7500 7 1.3 1200 Fast PB
01/06/2005 3522.7 11.0 3480–7500 7 1.3 960 Fast PB
01/06/2005 3522.9 10.8 3300–10400 5–12 1.8 600 Kast MG;DW;BS
02/06/2005 3523.7 10.0 3480–7500 7 1.3 600 Fast PB
02/06/2005 3523.9 9.8 3300–10400 5–12 1.3 300 Kast DR
03/06/2005 3524.7 9.0 3480–7500 7 1.3 900 Fast MC
03/06/2005 3524.9 8.8 3300–10400 5–12 1.4 300 Kast DR
04/06/2005 3525.9 7.8 3300–10400 5–12 1.4 600 Kast DR
05/06/2005 3526.9 6.8 3300–10400 5–12 1.4 600 Kast DR
06/06/2005 3527.9 5.8 3300–10400 5–12 1.4 600 Kast MAM
07/06/2005 3528.7 5.0 3480–7500 7 1.3 900 Fast PB
08/06/2005 3529.7 4.0 3480–7500 7 1.3 900 Fast PB
09/06/2005 3530.7 3.0 3480–7500 7 1.3 900 Fast PB
10/06/2005 3531.8 1.9 3480–7500 7 1.7 900 Fast PB
10/06/2005 3531.8 1.9 3300–10400 5-12 1.4 300 Kast MG;FS
11/06/2005 3532.7 1.0 3300–10400 5–12 1.5 600 Kast FS
11/06/2005 3532.8 0.9 3480–7500 7 1.5 600 Fast MC
12/06/2005 3533.8 0.2 3480–7500 7 2.1 600 Fast MC
13/06/2005 3534.7 1.1 3480–7500 7 1.4 600 Fast PB
14/06/2005 3535.7 2.0 3300–10400 5–12 1.4 600 Kast AF;MG;BS
14/06/2005 3535.8 2.1 3480–7500 7 1.5 600 Fast PB
15/06/2005 3536.7 3.0 3480–7500 7 1.3 600 Fast PB
16/06/2005 3537.6 3.9 3480–7500 7 1.3 780 Fast MC
17/06/2005 3538.7 5.0 3480–7500 7 1.3 660 Fast MC
29/06/2005 3550.8 17.1 3480–7500 7 2.0 900 Fast RH
01/07/2005 3552.7 19.0 3300–10400 5–12 1.4 300 Kast MG;DW
04/07/2005 3555.7 22.0 3480–7500 7 1.4 600 Fast JG
06/07/2005 3557.7 24.0 3480–7500 7 1.4 900 Fast JG
07/07/2005 3558.6 24.9 3480–7500 7 1.3 900 Fast EF
08/07/2005 3559.6 25.9 3480–7500 7 1.3 900 Fast PB
09/07/2005 3560.7 27.0 3480–7500 7 1.5 900 Fast PB
10/07/2005 3561.7 28.0 3480–7500 7 1.4 900 Fast PB
10/07/2005 3561.7 28.0 3300–10400 5–12 1.5 500 Kast AF;FS
11/07/2005 3562.7 29.0 3480–7500 7 1.4 900 Fast MC
12/07/2005 3563.9 30.2 3480–7500 7 1.3 1800 Fast MC
26/07/2005 3577.6 43.9 3480–7500 7 1.4 1800 Fast PB
28/07/2005 3579.6 45.9 3480–7500 7 1.5 1200 Fast PB
03/09/2005 3616.6 82.9 3480–7500 7 2.2 1200 Fast MC
26/04/2006 3853.1 319.4 3250–9250 6 1.5 1200 LRISB AF;RF
16/02/2007 4148.1 614.4 4585–7230 1.3 1.3 6300 DEIMOS AF;JS;RF;RC
6162
Table 5Journal of spectroscopic observations of SN 2005cf
UT Date JD Phase63 F220W F250W F330W
03/06/05 3524.99 -8.67 19.978(070) 16.624(015) 14.675(005)
05/06/05 3527.26 -6.40 19.024(030) 15.638(005) 13.766(004)
07/06/05 3529.36 -4.30 18.557(019) 15.341(005) 13.439(005)
11/06/05 3532.96 -0.70 18.189(038) 14.972(004) 13.272(004)
14/06/05 3535.95 2.28 18.160(051) 15.026(004) 13.395(004)
16/06/05 3537.95 4.29 18.131(027) 15.243(005) 13.719(006)
21/06/05 3542.61 9.02 18.240(009) 15.941(005) 14.424(004)
25/06/05 3547.28 13.62 18.665(011) 16.589(005) 15.051(004)
26/06/05 3547.98 14.32 18.745(007) 16.745(008) 15.259(005)
29/06/05 3551.28 17.68 19.060(013) 17.068(005) 15.677(004)
30/06/05 3551.77 18.11 19.158(009) 17.162(005) 15.797(005)
05/07/05 3557.07 23.41 19.524(023) 17.766(008) 16.369(005)
64
Table 6HST ACS Ultraviolet Photometry of SN 2005cf
UT Date JD Phase65 66 67 Color Correction S Correction
2,450,000 F110W F160W F110W F160W
2005 June 3 3525.08 8.58 14.246(0.030) 14.185(0.025) 0.126 0 0.162 0.120
2005 June 7 3527.15 6.51 13.932(0.029) 13.905(0.023) 0.116 0 0.190 0.110
2005 June 10 3529.81 3.85 13.803(0.029) 13.885(0.023) 0.207 -0.002 0.220 0.095
2005 June 13 3533.14 0.52 13.821(0.029) 13.945(0.023) 0.222 -0.002 0.235 0.078
2005 June 16 3536.74 3.08 14.222(0.030) 14.229(0.025) 0.168 -0.001 0.143 0.056
2005 June 18 3538.87 5.21 14.370(0.030) 14.285(0.025) 0.175 -0.001 0.040 0.047
2005 June 23 3544.01 10.35 15.093(0.032) 14.357(0.027) 0.119 0 0.410 0.195
2005 June 27 3548.08 14.42 15.389(0.032) 14.197(0.026) 0.021 0.002 0.730 0.275
2005 July 1 3552.08 18.42 15.350(0.032) 14.132(0.025) 0.045 0.003 0.710 0.250
2005 July 7 3558.00 24.34 15.271(0.032) 14.063(0.025) 0.042 0.003 0.720 0.210
Table 7HST NICMOS3 NIR Photometry of SN 2005cf
UT Date JD68 Phase69
