M31 RR Lyraes

RR Lyrae Variables in Two Fields in the Spheroid of M311

Abstract

We present Hubble Space Telescope observations taken with the Advanced Camera for Surveys Wide Field Channel of two fields near M32 - between four and six kpc from the center of M31. The data cover a time baseline sufficient for the identification and characterization of 681 RR Lyrae variables of which 555 are ab-type and 126 are c-type. The mean magnitude of these stars is where the uncertainty combines both the random and systematic errors. The location of the stars in the Bailey Diagram and the ratio of c-type RR Lyraes to all types are both closer to RR Lyraes in Oosterhoff type I globular clusters in the Milky Way as compared with Oosterhoff II clusters. The mean periods of the ab-type and c-type RR Lyraes are and , respectively, where the uncertainties in each case represent the standard error of the mean. When the periods and amplitudes of the ab-type RR Lyraes in our sample are interpreted in terms of metallicity, we find the metallicity distribution function to be indistinguishable from a Gaussian with a peak at [Fe/H]=, where the quoted uncertainty is the standard error of the mean. Using a relation between RR Lyrae luminosity and metallicity along with a reddening of , we find a distance modulus of for M31. We examine the radial metallicity gradient in the environs of M31 using published values for the bulge and halo of M31 as well as the abundances of its dwarf spheroidal companions and globular clusters. In this context, we conclude that the RR Lyraes in our two fields are more likely to be halo objects rather than associated with the bulge or disk of M31, in spite of the fact that they are located at 4-6 kpc in projected distance from the center.

stars: variables: other – galaxies: stellar content – galaxies: spiral – galaxies: individual (M31)
3

1 Introduction

Pulsating variable stars such as RR Lyraes are powerful probes useful for investigating the properties of stellar populations. The mere presence of RR Lyraes among a population of stars suggests an ancient origin since ages older than 10 Gyr are required to produce RR Lyrae variables. Their periods and amplitudes are a reflection of the metal abundance of the population. Along with their incredible usefulness, RR Lyraes are also relatively straightforward to identify and characterize. This is because of their short periods and the distinct light curve shapes of the ab-types, which pulsate in the fundamental mode and exhibit a relatively rapid rise to maximum and a gradual decline to minimum. This is in contrast to the c-type RR Lyraes which pulsate in the first harmonic and show light curves that are more akin to sine curves. In spite of the great potential RR Lyraes hold as astrophysical tools, they have not been widely studied in our nearest large neighbor galaxy, Andromeda.

One of the first studies attempting to identify RR Lyraes in M31 was that of Pritchet & van den Bergh (1987). They used the Canada-France-Hawaii 3.6m telescope to observe a field at a distance of 9 kpc from the center of M31 along the minor axis partially overlapping the field observed by Mould & Kristian (1986). They identified 30 RR Lyrae candidates and were able to estimate periods for 28 of them. These ab-type variables have a mean period of =0.548 days. The photometric errors in their data prevented them from identifying the lower-amplitude c-type RR Lyraes.

The RR Lyrae variables in M31 globular clusters have been investigated by Clementini et al. (2001, cf. Contreras et al. 2008). They used the Wide Field Planetary Camera 2 (WFPC2) onboard the Hubble Space Telescope (HST) to make the first tentative detection of RR Lyraes in G11, G33, G64, and G322, finding two, four, 11, and eight variables, respectively. Detection and characterization of these stars in globular clusters is more challenging than in the M31 field because of the increased crowding.

Returning to the work on field RR Lyraes, Dolphin et al. (2004) observed the same field as Pritchet & van den Bergh (1987) using the WIYN 3.5m on Kitt Peak. They found 24 RR Lyrae stars with a completeness fraction of 24%, suggesting that their 100 square arcmin field could contain 100 RR Lyraes resulting in a density of one RR Lyrae per square arcmin. This is much less than the value of 17 per square arcmin found by Pritchet & van den Bergh (1987). They also noted for the first time that the mean metallicity of the M31 RR Lyraes seemed to be significantly lower than that of the M31 halo. The work of Durrell et al. (2001) had reported a peak value of –0.8 for the M31 halo. Dolphin et al. (2004) were not able to reconcile this abundance value with the distance implied by the mean magnitude of their RR Lyrae sample.

The first definitive work on the RR Lyraes of M31 was published by Brown et al. (2004, hereafter B2004) and made use of 84 hours of imaging time (250 exposures over 41 days) with the Advanced Camera for Surveys onboard HST. Their field was located along the minor axis of M31 approximately 11 kpc from its center. Their analysis revealed a complete sample of RR Lyrae stars consisting of 29 ab-type variables and 25 c-type. The periods of these stars suggest a mean metallicity of -1.6 for the old population in the Andromeda halo. This is qualitatively consistent with the assertions of Dolphin et al. (2004) regarding the metal abundance of the M31 halo - that it is lower than the value suggested by the work of Durrell et al. (2001). More recent work has shown that the M31 halo extends from 30 to 165 kpc (Guhathakurta et al. 2005; Irwin et al. 2005) and has a metallicity that is actually closer to that of the Milky Way halo (Kalirai et al. 2006; Koch et al. 2008).