2005 June 4 3525.55 -8.11 17.79(0.09) 19.69 16.34(0.07) 14.31(0.05) 14.26(0.05) 14.36(0.05) -0.17 -0.02 0.01
2005 June 5 3526.55 -7.11 17.53(0.08) 20.00 15.91(0.06) 13.99(0.05) 14.17(0.09) 14.16(0.05) -0.13 -0.01 0.01
2005 June 6 3527.55 -6.11 17.33(0.08) 19.45(0.31) 15.58(0.06) 13.76(0.05) 13.92(0.06) 14.02(0.04) -0.11 -0.01 0.01
2005 June 8 3530.43 -3.23 16.91(0.07) 18.76(0.31) 15.18(0.05) 13.37(0.06) 13.66(0.06) 13.73(0.05) -0.12 -0.01 0.01
2005 June 9 3530.77 -2.89 16.94(0.06) 19.26(0.26) 15.10(0.05) 13.40(0.06) 13.65(0.07) 13.70(0.05) -0.12 -0.01 0.01
2005 June 10 3531.97 -1.69 16.85(0.06) 18.36(0.16) 15.10(0.05) 13.34(0.06) 13.60(0.07) 13.66(0.05) -0.12 -0.01 0.01
2005 June 11 3533.05 -0.61 16.83(0.06) 18.50(0.16) 15.13(0.05) 13.61(0.06) 0.01
2005 June 16 3538.26 4.60 17.15(0.07) 18.32(0.15) 15.39(0.05) 13.58(0.06) 0.02
2005 June 17 3538.74 5.08 17.07(0.07) 18.31(0.15) 15.44(0.05) 13.63(0.06) 0.02
2005 June 20 3542.15 8.49 17.39(0.07) 18.47(0.15) 15.83(0.06) 13.70(0.06) 0.03
2005 June 22 3543.70 10.04 17.47(0.08) 18.58(0.20) 16.03(0.09) 13.75(0.07) 0.03
2005 June 26 3548.26 14.60 18.06(0.10) 18.62(0.18) 16.63(0.07) 14.82(0.05) 14.65(0.05) 14.09(0.05) -0.21 0 0.04
2005 June 29 3550.51 16.85 18.21(0.11) 18.92(0.24) 16.96(0.09) 15.14(0.05) 14.91(0.05) 14.25(0.05) -0.22 0 0.04
2005 July 12 3564.32 30.66 19.36(0.29) 19.76 18.17(0.16) 16.46(0.08) 16.07(0.06) 14.94(0.05) -0.17 0 0.06
2005 July 23 3575.16 41.50 17.05(0.06) 16.65(0.05) 15.60(0.05) -0.18 0 0.05
2005 July 24 3575.97 42.31 19.77(0.19) 20.29 18.60(0.11)
Table 8Swift UVOT Ultraviolet/Optical Photometry of SN 2005cf.
Band
(Å) 2,450,000 (mag) (mag)
1928 3533.050.50 16.840.05 1.110.06
2246 3537.860.71 18.300.13 0.750.08
2600 3532.350.44 15.100.04 1.440.05
F220W 2228 3537.170.48 18.140.05 1.000.06
F250W 2696 3532.490.42 15.130.04 1.540.05
F330W 3354 3532.300.40 13.310.04 1.910.05
3650 3532.420.30 13.400.03 1.260.04
4450 3533.660.28 13.630.02 1.050.03
5500 3535.540.33 13.550.02 0.620.03
6450 3534.800.26 13.530.03 0.670.03
7870 3532.560.34 13.760.04 0.590.03
12700 3530.540.44 13.780.05 1.450.05
16700 3529.480.42 13.840.04 0.420.05
22200 3530.320.59 13.940.05 0.400.06
Table 9Light-curve parameters of SN 2005cf
Days
-12 2.58 2.00 1.78 1.75 1.61
-11 1.97 1.55 1.45 1.37 1.28
-10 1.48 1.20 1.17 1.05 0.97
-9 1.08 0.91 0.93 0.80 0.70
-8 0.76 0.68 0.72 0.60 0.48
-7 0.51 0.49 0.56 0.44 0.31
-6 0.33 0.35 0.41 0.32 0.18
-5 0.19 0.23 0.30 0.22 0.09
-4 0.09 0.14 0.21 0.14 0.04
-3 0.04 0.08 0.14 0.09 0.01
-2 0.01 0.03 0.08 0.05 0
-1 0 0.01 0.04 0.02 0.01
0 0.02 0 0.02 0.01 0.02
1 0.05 0.01 0 0 0.04
2 0.10 0.03 0 0 0.05
3 0.16 0.06 0.01 0.02 0.08
4 0.22 0.11 0.02 0.04 0.10
5 0.30 0.16 0.04 0.07 0.13
6 0.39 0.23 0.07 0.11 0.16
7 0.48 0.30 0.11 0.16 0.21
8 0.58 0.37 0.15 0.21 0.27
9 0.69 0.46 0.19 0.27 0.33
10 0.80 0.55 0.24 0.34 0.41
11 0.92 0.64 0.29 0.40 0.48
12 1.04 0.73 0.34 0.47 0.54
13 1.17 0.84 0.39 0.53 0.57
14 1.31 0.94 0.45 0.59 0.59
15 1.45 1.05 0.50 0.63 0.59
16 1.59 1.15 0.56 0.66 0.59
17 1.74 1.27 0.61 0.68 0.59
18 1.89 1.38 0.67 0.70 0.57
19 2.02 1.49 0.72 0.72 0.56
20 2.15 1.60 0.78 0.74 0.54
21 2.27 1.71 0.83 0.75 0.52
22 2.38 1.81 0.88 0.76 0.50
23 2.49 1.91 0.93 0.78 0.48
24 2.59 2.00 0.98 0.80 0.47
25 2.68 2.10 1.04 0.82 0.46
26 2.77 2.19 1.09 0.85 0.45
27 2.85 2.27 1.14 0.89 0.45
28 2.92 2.36 1.21 0.93 0.46
29 2.99 2.44 1.29 0.97 0.47
30 3.06 2.51 1.35 1.02 0.50
31 3.12 2.58 1.42 1.08 0.53
34 3.27 2.77 1.60 1.27 0.66
37 3.38 2.92 1.75 1.47 0.86
40 3.46 3.03 1.88 1.64 1.08
43 3.53 3.11 1.99 1.77 1.28
46 3.58 3.16 2.09 1.89 1.40
49 3.65 3.21 2.18 1.98 1.53
52 3.72 3.26 2.26 2.08 1.66
57 3.83 3.34 2.39 2.23 1.88
62 3.94 3.42 2.51 2.39 2.10
65 4.00 3.46 2.58 2.49 2.23
70 4.11 3.54 2.71 2.64 2.45
75 4.22 3.62 2.84 2.80 2.67
80 4.33 3.70 2.98 2.96 2.89
85 4.44 3.78 3.12 3.12 3.10
90 4.55 3.86 3.25 3.28 3.32
Table 10The Template Light Curves of SN 2005cf70

Table 11The Intrinsic color Relation
Color
71 0.09(04) 0.15(03) 0.03
72 1.61(35) 2.60(47) 0.11
73 0.27(01) 0.22(03) 0.06
74 1.03(10) 1.45(14) 0.06
0.25(01) 0.34(05) -0.38(21) 1.98(23) 0.04
75 1.02(01) 0.04
76 0.72(07) 0.46(10) 0.04
77
Method E References
1,2
1,2
3,2
4,2
1
5
5
5
Mean

References. – (1) Phillips et al. (1999); (2) this paper; (3) Wang et al. (2005); (4) Jha et al. (2007); (5) Krisciunas et al. (2004).

Table 12Host-galaxy reddening of SN 2005cf
Parameter Value Source
Photometric parameters
Discovery date 28.26 May 2005 1
Epoch of maximum 2
mag 2
mag 2
mag 2
(true) mag 2
(true) 2
Late-time decline rate mag (100 d) 2
L erg s 2
 d 2
Ni  M 2
Spectroscopic parameters
(Si II 6355) 10,100 km s 2
(S II 5460) 9600 km s 2
(Si II 6355) km s 2
(Si II) 2
Parameters for MCG-01-39-003
Galaxy type S0 pec 3
E 0.097 3
() 32.310.11 2
v 1937 km s 3

References: (1) Hugh & Li 2005; (2) this paper; (3) NASA Extragalactic Database.

Table 13Relevant parameters for SN 2005cf and its host.

Appendix A The - and -corrections

It is always tricky to transform photometric observations from one filter system to another, requiring many response parameters characterizing the instruments. According to the description in Stritzinger et al. (2002), the instrumental response can be simply defined as

(A1)

where is the filter transmission function, is the transparency of the Earth’s atmosphere, and is the detector quantum efficiency. The atmospheric transmission at the sites where it is not directly available was obtained by modifying the standard atmospheric model (Walker 1987) to be consistent with the average broadband absorption coefficients. Here we did not include the mirror reflectivities, dichroic transmission, or dewar window transmissions due to the absence of this information. Various instrumental responses, normalized to the peak transmission, are shown in Figure 2.

To check whether the instrumental response curves match those actually used at the telescopes, we computed the synthetic magnitudes and hence the color terms by convolving the model curves with a large sample of spectrophotometric standard stars from Stritzinger et al. (2005). The resulting synthetic color terms are generally consistent with the values listed in Table 1 of the main text, but small differences are present. The differences are probably due to the mirror reflectivities, dichroic mirror transmission, or other unknown transmissivity of the optical elements. Following the method proposed by Stritzinger et al. (2002), we shifted the wavelength of the model response curves in order to reproduce exactly the measured color terms. The wavelength shifts of different instrumental responses are given in Table A1. They are usually 100 Å, except in the and filters at the CTIO 1.3 m telescope where the required shifts are 128 Å and 377 Å, respectively.

Telescope
KAIT 0.8 m 29 blue 20 blue 9 red 38 blue 29 blue
CfA 1.2 m 29 blue 58 red 9 red 0 0
CTIO 1.3 m 70 blue 58 blue 128 blue 377 blue
CTIO 0.9 m 6 blue 0 0 46 blue 41 red
Palomar 1.5 m 0 17 red 15 red 107 blue
Lick 1.0 m 38 blue 38 red 46 red 15 blue 58 red
Liverpool 2.0 m 35 blue 9 red 0 29 red
Table 14Wavelength Shifts to Instrumental Response Curves78

With proper model response curves and better spectral coverage for SN 2005cf, we are able to compute the -corrections using

(A2)

where is the -band SN magnitude synthesized with the Bessell function, and and are (respectively) the -band and -band magnitudes synthesized with the instrumental response function. The color term is , and is the zeropoint, which can be determined from the spectrophotomeric standards with a precision close to 0.01 mag. However, since the spectra of SN 2005cf taken 1–3 months after -band maximum did not have adequate wavelength coverage and were sparsely sampled, we also used the spectra of SN 2003du (Stanishev et al. 2007) to compute the -corrections during that phase.