There is one more paper of note related to this topic and that is the work of Alonso-García et al. (2004). They used the Wide Field Planetary Camera 2 onboard HST to image a field 3.5 arcmin to the east of M32 and compared it with a control field that samples the M31 field stars well away from M32. They identify variable stars that they claim are RR Lyraes belonging to M32 therefore suggesting that M32 possesses a population that is older than 10 Gyr. They were not able to classify the RR Lyraes or derive periods and amplitudes for them so their results are not directly comparable to ours.

This review of the literature reveals a significant deficiency in the spatial coverage of RR Lyrae studies in the vicinity of M31. Given the great astrophysical utility of RR Lyrae variables and the expansive size of M31 on the sky, it is clear that a survey of these stars sampling a diversity of regions in Andromeda will provide valuable insights into the star formation and chemical enrichment history of our nearest spiral neighbor.

With this in mind, this paper presents the results of archival HST/ACS observations showcasing the RR Lyrae population in the inner regions of the M31 spheroid. The next section describes the observational material and the photometric procedure. We move on to describe the technique used to identify and characterize the variable stars in Sec. 3. The results of this study are described in Sec. 4, and a discussion of these results within the broader context of the M31 halo are presented in Sec. 5. Our conclusions are then summarized in Sec. 6.

2 Observations

The observations used in the present study were obtained with the Hubble Space Telescope Advanced Camera for Surveys (HST/ACS) in parallel with the imagery conducted by program GO-10572. The primary goal of this program was to obtain a deep color-magnitude diagram of the envelope of M32, using the High Resolution Channel (HRC) of the ACS. The total envelope exposure was 32 orbits, split between two filters. An identical set of HRC exposures was later obtained in a background field selected to represent the M31 disk+halo contribution to the M32 envelope exposures. The present images are the parallel observations associated with each pointing obtained with the ACS Wide Field Channel (WFC) using the F606W (V) filter. Table 1 provide some details of the observational data. The temporal coverage is 2.2 days for field 1 and 3.1 days for field 2.

Figure 1 shows the locations of these fields relative to M31. While the M32-background field was carefully selected to fall along the M31 isophote that ran through the M32 envelope field, the two fields were significantly separated in time, thus different spacecraft rolls between the two epochs caused the parallel WFC aperture to fall randomly about the primary HRC fields. Field 1 thus samples a region that is 4.5 kpc in projected distance from the center of M31, while Field 2 is located 6.6 kpc from the center. Note that throughout this paper, we adopt an M31 distance modulus of corresponding to a distance of 770 kpc (Freedman & Madore 1990).

The spacecraft was dithered in a complex pattern to both achieve Nyquist-sampling in the HRC and rejection of CCD defects. Each pair of orbits was dithered in a square pattern of 0.5 HRC pixel steps, followed by larger steps to trace a skewed-square spiral of arcsec total amplitude over the 16 total orbits devoted to each filter/field combination. The subpixel dithering to achieve Nyquist sampling in the HRC is not optimal for the larger pixels of the WFC, but the larger-scale dither pattern fortunately served to offer diverse sampling information for the parallel imagery.

3 Reductions

3.1 Photometry of Program Frames

We chose to work on the FLT images as retrieved from the HST archive. These frames have been bias-subtracted and flat-fielded, but, unlike the drizzled (DRZ) images, they retain the geometric distortions of ACS (Mahmud & Anderson 2008). Photometry was performed using the same procedure as Sarajedini et al. (2006). The first step is the application of geometric correction images to the Wide Field Channel 1 and 2 (WFC1 and WFC2, respectively) portions of the FLT images. After this step, the data quality maps are applied where the values of the bad pixels in the science images are set to a number well below the sky background to be sure the photometry software ignores those pixels. At this point, the resultant images are ready to be photometered.

The detection of the stellar profiles and the measurement of magnitudes was done with the DAOPHOT/ALLSTAR/ALLFRAME crowded-field photometry software (Stetson 1987; 1994). After the application of the standard FIND and PHOT routines to detect stars and perform aperture photometry on them, ALLSTAR was applied to each of the 32 images in order to derive well-determined positions for all of the stars. In this step and in subsequent ones involving the application of a point-spread function (PSF) in order to determine positions and magnitudes, we made use of the high signal-to-noise PSFs constructed by Sarajedini et al. (2006). The reader is referred to that paper for the details of the PSF construction process.

The stellar positions from the ALLSTAR runs were used to construct a coordinate transformation between each of the 32 images and these were used to combine all of the images into one master frame per field. This combined frame was then input into ALLSTAR, from which a master coordinate list of stellar profiles was constructed. The resultant coordinate list along with the spatial transformation between the images and the PSFs were used in ALLFRAME to derive magnitudes for all detected profiles on each image. At this point, the measurements on each of the individual frames were matched and only stars appearing on all 32 images were kept.