In order to estimate the corresponding -corrections at any epochs without photometry, a polynomial function was used to fit the data points shown in Figure 3. The resulting -corrections are listed in Table A2 (columns 4–8).

Owing to a redshift effect on the spectral energy distribution, we further computed the -corrections for SN 2005cf in the optical bands. The -corrections, based on the response curves of the Bessell filter band and the observed spectra of SNe 2005cf and 2003du, are listed in Table A2 (columns 9–13). Except in the band, the -corrections are generally small, 0.02–0.03 mag around maximum brightness, and they depend on the supernova phase.

UT Date JD Phase79 Inst.80
2005 May 31 3521.75 -11.91 0.038 -0.042 -0.012 -0.022 0.015 -0.087 0.004 0.014 0.016 0.017 2
2005 May 31 3521.77 -11.89 0.075 -0.036 0.009 0 -0.020 -0.087 0.004 0.014 0.016 0.017 1
2005 Jun 1 3522.74 -10.92 0.032 -0.043 -0.014 -0.025 0.018 -0.073 0.006 0.013 0.016 0.018 2
2005 Jun 1 3522.87 -10.79 0.071 -0.034 0.005 1E-3 -0.015 -0.071 0.007 0.013 0.016 0.019 1
2005 Jun 1 3523.15 -10.51 -0.069 0.007 0.013 0.016 0.019 3
2005 Jun 2 3523.77 -9.89 0.021 -0.040 -0.015 -0.027 0.017 -0.060 0.008 0.013 0.016 0.019 2
2005 Jun 2 3523.87 -9.79 0.063 -0.033 0.003 0.002 -0.011 -0.059 0.009 0.013 0.016 0.019 1
2005 Jun 2 3524.13 -9.53 -0.057 0.009 0.013 0.016 0.019 3
2005 Jun 3 3524.63 -9.03 -0.033 -0.028 0.025 0.037 0.010 0.013 0.016 0.020 4
2005 Jun 3 3524.68 -8.98 -0.037 -0.015 -0.029 0.017 0.010 0.013 0.016 0.020 2
2005 Jun 3 3524.79 -8.87 -0.034 0.002 0.002 0.004 0.010 0.013 0.016 0.020 5
2005 Jun 3 3524.85 -8.81 0.047 -0.031 0 0.003 -0.010 -0.049 0.010 0.013 0.016 0.020 1
2005 Jun 3 3525.42 -8.24 -0.024 -0.013 0.026 0.027 0.011 0.013 0.016 0.020 6
2005 Jun 4 3525.69 -7.97 0.007 -0.035 -0.016 -0.03 0.018 -0.043 0.011 0.012 0.016 0.020 2
2005 Jun 4 3525.76 -7.90 -0.032 -0.003 0.006 -0.003 0.011 0.012 0.016 0.020 5
2005 Jun 4 3525.87 -7.79 -0.031 -0.009 0.007 0.026 0.011 0.012 0.016 0.020 7
2005 Jun 5 3526.68 -6.98 -0.032 -0.017 -0.027 0.020 0.012 0.012 0.017 0.019 2
2005 Jun 5 3526.75 -6.91 0.042 -0.031 -0.004 -0.036 0.012 0.012 5
2005 Jun 5 3527.44 -6.22 -0.023 -0.015 0.032 0.010 0.012 0.012 0.018 0.019 6
2005 Jun 6 3527.64 -6.02 -0.028 -0.021 0.020 0.018 0.012 0.012 0.018 0.019 4
2005 Jun 6 3527.69 -5.97 0.003 -0.031 -0.018 -0.026 0.012 -0.032 0.012 0.012 0.018 0.019 2
2005 Jun 6 3527.85 -5.81 0.018 -0.028 -0.004 0.007 -0.002 -0.031 0.012 0.012 0.018 0.018 1
2005 Jun 6 3528.43 -5.23 -0.023 -0.016 0.036 1E-3 0.012 0.012 0.018 0.018 6
2005 Jun 7 3528.75 -4.91 -0.029 -0.008 0.012 0.013 0.012 0.011 0.019 0.018 7
2005 Jun 7 3528.84 -4.82 0.012 -0.028 -0.004 0.009 -0.002 -0.028 0.012 0.011 0.019 0.017 1
2005 Jun 8 3529.43 -4.23 -0.022 -0.016 0.038 -0.016 0.012 0.011 0.019 0.017 6
2005 Jun 8 3529.71 -3.95 0.022 -0.017 0.007 0.003 -0.025 -0.026 0.012 0.011 0.020 0.016 8
2005 Jun 8 3530.42 -3.24 -0.021 -0.017 0.041 -0.021 0.012 0.011 0.020 0.015 6
2005 Jun 8 3530.59 -3.07 -0.028 -0.020 0.017 -0.012 0.012 0.011 0.021 0.015 4
2005 Jun 9 3530.68 -2.98 -0.011 -0.03 -0.019 -0.022 -0.024 -0.025 0.012 0.011 0.021 0.015 2
2005 Jun 10 3531.67 -1.99 -0.012 -0.03 -0.019 -0.021 -0.04 -0.024 0.011 0.010 0.022 0.013 2
2005 Jun 10 3531.79 -1.87 -0.028 -0.007 0.017 0 0.011 0.010 0.022 0.013 7
2005 Jun 10 3531.83 -1.83 -0.005 -0.027 -0.004 0.014 -0.006 -0.024 0.011 0.010 0.022 0.013 1
2005 Jun 10 3532.42 -1.24 -0.020 -0.017 0.045 -0.042 0.011 0.010 0.022 0.012 6
2005 Jun 11 3532.87 -0.79 0 -0.027 -0.004 0.016 -0.007 -0.025 0.011 0.010 0.023 0.011 1
2005 Jun 11 3533.42 -0.24 -0.019 -0.017 0.054 -0.050 0.010 0.010 0.024 0.010 6
2005 Jun 12 3533.66 0.00 -0.028 -0.018 0.011 -0.044 0.010 0.010 0.024 0.009 4
2005 Jun 12 3533.72 0.06 -0.028 -0.007 0.019 -0.008 0.010 0.010 0.024 0.009 7
2005 Jun 12 3533.84 0.18 0 -0.027 -0.004 0.016 -0.007 -0.025 0.010 0.010 0.024 0.009 1
2005 Jun 13 3534.73 1.07 -0.011 -0.031 -0.020 -0.006 -0.08 -0.026 0.009 0.009 0.025 0.007 2
2005 Jun 13 3534.84 1.18 0.005 -0.027 -0.004 0.020 -0.010 -0.027 0.009 0.009 0.025 0.007 1
2005 Jun 13 3535.43 1.77 -0.018 -0.017 0.067 -0.078 0.009 0.009 0.025 0.006 6
2005 Jun 14 3535.72 2.06 -0.027 -0.008 0.022 -0.015 0.009 0.009 0.026 0.005 7
2005 Jun 14 3535.74 2.08 -0.009 -0.032 -0.020 0.005 -0.090 -0.028 0.009 0.009 0.026 0.005 2
2005 Jun 14 3535.83 2.17 0.015 -0.027 -0.004 0.024 -0.028 0.008 0.009 0.026 1
2005 Jun 14 3536.44 2.78 -0.018 -0.017 0.07 -0.089 0.008 0.008 0.026 0.004 6
2005 Jun 15 3536.70 3.04 -0.004 -0.032 -0.020 0.007 -0.103 -0.029 0.008 0.008 0.026 0.003 2
2005 Jun 15 3536.83 3.17 0.017 -0.027 -0.004 0.024 -0.012 -0.030 0.008 0.008 0.027 0.003 1
2005 Jun 15 3537.47 3.81 -0.017 -0.016 0.071 -0.101 0.007 0.008 0.027 0.002 6
2005 Jun 16 3537.82 4.16 -0.004 0.025 -0.013 -0.031 0.007 0.008 0.027 1E-3 1
2005 Jun 17 3538.68 5.02 -0.025 -0.017 0.019 -0.085 0.006 0.007 0.028 -1E-3 4
2005 Jun 21 3542.61 8.95 -0.020 -0.015 0.024 -0.104 0.002 0.005 0.028 -0.007 4
2005 Jun 21 3542.72 9.06 0.035 -0.015 -0.004 0.021 -0.016 -0.040 0.002 0.005 0.028 -0.007 1
2005 Jun 21 3542.76 9.10 -0.024 -0.013 0.022 -0.023 0.002 0.005 0.028 -0.007 7
2005 Jun 21 3543.06 9.40 -0.040 0.002 0.005 0.028 -0.007 3
2005 Jun 22 3543.68 10.02 0.016 -0.024 -0.018 0.015 -0.160 -0.041 1E-3 0.004 0.027 -0.008 2
2005 Jun 22 3543.82 10.16 0.040 -0.013 -0.004 0.021 -0.018 -0.042 1E-3 0.004 0.027 -0.008 1
2005 Jun 23 3544.77 11.11 -0.024 -0.014 0.023 -0.020 0 0.003 0.027 -0.009 7
2005 Jun 23 3544.80 11.14 0.045 -0.011 -0.004 0.018 -0.019 -0.043 0 0.003 0.027 -0.009 1
2005 Jun 24 3545.82 12.16 0.050 -0.010 -0.004 0.016 -0.020 -0.044 -1E-3 0.003 0.026 -0.009 1
2005 Jun 25 3546.75 13.09 0.058 -0.009 -0.004 0.015 -0.020 -0.045 -0.002 0.002 0.024 -0.009 1
2005 Jun 26 3547.67 14.01 -0.014 -0.012 0.026 -0.108 -0.003 1E-3 0.023 -0.009 4
2005 Jun 26 3547.82 14.16 0.062 -0.009 -0.004 0.015 -0.019 -0.046 -0.003 1E-3 0.023 -0.009 1
2005 Jun 27 3548.66 15.00 0.029 -0.023 -0.016 0.015 -0.194 -0.046 -0.004 0 0.022 -0.009 2
2005 Jun 27 3548.79 15.13 0.064 -0.009 -0.005 0.014 -0.016 -0.047 -0.004 0 0.021 -0.009 1
2005 Jun 28 3549.71 16.05 0.028 -0.026 -0.016 0.012 -0.196 -0.047 -0.005 -1E-3 0.020 -0.008 2
2005 Jun 28 3549.74 16.08 -0.026 -0.013 0.021 -0.007 -0.005 -1E-3 0.019 -0.008 7
2005 Jun 28 3549.79 16.13 0.067 -0.011 -0.005 0.013 -0.016 -0.047 -0.005 -1E-3 0.019 -0.008 1
2005 Jun 29 3550.66 17.00 0.031 -0.027 -0.015 0.010 -0.196 -0.048 -0.006 -1E-3 0.017 -0.008 2
2005 Jun 29 3550.67 17.01 -0.012 -0.011 0.043 -0.104 -0.006 -1E-3 0.017 -0.008 4
2005 Jun 29 3550.79 17.13 0.068 -0.012 -0.005 0.012 -0.015 -0.048 -0.006 -0.002 0.017 -0.008 1
2005 Jun 29 3551.49 17.83 -0.015 0 0.044 -0.172 -0.007 -0.002 0.015 -0.008 6
2005 Jun 30 3551.73 18.07 0.069 -0.011 -0.005 0.013 -0.014 -0.048 -0.007 -0.002 0.015 -0.007 1
2005 Jun 30 3552.07 18.41 -0.007 -0.003 0.015 -0.007 3
2005 Jul 1 3553.44 19.78 -0.016 0.0015 0.053 -0.163 -0.008 -0.004 0.015 -0.007 6
2005 Jul 2 3553.73 20.07 0.072 -0.010 -0.005 0.013 -0.012 -0.048 -0.009 -0.005 0.015 -0.006 1
2005 Jul 2 3553.83 20.17 -0.032 -0.010 0.018 0.006 -0.009 -0.005 0.015 -0.006 7
2005 Jul 2 3554.45 20.79 -0.017 0.003 0.057 -0.157 -0.009 -0.005 0.016 -0.006 6
2005 Jul 3 3554.66 21.00 -0.012 -0.006 0.043 -0.091 -0.010 -0.006 0.016 -0.006 4
2005 Jul 4 3555.77 22.11 0.075 -0.013 -0.003 0.012 -0.010 -0.049 -0.010 -0.007 0.016 -0.005 1
2005 Jul 6 3557.68 24.02 0.033 -0.04 -0.011 0.020 -0.153 -0.049 -0.012 -0.009 0.016 -0.005 2
2005 Jul 6 3557.73 24.07 0.077 -0.016 -0.003 0.012 -0.008 -0.049 -0.012 -0.009 0.016 -0.004 1
2005 Jul 7 3559.48 25.82 -0.020 0.008 0.08 -0.126 -0.013 -0.012 0.017 -0.004 6
2005 Jul 8 3559.59 25.93 0.035 -0.016 0.006 -0.002 -0.013 -0.012 0.017 -0.004 8
2005 Jul 8 3559.61 25.95 -0.022 0.003 0.023 -0.074 -0.013 -0.012 0.017 -0.003 4