The standardization of the individual magnitudes proceeded in the following manner. First, the correction for the charge transfer efficiency problem was applied using the prescription of Reiss & Mack (2004). The magnitudes were then adjusted to a radius of 0.5 arcsec and corrected for exposure time. Offsets to an infinite radius aperture published by Sirianni et al. (2005) were then applied. Finally, the resultant values were calibrated to the VegaMAG system using the zeropoint for the F606W filter from Sirianni et al. (2005). A correction to this zeropoint amounting to 0.022 mag was applied as a result of a revised calibration of the ACS/WFC photometric performance by Mack et al. (2007). Each of our magnitude measurements is affected by three sources of systematic error: the uncertainty in the aperture corrections (0.02 mag), the error in the correction to infinite aperture (0.00 mag) for the F606W filter, and the error in the VegaMAG zeropoint (0.02 mag).

3.2 Characterization of the Variable Stars

For a given star with 32 magnitudes measurements, we calculated the mean photometric error as returned by ALLFRAME () and the standard deviation of the measurements (). For the first round of variable searching, we considered any star a candidate if  / 3.0. Approximately 3000 stars fit this criterion in each of our two fields.

These stars were then input into our template fitting period-finding algorithm, which is based on the method used by Sarajedini et al. (2006) as originally formulated by Layden & Sarajedini (2000). We have taken the FORTRAN code written for the Layden & Sarajedini (2000) study and rewritten it using the Interactive Data Language (IDL) incorporating a graphical user interface (GUI). The original FORTRAN code used the ‘amoeba’ minimum-finding algorithm exclusively, but our code, dubbed FITLC4, has the option to use a more robust algorithm known as ‘pikaia’ which has its roots in the study of genetics. The software uses 10 template light curves - six ab-type RR Lyraes, two c-type RR Lyraes, one eclipsing binary, and one contact binary. It searches over a period range from 0.2 day to a specified maximum (2.2 days for our field 1 and 3.1 days for field 2) looking for the period that minimizes the value of . This is accomplished with a two step process. First pikaia is used to find the combination of epoch, amplitude, and mean magnitude that minimize at evenly spaced period increments of 0.01 day. Then pikaia is applied again to find the combination of epoch, amplitude, mean magnitude, and period that minimize within 0.01 day of the period with the lowest . The best fitting period from this final step is taken to be the period of the variable. The resultant phased light curves for each star were visually examined, and the stars that presented a compelling case for variability were retained in our final database. Of the 6000 total stars originally fit, 752 exhibit genuine variability as shown by our data.

As a test of our template-fitting method, we have also applied the Lomb-Scargle period-finding algorithm (Scargle 1982; Horne & Baliunas 1986) to the time series photometry of the RR Lyraes in our sample. We find a mean difference of 0.0007d in the periods determined by the two methods throughout the period range of RR Lyraes. In the minority of cases where template-fitting and Lomb-Scargle yield significantly different results, the resultant phased light curves are of significantly higher quality for the former method as compared with the latter. Furthermore, to test for the presence of aliasing effects in our derived periods, we have also examined fitted light curves using periods that correspond to minima near half of the optimum period. In all cases, these fits are clearly inferior to the ones yielded by the optimum period from FITLC.

Tables 2 and 3 list the individual F606W magnitudes of each variable at each epoch wherein 2 450 000 has been subtracted from the epoch value while Tables 4 and 5 list the candidate variables in our two fields along with their properties such as period, amplitude, and mean intensity-weighted magnitude. These stars fall into two broad categories. First, there are those that clearly show variability, but their periods are comparable to or longer than our observing window. These are referred to as ‘long period’ in Tables 4 and 5. There is also one candidate anomalous cepheid in our dataset, which is so indicated in Table 5. The second category includes stars that exhibit clear periodic variability with a period that is significantly shorter than our observing window but longer than 0.2d. These are the stars for which we can be confident of our periods. Some examples of stars with periods longer than our observing window are shown in Fig. 2 while Fig. 3 shows phased light curves of a number of contact and eclipsing binaries in our dataset. Figure 4 displays the phased light curves of all of the RR Lyrae variables for which we have derived periods. 5

All of the stars that exhibit RR Lyrae light curves also have apparent magnitudes in the range one would expect if they are at the distance of M31. Therefore, it is reasonable to assume that most if not all of these objects are RR Lyrae stars belonging to M31 and/or its environs. This assertion will become clearer when we compare the luminosity function (LF) of the non-variable stars with that of the RR Lyraes.

It should be noted that we are much less confident about the properties of the eclipsing and contact binaries that we have identified as compared with the RR Lyraes. This is because we know what period range to expect for the RR Lyraes (0.25d to 0.90d), so that our observing window provides coverage of multiple cycles of variation for a given RR Lyrae star. In contrast, the periods of the eclipsing and contact binaries cannot be similarly constrained so it is difficult for us to ensure that our observing window is sufficient to derive the periods of these variables. As such, we have provided information for these stars (positions, periods, amplitudes, and magnitudes) so that future observers can confirm the nature of their variability, but we will not consider them further here. Instead, for the remainder of this paper, we will limit our discussion to the 681 RR Lyrae variables in our sample and what they reveal about the properties of the M31 system.

3.3 Light Curve Simulations

In order to characterize the possible biases in the derived periods of our variable star sample, we have performed simulations of our light curve fitting technique in the following manner. For the ab-type RR Lyraes, we selected one of the light curve templates (the results are insensitive to the actual ab-type template used) and produced artificial variables with a period range of 0.45 to 0.80 days and amplitudes between 0.3 and 1.3 mag. For the c-type RR Lyraes, a period range of 0.25 to 0.40 days and an amplitude range of 0.2 to 0.5 mag was used. One thousand variables were generated in each case and the mean photometric error at the level of the RR Lyraes was used to populate the light curves using the same observing window as the actual data. These simulated light curves were input into our template light curve fitting software. We are interested in comparing the input periods with the output periods in order to gauge any possible biases present in our analysis method.

Figures 5 (RRab) and 6 (RRc) show the result of these fits for Field 1 wherein the upper panel shows the mean difference between the input and output periods while the lower panel illustrates the differences in the period distributions. The result of the simulations for RR Lyraes in Field 2 are indistinguishable from those in Field 1. Of the 1000 ab-type RR Lyraes generated, none were mistaken for any other type of variable among the 10 light curve templates used in the fitting. For the c-type light curves, 2 of the 1000 generated variables were fit with a contact binary template. We find no significant biases in our determination of the periods for both types of RR Lyraes. As such, we will not apply any sort of correction to our derived periods. As for the errors in the period and amplitude determinations, these simulations suggest that an individual ab-type RR Lyrae has an error of 0.005 day and 0.044 mag, respectively. For a c-type RR Lyrae star, these error values are 0.001 day and 0.022 mag.

4 Results

4.1 Luminosity Functions

Figure 7 displays a comparison of the LFs of the nonvariable stars in the two fields. Both distributions feature a quick rise from brighter magnitudes to fainter ones with a pronounced peak at 25.3 representing the core-helium burning horizontal branch (HB) stars. A sudden drop in both LFs at 27.7 suggests the onset of significant incompleteness as the limit of the photometry is approached. The fact that the HB stars are more than 2 magnitudes brighter than this completeness threshold indicates that our sample of RR Lyrae variable candidates should not be adversely biased by photometric incompleteness.

The two panels of Fig. 8 compare the LF of the nonvariable stars with those of the RR Lyraes in the two observed fields. We have used the intensity-weighted magnitudes listed in Tables 4 and 5 to construct these distributions. Gaussian fits to the regions around the RR Lyrae LF peaks yield for Field 1 and for Field 2, where the errors represent the standard error of the mean combined with the uncertainty in the photometric zeropoint added in quadrature. For the nonvariable stars, these peaks correspond to for Field 1 and for Field 2. The 1- width of these distributions is 0.11 mag. These numbers suggest no significant difference in the mean magnitudes of the RR Lyraes and the nonvariable stars. This serves to confirm our assertion that most if not all of the variable stars in this magnitude range are RR Lyrae variables. In addition, when we combine the RR Lyrae variables from both fields, we find a mean magnitude of on the VEGAmag system. The quoted uncertainty represents the standard error of the mean. When converted to the V-band using the mean offset for RR Lyraes in the middle of the instability strip from B2004 of = 0.08 0.04, we derive (random) (systematic). This compares favorably with the value of based on the average for the ab-type and c-type RR Lyraes from the B2004 study (see Fig. 8). We note in passing that a Gaussian fit to the LF of the B2004 RR Lyraes yields a 1- width of 0.12 mag, which is comparable to the value for the RR Lyraes in the present study.

4.2 Number Ratios

Of the 681 total RR Lyrae stars in our sample, 555 (267 in Field 1 and 288 in Field 2) are of the ab-type with the remainder being c-type (57 in Field 1 and 69 in Field 2). This leads to a ratio of =0.190.02, which is quite different than the value of =0.460.11 inferred from the B2004 data. Therefore, our samples of ab-type and c-type RR Lyraes are a factor of 2 greater and a factor of 2 less, respectively, than what we would expect based on the B2004 field. Taken at face value, this suggests that the old population in the environs of M31 exhibits different pulsation properties at 4–6 kpc as compared with 11 kpc.

To evaluate the validity of this assertion, we need to address the question of incompleteness in our sample of RR Lyraes. Are there significant numbers of RR Lyraes in our fields that we have failed to identify? We begin by noting that B2004 claim that their samples of c-type and ab-type RR Lyraes are complete and not significantly contaminated by dwarf cepheids. Therefore, we can gain some insight by comparing the amplitude distributions of the B2004 RR Lyrae variables with our sample as shown in Fig. 9. This comparison suggests that the amplitude distribution of the B2004 RR Lyraes are consistent with those of our sample. Application of the Kolmogorov-Smirnov test to these distributions confirms this suggestion. The fact that, at the low amplitude end, the two distributions are not substantially different argues that significant numbers of low amplitude RR Lyraes are not missing from our sample.