2005 Jul 8 3559.70 26.04 0.073 -0.025 1E-3 0.012 -0.006 -0.049 -0.013 -0.012 0.017 -0.003 1
2005 Jul 8 3559.73 26.07 -0.046 -0.002 0.011 0.019 -0.013 -0.012 0.017 -0.003 7
2005 Jul 8 3559.76 26.10 -0.046 0.010 0.023 0.045 -0.013 -0.012 0.017 -0.003 5
2005 Jul 10 3561.73 28.07 0.067 -0.026 0.004 0.011 -0.003 -0.049 -0.013 -0.015 0.017 -0.002 1
2005 Jul 10 3562.42 28.76 -0.023 0.010 0.081 -0.118 -0.013 -0.016 0.017 -0.002 6
2005 Jul 11 3562.63 28.97 -0.023 0.004 0.010 -0.063 -0.013 -0.017 0.017 -0.002 4
2005 Jul 11 3562.72 29.06 0.078 -0.048 0.009 0.019 -0.05 -0.013 -0.017 0.017 5
2005 Jul 11 3563.03 29.37 -0.013 -0.017 0.017 -0.002 3
2005 Jul 11 3563.42 29.76 -0.023 0.010 0.08 -0.116 -0.013 -0.018 0.018 -1E-3 6
2005 Jul 12 3563.70 30.04 -0.055 0.003 0.009 0.022 -0.013 -0.018 0.018 -1E-3 7
2005 Jul 12 3563.73 30.07 0.063 -0.024 0.004 0.011 -1E-3 -0.050 -0.013 -0.018 0.018 -1E-3 1
2005 Jul 13 3565.39 31.73 -0.025 0.009 0.079 -0.1 -0.013 -0.021 0.018 0 6
2005 Jul 14 3565.71 32.05 0.058 -0.026 1E-3 0.010 1E-3 -0.051 -0.013 -0.022 0.018 0 1
2005 Jul 17 3569.40 35.74 -0.027 0.006 0.077 -0.089 -0.013 -0.020 0.019 0.002 6
2005 Jul 18 3569.54 35.88 -0.027 0.003 0 -0.043 -0.013 -0.020 0.019 0.002 4
2005 Jul 19 3570.70 37.04 0.047 -0.025 0.003 0.011 0.004 -0.050 -0.013 -0.019 0.019 0.003 1
2005 Jul 19 3570.80 37.14 -0.058 0.003 0.009 0.021 -0.013 -0.019 0.019 0.003 7
2005 Jul 21 3572.70 39.04 0.046 -0.026 0.003 0.012 0.005 -0.052 -0.013 -0.019 0.020 0.004 1
2005 Jul 22 3573.60 39.94 -0.029 0.002 -0.005 -0.036 -0.013 -0.018 0.020 0.005 4
2005 Jul 23 3574.70 41.04 0.044 -0.026 0.004 0.012 0.005 -0.051 -0.013 -0.018 0.020 0.006 1
2005 Jul 23 3574.76 41.10 -0.058 0.002 0.010 0.025 -0.013 -0.018 0.020 0.006 7
2005 Jul 24 3576.40 42.74 -0.027 0.006 -0.077 -0.013 -0.017 0.007 6
2005 Jul 25 3576.61 42.95 -0.029 1E-3 -0.008 -0.032 -0.013 -0.017 0.021 0.007 4
2005 Jul 25 3576.73 43.07 0.044 -0.027 0.004 0.013 0.005 -0.050 -0.013 -0.017 0.021 0.007 1
2005 Jul 27 3578.69 45.03 0.045 -0.028 0.005 0.015 0.007 -0.050 -0.013 -0.016 0.021 0.008 1
2005 Jul 28 3579.55 45.89 -0.031 0 -0.004 -0.029 -0.013 -0.016 0.021 0.009 4
2005 Jul 29 3580.69 47.03 0.046 -0.029 0.004 0.017 0.007 -0.049 -0.013 -0.015 0.021 0.010 1
2005 Jul 29 3581.00 47.34 -0.013 -0.015 0.021 0.010 3
2005 Jul 31 3582.69 49.03 0.048 -0.027 0.003 0.017 0.006 -0.049 -0.013 -0.015 0.021 0.011 1
2005 Aug 2 3584.69 51.03 0.049 -0.025 0.002 0.016 0.007 -0.048 -0.013 -0.014 0.021 0.013 1
2005 Aug 4 3586.69 53.03 0.05 -0.023 0.002 0.016 0.007 -0.048 -0.013 -0.013 0.021 0.014 1
2005 Aug 6 3588.69 55.03 0.051 -0.021 0 0.017 0.007 -0.047 -0.013 -0.012 0.021 0.016 1
2005 Aug 6 3588.71 55.05 -0.046 -0.002 0.018 0.071 -0.013 -0.012 0.021 0.016 7
2005 Aug 8 3590.69 57.03 0.05 -0.019 0 0.017 0.006 -0.047 -0.013 -0.011 0.021 0.017 1
2005 Aug 10 3592.69 59.03 0.05 -0.017 -1E-3 0.016 0.006 -0.046 -0.013 -0.011 0.021 0.019 1
2005 Aug 14 3596.68 63.02 -0.013 -0.002 0.016 -0.014 -0.009 0.020 1
2005 Aug 17 3599.68 66.02 -0.008 -0.002 0.017 0.006 -0.014 -0.008 0.019 0.025 1
2005 Aug 18 3601.01 67.35 -0.014 -0.008 0.019 0.026 3
2005 Aug 19 3602.67 69.01 -0.005 -0.003 0.016 0.006 -0.014 -0.007 0.018 0.027 1
2005 Aug 20 3604.01 70.35 -0.014 -0.007 0.018 0.027 3
2005 Aug 21 3605.11 71.35 -0.014 -0.006 3
2005 Aug 22 3605.67 72.01 -0.002 -0.004 0.017 0.006 -0.014 -0.005 0.017 0.03 1
2005 Aug 25 3608.67 75.01 0.003 -0.003 0.016 0.006 -0.014 -0.004 0.015 0.033 1
2005 Aug 28 3611.67 78.01 0.007 -0.003 0.016 0.006 -0.014 -0.003 0.013 0.036 1
2005 Aug 31 3614.66 81.00 0.011 -0.003 0.016 0.006 -0.014 -0.002 0.011 0.039 1
2005 Sept 3 3617.66 84.00 0.015 -0.003 0.016 0.007 -0.014 -1E-3 0.008 0.042 1
2005 Sept 4 3618.65 84.99 0.018 -0.003 0.015 0.008 -0.014 0 0.007 0.043 1
2005 Sept 7 3621.66 88.00 0.022 -1E-3 0.012 0.009 -0.014 1E-3 0.005 0.046 1
2005 Sept 10 3624.65 90.99 0.026 0 0.010 0.010 -0.014 0.002 0.002 0.049 1
Table 15The - and -corrections added to the magnitudes of SN 2005cf.