Another possibility to explain the differences in the ratio between our fields and the one at 11 kpc is that our Field 1 data are significantly influenced by the stellar populations of M32 and not M31. In fact, we find =0.180.0.025 in Field 1 and =0.190.025 in Field 2, which are statistically indistinguishable from each other. In addition, the density of RR Lyrae variables and their period distributions are indistinguishable between fields 1 and 2. For example, for the ab-type variables, Field 1 exhibits a mean period of while Field 2 shows . In the case of the c-type RR Lyraes, the analogous values are and , respectively. These values suggests that both of our fields sample the regions around M31 and are minimally contaminated by M32 RR Lyraes.

If this difference in the ratio between a radial distance of 11 kpc and 4–6 kpc in M31 is real, then it suggests that the RR Lyraes at 11 kpc are more akin to their brethren in Oosterhoff type II globular clusters while those at 4–6 kpc are more like RR Lyraes in Oosterhoff type I clusters. This is based on the fundings of Castellani et al. (2003) who examined the ratio in Galactic globulars. They found that among the 12 clusters with 40 or more variables, = 0.37 for Oosterhoff II clusters and = 0.17 for those of Oosterhoff type I. These compare favorably with the values of = 0.46 for the 11 kpc field and = 0.19 for the 4–6 kpc field.

4.3 Periods, Amplitudes, and Metallicities

The Bailey Diagram for our sample of RR Lyraes is shown in Fig. 10 where we plot the variables in the two fields using different colors. However, it is clear that they occupy the same regions of this diagram. The ab-type RR Lyrae variables are shown with open circles while the c-type stars are plotted as open triangles. The dashed line in Fig. 10 represents the relation exhibited by the RRab stars in the B2004 field. The solid lines are the relations for Oosterhoff I and II globular clusters from Clement (2000). These lines have been adjusted to account for the difference between an amplitude in the V-band and one in the F606W band. Interestingly, the B2004 RR Lyrae relation is closer to the OoI line even though the ratio in the B2004 field is closer to that of OoII clusters. It is unclear why this should be the case.

The B2004 line appears to be offset compared with our data suggesting slightly shorter periods for the RRab variables in our fields. This behavior is further exemplified in Fig. 11 which shows the period distributions in the two fields compared with the mean periods of the ab- and c-type RR Lyraes from B2004. We find mean periods of and . For the B2004 field, these values are and . The mean periods of the c-type variables are statistically indistinguishable from each other but the ab-types in our fields exhibit a somewhat shorter period as compared with those in the B2004 fields.

It is well known that as the metallicity of ab-type RR Lyraes increases, their periods decrease (e.g. Sandage 1993; Layden 1995; Sarajedini et al. 2006). Thus, the period distribution of these stars (Fig. 11) can be converted to a metallicity distribution using equations derived by previous investigators. Using the data of Layden (2005, private communication) for 132 Galactic RR Lyraes in the solar neighborhood, Sarajedini et al. (2006) established a relation between period and metal abundance of the form

(1)

This equation does not take into account the amplitudes of the RR Lyraes even though, as Fig. 10 shows, there is a relation between amplitude and period for the ab-types. The work of Alcock et al. (2000) yielded a period-amplitude-metallicity relation of the form

(2)

where represents the amplitude in the V-band. We applied an 8% increase to the amplitudes to convert them to V-band values (B2004). Figure 12 shows the metallicity distribution function (MDF) for the ab-type RR Lyraes. The top panel compares the results obtained using equations (1) and (2) while the lower panel compares the MDFs for the two fields using Equation (2).

We see in the upper panel of Fig. 12 that, while the two MDFs exhibit very similar peak metallicities, the MDF generated using Eqn (2) displays a more prominent peak. This is representative of the fact that Eqn (2) accounts for the variation of period with amplitude as well as metallicity resulting in a cleaner abundance signature in the MDF. In the lower panel of Fig. 12, we see that the peaks of the RR Lyrae MDFs in our two fields differ by 0.1 dex; we find [Fe/H] = for Field 1 and [Fe/H] = for Field 2, where the errors represent standard errors of the mean. This difference is not statistically significant.

Combining the RR Lyraes in the two fields yields the MDF shown as the solid line in Fig. 13, wherein the binned and generalized histograms are shown. The latter has been constructed using an error of 0.31 dex per star (Alcock et al. 2000). The peak metallicity for our sample of ab-type RR Lyraes is then [Fe/H]= where the error is the standard error of the mean. The systematic error of this measurement is likely to be closer to 0.3 dex. The dotted distributions in Fig. 13 are the binned and generalized histograms for the RRab stars in the sample of B2004 scaled to the same number of ab-type RR Lyraes as in our fields. The peak abundance of this MDF is [Fe/H]=.

There are three observations we can make regarding the appearance of Fig. 13. First, it would seem that the errors on the individual metallicity measurements are significant enough to overwhelm any fine-structure that may be present in the two MDFs. That is to say, both MDFs look essentially like normal distributions. Second, since we have applied the same transformation from period to metallicity to both sets of RR Lyraes, we can assert with significant statistical certainty that the mean metal abundance of the RR Lyraes in the B2004 field is lower than that of the RR Lyraes in our two fields. This difference amounts to and reflects back on the period shift seen in the Bailey Diagram shown in Fig. 10. Third, there are a small but non-negligible number of ab-type RR Lyraes with metallicities above -1 that are not seen in the B2004 field. Given the fact that our field is closer to the central regions of M31 as compared with the B2004, it is possible that these metal-rich RR Lyraes could belong to the bulge or disk of M31. We return to this point in the next section.

One last point needs to be addressed before leaving this section and that is concerned with the M31 distance implied by the RR Lyraes in our sample. Using the relation advocated by Chaboyer (1999) of and a reddening of (Schlegel et al. 1998), we find a distance modulus of . This is consistent with the B2004 value and a number of previous determinations.

5 Discussion

We now seek to place our RR Lyrae abundance results within the broader context of the projected radial metallicity distribution of various populations in the environs of M31. Figure 14 shows this information for a range of stellar populations in and around M31. The metallicities for the RR Lyraes in the two fields considered herein are shown by the filled circles while the open circle represents the RR Lyraes in the B2004 field. The inner-most point is the bulge metallicity from the work of Sarajedini & Jablonka (2005), while the remaining open squares are the bulge/halo points from the work of Kalirai et al. (2006) as shown in their Table 3. The dashed line is the least squares fit to the open squares with a slope of . The other points represent the dwarf spheroidal companions to M31 (crosses, Grebel et al. 2003; Koch & Grebel 2006), the globular cluster G1 (filled square, Meylan et al. 2001), and the furthest globular cluster in M31 (open triangle, Martin et al. 2006). Note that we have adopted the mean metallicity of M32 from the work of Grillmair et al. (1996). The elongated rectangle represents the locations of the halo globular clusters in M33 from Sarajedini et al. (2000). All of these values are based on a distance of (770 kpc) for M31. In cases where an error in the metallicity is not available, we have adopted a value of 0.2 dex.

We see in Fig. 14 a clear representation of the notion that the halo population in M31 does not begin to dominate until a galactocentric distance of 30 kpc, as suggested by a number of authors (Guhathakurta et al. 2005; Irwin et al. 2005; Kalirai et al. 2006; Koch et al. 2007). At this location, we see a transition region between the globular cluster G1 which is consistent with the inner-spheroid metallicity gradient (dashed line) and the dwarf spheroidal galaxies which show no relation between abundance and galactocentric distance. In this sense, it would appear that the RR Lyrae populations in our field and that of B2004 follow the trend outlined by the stellar populations outside of 30 kpc. This suggests that the RR Lyraes at these locations are probably members of the M31 halo rather than its bulge suggesting that the halo can be studied as close as 4 kpc from the center of M31 by focusing on the RR Lyraes.

6 Summary and Conclusions

We have presented F606W (V) observations from the HST archive taken with the Advanced Camera for Surveys of two fields located 4-6 kpc from the center of M31. In these regions, we identify 752 variable stars of which 681 are likely to be bona fide RR Lyraes. From the properties of these stars, we draw the following conclusions.

1) The mean magnitude of the RR Lyrae stars is where the uncertainty combines both the random and systematic errors. This is in good agreement with the results of Brown et al. (2004)

2) The ratio of c-type RR Lyraes to all types is reminiscent of the RR Lyraes in Oosterhoff type I globular clusters in the Milky Way. This ratio is significantly different than the Brown et al. (2004) field at 11 kpc from the center of M31 wherein this ratio is closer to that of Oosterhoff II clusters.

3) When the periods and amplitudes of the ab-type RR Lyraes in our sample are interpreted in terms of metallicity, we find the metallicity distribution function to be indistinguishable from a Gaussian with a peak at [Fe/H]=, where the error is the standard error of the mean. The same analysis applied to the Brown et al. (2004) RR Lyraes yields a peak of [Fe/H]=.

4) Using the RR Lyrae luminosity - metallicity relation advocated by Chaboyer (1999) and a reddening of , we find a distance modulus of for M31.

5) We examine the radial metallicity gradient in the environs of M31 using published values for the bulge and halo of M31 as well as the abundances of the dwarf spheroidal companions and globular clusters of M31. In this context, despite the relative proximity of the RR Lyraes in the present study to the center of M31, their metal abundance is more reminiscent of a halo population than a bulge or disk. Therefore, by using the RR Lyraes as a proxy, the halo can be studied as close as 4 kpc from the center of M31.