Footnotes

  1. affiliation: Department of Astronomy, University of California, Berkeley, CA 94720-3411; wangxf@astro.berkeley.edu .
  2. affiliation: Physics Department and Tsinghua Center for Astrophysics (THCA), Tsinghua University, Beijing, 100084, China; wang_xf@mail.tsinghua.edu.cn .
  3. affiliation: Department of Astronomy, University of California, Berkeley, CA 94720-3411; wangxf@astro.berkeley.edu .
  4. affiliation: Department of Astronomy, University of California, Berkeley, CA 94720-3411; wangxf@astro.berkeley.edu .
  5. affiliation: Department of Astronomy, University of California, Berkeley, CA 94720-3411; wangxf@astro.berkeley.edu .
  6. affiliation: Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA, 02138.
  7. affiliation: Clay Fellow.
  8. affiliation: Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA, 02138.
  9. affiliation: Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA, 02138.
  10. affiliation: Department of Astronomy, University of California, Berkeley, CA 94720-3411; wangxf@astro.berkeley.edu .
  11. affiliation: Miller Fellow.
  12. affiliation: Department of Astronomy, University of California, Berkeley, CA 94720-3411; wangxf@astro.berkeley.edu .
  13. affiliation: Pennsylvania State University, Department of Astronomy & Astrophysics, University Park, PA 16802.
  14. affiliation: Astrophysics Research Institute, Liverpool John Moores University, Tweleve Quays House, Egerton Wharf, Birkenhead CH41 1LD, UK.
  15. affiliation: Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA, 02138.
  16. affiliation: Benoziyo Center for Astrophysics, Weizmann Institute of Science, 76100 Rhovot, Israel.
  17. affiliation: Department of Astronomy, University of California, Berkeley, CA 94720-3411; wangxf@astro.berkeley.edu .
  18. affiliation: Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA, 02138.
  19. affiliation: Department of Physics, Texas A&M University, College Station, Texas, 77843.
  20. affiliation: Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721.
  21. affiliation: Department of Physics, Texas A&M University, College Station, Texas, 77843.
  22. affiliation: Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA, 02138.
  23. affiliation: Department of Physics, University of Pittsburgh, 100 Allen Hall, Pittsburgh, PA 15260.
  24. affiliation: Department of Astronomy, University of California, Berkeley, CA 94720-3411; wangxf@astro.berkeley.edu .
  25. affiliation: Space Radiation Laboratory, MS 220-47, California Institute of Technology, Pasadena, CA 91125
  26. affiliation: Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA, 02138.
  27. affiliation: Pennsylvania State University, Department of Astronomy & Astrophysics, University Park, PA 16802.
  28. affiliation: CASS 0424, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0424.
  29. affiliation: Physics Department and Tsinghua Center for Astrophysics (THCA), Tsinghua University, Beijing, 100084, China; wang_xf@mail.tsinghua.edu.cn .
  30. affiliation: Physics Department and Tsinghua Center for Astrophysics (THCA), Tsinghua University, Beijing, 100084, China; wang_xf@mail.tsinghua.edu.cn .
  31. affiliation: Department of Physics and Astronomy, University of California, Los Angeles, CA 90095-1547.
  32. affiliation: Department of Physics and Astronomy, University of California, Los Angeles, CA 90095-1547.
  33. affiliation: Department of Physics and Astronomy, University of California, Los Angeles, CA 90095-1547.
  34. affiliation: Department of Astronomy, University of California, Berkeley, CA 94720-3411; wangxf@astro.berkeley.edu .
  35. affiliation: Physics Department and Tsinghua Center for Astrophysics (THCA), Tsinghua University, Beijing, 100084, China; wang_xf@mail.tsinghua.edu.cn .
  36. affiliation: Department of Astronomy, University of California, Berkeley, CA 94720-3411; wangxf@astro.berkeley.edu .
  37. affiliation: Department of Astronomy, University of California, Berkeley, CA 94720-3411; wangxf@astro.berkeley.edu .
  38. affiliation: Department of Astronomy, University of California, Berkeley, CA 94720-3411; wangxf@astro.berkeley.edu .