We are grateful to Andy Layden, Nathan De Lee, and Karen Kinemuchi for useful conversations as this manuscript was being written. A. S. is grateful for support from NASA through grant AR-11277.01-A from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA under contract NAS5-26555.
Field RA (J2000) Decl. (J2000) Starting Date Datasets Filter Exp Time HJD Range (+2 453 000)
1 00 42 41.2 40 46 38 September 22, 2005 J9H905, J9H906, F606W 16 1136s, 635.97 to 638.25
J9H907, J9H908 16 1177s
2 00 43 20.8 40 57 25 February 9, 2006 J9H913, J9H914, F606W 16 1136s, 775.88 to 778.96
J9H915, J9H916 16 1177s
Table 1: Observing Log
Epoch 001 Mag 001 Err 002 Mag 002 Err 003 Mag 003 Err 004 Mag 004 Err 005 Mag 005 Err
3635.97534180 21.414 0.022 21.960 0.021 24.033 0.033 24.782 0.059 24.639 0.049
3635.99096680 21.417 0.024 21.984 0.017 24.023 0.033 24.826 0.052 24.664 0.049
3636.04003906 21.442 0.019 22.088 0.018 24.024 0.052 24.967 0.065 24.699 0.044
3636.05566406 21.400 0.028 22.032 0.025 24.011 0.021 24.650 0.052
3636.10693359 21.405 0.018 22.051 0.030 24.016 0.051 24.750 0.034 24.604 0.045
3636.12304688 21.384 0.030 22.083 0.027 24.013 0.042 24.582 0.038 24.585 0.046
3636.17358398 21.390 0.018 22.171 0.027 23.998 0.043 24.556 0.039
3636.18969727 21.384 0.025 22.118 0.028 24.607 0.056
3636.70800781 21.329 0.011 22.305 0.027 24.050 0.059 24.706 0.039 24.890 0.037
3636.72363281 21.321 0.016 22.332 0.036 24.036 0.036 24.755 0.031 24.799 0.042
3636.77294922 21.323 0.010 22.382 0.019 24.853 0.044 24.617 0.022
3636.78833008 21.315 0.015 22.339 0.029 24.037 0.035 24.846 0.048 24.552 0.049
3636.83959961 21.313 0.017 22.344 0.035 24.057 0.045 24.784 0.029 24.594 0.055
3636.85571289 21.312 0.024 22.356 0.019 24.018 0.056 24.754 0.058 24.618 0.049
3636.90625000 21.314 0.020 22.344 0.018 24.074 0.043 24.673 0.053 24.619 0.037
3636.92236328 21.288 0.021 22.366 0.040 24.061 0.036 24.554 0.033 24.523 0.054
3637.77368164 21.222 0.014 21.832 0.022 23.992 0.040 24.629 0.037 24.619 0.025
3637.78930664 21.198 0.016 21.805 0.021 24.012 0.022 24.553 0.036 24.640 0.026
3637.83862305 21.197 0.018 21.538 0.033 23.949 0.030 24.672 0.039 24.643 0.040
3637.85424805 21.209 0.011 21.542 0.023 23.994 0.037 24.704 0.048 24.649 0.045
3637.90551758 21.225 0.020 21.477 0.027 23.980 0.034 24.932 0.071 24.646 0.098
3637.92163086 21.192 0.021 21.498 0.028 23.977 0.030 24.875 0.050 24.617 0.062
3637.97216797 21.208 0.022 21.591 0.026 24.882 0.026 24.606 0.087
3637.98803711 21.208 0.014 21.541 0.023 23.987 0.031 24.841 0.044
3638.04028320 21.183 0.017 21.634 0.018 24.000 0.025 24.764 0.032 24.669 0.042
3638.05566406 21.180 0.020 21.655 0.025 24.007 0.025 24.673 0.050 24.594 0.071
3638.10498047 21.186 0.020 21.606 0.021 24.000 0.036 24.594 0.038 24.914 0.036
3638.12060547 21.165 0.015 21.644 0.033 24.063 0.022 24.587 0.026 25.073 0.057
3638.17187500 21.198 0.020 21.692 0.024 24.060 0.034 24.648 0.041 25.115 0.047
3638.18798828 21.173 0.014 21.730 0.031 24.031 0.043 24.639 0.028 25.236 0.091
3638.23852539 21.184 0.015 21.732 0.022 24.043 0.073 24.754 0.025 24.946 0.068
3638.25463867 21.158 0.019 21.750 0.026 24.086 0.035 24.760 0.038 24.909 0.035
Table 2: Raw Light Curves Field 1
Epoch 366 Mag 366 Err 367 Mag 367 Err 368 Mag 368 Err 369 Mag 369 Err 370 Mag 370 Err
3775.87866211 21.896 0.034 22.464 0.029 22.360 0.038 23.676 0.023
3775.89428711 21.955 0.031 22.409 0.050 22.387 0.038 23.583 0.025 23.667 0.036
3775.94409180 21.901 0.024 22.388 0.041 22.347 0.028 23.624 0.024 23.597 0.026
3775.95971680 21.885 0.035 22.443 0.029 22.342 0.038 23.626 0.026 23.664 0.030
3776.01098633 21.930 0.028 22.417 0.043 22.347 0.029 23.686 0.027 23.607 0.020