  39. affiliation: CPPM/CNRS Centre de Physique des Particules de Marseille & LAM/CNRS Laboratoire d’Astrophysique de Marseille Universite de la Mediterranee, France.
  40. affiliation: Department of Astronomy, University of California, Berkeley, CA 94720-3411; wangxf@astro.berkeley.edu .
  41. affiliation: Physics Department and Tsinghua Center for Astrophysics (THCA), Tsinghua University, Beijing, 100084, China; wang_xf@mail.tsinghua.edu.cn .
  42. affiliationtext: Department of Astronomy & Astrophysics, 525 Davey Laboratory, Pennsyvania State University University park, PA 16802
  43. IRAF, the Image Reduction and Analysis Facility, is distributed by the National Optical Astronomy Observatory, which is operated by the Association of Universities for Research in Astronomy (AURA), Inc. under cooperative agreement with the National Science Foundation (NSF).
  44. http://www.stsci.edu/hst/nicmos/performance/photometry/
  45. http://kurucz.harvard.edu/
  46. The true for SN 2005cf is mag, taking into account the reddening effect on the light-curve shape (Phillips et al. 1999).
  47. Measurements of the late-time decline rate in the band are usually difficult due to the lack of reliable photometry at this phase. High-quality data are needed to test whether the -band data follow the same trend as shown in .
  48. http://www.stsci.edu/hst/acs/documents/handbooks/cycle17
  49. SNe 1992A, 1992al, 1992bc, 1992bl, 1992bo, 1993H, 1993O, 1994D, 1994S, 1996X, 1998aq, 1998bp, 1998de, 1999by, 1999ej, 2000ca, 2000dk, 2000dr, 2001ba, 2002dl, 2002ha, 2002fk, 2003gs, 2003hv, 2003du, 2004at, 2005el, and 2005ki.
  50. footnotetext: Note: Uncertainties, in units of 0.001 mag, are .
  51. footnotetext: Note: Uncertainties, in units of 0.001 mag, are .
  52. See Fig. 1 for a chart of SN 2005cf and the comparison stars.
  53. Relative to the epoch of -band maximum (JD = 2,453,533.66).
  54. 1 = KAIT 0.76 m; 2 = FLWO 1.2 m; 3 = TNT 0.8 m; 4 = CTIO 1.3 m; 5 = Lick 1.0 m; 6 = Liverpool 2.0 m; 7 = Palomar 1.5 m; 8 = CTIO 0.9 m
  55. footnotetext: Note: Uncertainties, in units of 0.001 mag, are .
  56. Relative to the epoch of -band maximum (JD = 2,453,533.66).
  57. footnotetext: Note: The corrections listed in columns (7)-(9) were added to the magnitudes.
  58. Relative to the maximum (JD=2,453,533.66).
  59. Approximate spectral resolution.
  60. footnotemark:
  61. footnotetext: Fast = FLWO 1.5 m FAST;Kast= Lick Shane 3 m KAST; LIRSB = Keck I 10 m LRISBLUE; DEIMOS = Keck II 10 m DEIMOS.
  62. footnotetext: AF = Alex Filippenko; RH = Robert Hutchins; EF = Emilio Falco; JG = Joseph Gallagher; PB = Perry Berlind; MC = Mike Calkins; MG = Mohan Ganeshalingam; DW = Diane Wong; BS = Brandont Swift; DR = David Reitzel; JS = Jeffrey Silverman; MAM = Matthew. A. Malkan; FS = Frank Serduke; RC = Ryan Chronock; RF = Ryan Floey
  63. Relative to the epoch of -band maximum (JD = 2,453,533.66)
  64. footnotetext: Note: Uncertainties, in units of 0.001 mag, are .
  65. Relative to the epoch of -band maximum (JD = 2,453,533.66)
  66. The - and -band magnitudes were converted, respectively, from the F110W- and F160W-band magnitudes using the color- and S-corrections listed in columns 6–9.
  67. The - and -band magnitudes were converted, respectively, from the F110W- and F160W-band magnitudes using the color- and S-corrections listed in columns 6–9.
  68. Julian Date 2,450,000
  69. Relative to the epoch of -band maximum (JD = 2,453,533.66).
  70. All of the light curves have been normalized to the -band maximum epoch and their peak values listed in Table 9.
  71. The correlation holds for SNe Ia with .
  72. The correlation applies to SNe Ia with .
  73. The correlation holds for SNe Ia with .
  74. The correlation applies to SNe Ia with .
  75. The correlation holds for SNe Ia with .
  76. The correlation applies to SNe Ia with .
  77. footnotetext: .
  78. All values are measured in Angstrom units.
  79. Relative to the epoch of -band maximum (JD = 2,453,533.66).
  80. 1 = KAIT 0.76 m; 2 = FLWO 1.2 m; 3 = TNT 0.8 m; 4 = CTIO 1.3 m; 5 = Lick 1.0 m; 6 = Liverpool 2.0 m; 7 = Palomar 1.5 m; 8 = CTIO 0.9 m

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