3776.02685547 21.881 0.034 22.400 0.032 22.387 0.032 23.689 0.036 23.579 0.036
3776.07763672 21.886 0.027 22.384 0.032 22.391 0.035 23.716 0.026 23.584 0.033
3776.09350586 21.914 0.019 22.323 0.063 22.332 0.028 23.688 0.037 23.592 0.022
3777.54418945 21.748 0.044 22.178 0.041 22.234 0.034 23.806 0.070 23.671 0.035
3777.55957031 21.693 0.035 22.174 0.054 22.178 0.030 23.807 0.063 23.741 0.034
3777.60913086 21.706 0.034 22.179 0.049 22.159 0.029 23.836 0.053 23.740 0.041
3777.62475586 21.722 0.043 22.174 0.040 22.053 0.060 23.872 0.066 23.707 0.034
3777.67602539 21.692 0.053 22.166 0.045 22.150 0.029 23.863 0.029 23.698 0.029
3777.69189453 21.711 0.063 22.149 0.033 22.140 0.036 23.888 0.040 23.719 0.042
3777.74243164 21.710 0.060 22.160 0.025 22.158 0.028 23.858 0.029 23.672 0.047
3777.75854492 21.679 0.049 22.156 0.041 22.152 0.029 23.855 0.033 23.664 0.023
3778.41113281 21.662 0.028 22.085 0.020 22.113 0.024 23.397 0.020 23.635 0.055
3778.47485352 21.656 0.032 22.074 0.020 22.128 0.033 23.454 0.029 23.702 0.061
3778.54150391 21.652 0.033 22.067 0.026 22.113 0.035 23.553 0.036 23.899 0.056
3778.55712891 21.636 0.032 22.065 0.024 22.097 0.023 23.515 0.026 23.905 0.059
3778.60839844 21.589 0.043 22.055 0.034 22.081 0.035 23.567 0.030 23.981 0.032
3778.62451172 21.614 0.025 22.052 0.039 22.085 0.033 23.594 0.029 23.941 0.027
3778.67504883 21.618 0.032 22.055 0.035 22.087 0.030 23.584 0.023 23.783 0.038
3778.69116211 21.599 0.044 22.045 0.035 22.059 0.042 23.632 0.034 23.834 0.034
3778.74340820 21.592 0.028 22.056 0.038 22.077 0.036 23.671 0.023 23.735 0.026
3778.75903320 21.609 0.034 22.041 0.031 22.054 0.059 23.721 0.025 23.815 0.040
3778.80786133 21.600 0.027 22.030 0.022 22.055 0.036 23.723 0.018 23.653 0.020
3778.82348633 21.594 0.028 22.053 0.036 22.016 0.036 23.746 0.020 23.687 0.031
3778.87475586 21.581 0.029 22.049 0.045 22.038 0.031 23.779 0.029 23.656 0.021
3778.89086914 21.608 0.025 22.047 0.039 22.029 0.032 23.814 0.030 23.659 0.020
3778.94140625 21.597 0.013 22.040 0.041 22.044 0.023 23.835 0.024 23.638 0.019
3778.95751953 21.597 0.025 22.032 0.038 22.045 0.034 23.845 0.029 23.667 0.028
Table 3: Raw Light Curves Field 2
Star ID RA (J2000) Dec (J2000) Period (days) Amplitude Type
1 0 42 38.35 40 47 8.3 1.551 0.301 21.337 long period
2 0 42 41.92 40 45 19.1 2.559 0.919 22.070 long period
3 0 42 37.94 40 45 18.9 1.408 0.100 24.029 long period
4 0 42 34.90 40 46 4.3 0.387 0.288 24.712 RRc
5 0 42 42.82 40 45 23.6 1.561 0.490 24.685 Eclipsing
6 0 42 34.49 40 46 29.0 1.400 0.246 24.758 Contact
7 0 42 41.61 40 46 7.4 0.660 0.725 24.877 RRab
8 0 42 42.42 40 44 59.8 1.539 0.160 24.820 long period
9 0 42 43.09 40 44 59.0 0.508 0.575 24.859 RRab
10 0 42 36.11 40 47 13.9 2.188 0.130 24.918 long period
11 0 42 43.88 40 44 41.7 0.642 0.825 25.034 RRab
12 0 42 38.30 40 45 58.6 0.743 0.599 24.930 RRab
13 0 42 31.65 40 46 53.8 0.749 0.403 24.988 Contact
14 0 42 37.81 40 45 32.7 0.682 0.937 24.952 RRab
15 0 42 41.33 40 45 18.6 0.697 0.718 25.062 RRab
16 0 42 35.83 40 46 12.0 0.342 0.472 25.025 RRc
17 0 42 44.37 40 45 0.2 0.708 0.803 24.975 RRab
18 0 42 40.85 40 45 1.0 0.488 0.635 25.019 RRab
19 0 42 35.77 40 46 44.1 0.744 0.444 25.086 RRab
20 0 42 38.05 40 46 57.9 0.376 0.377 25.073 RRc
21 0 42 46.29 40 46 3.5 0.805 0.523 25.061 RRab
22 0 42 39.16 40 45 55.6 0.339 0.357 25.095 RRc
23 0 42 33.52 40 46 16.4 0.365 0.459 25.121 RRc
24 0 42 34.23 40 47 28.1 0.611 0.693 25.078 RRab
25 0 42 46.08 40 45 16.1 0.705 0.427 25.154 RRab
26 0 42 34.51 40 47 11.4 0.641 0.616 25.049 RRab
27 0 42 37.99 40 46 49.8 0.555 0.669 25.103 RRab
28 0 42 43.53 40 45 38.6 0.596 0.827 25.117 RRab
29 0 42 43.41 40 46 30.1 0.497 0.991 25.200 RRab
30 0 42 41.43 40 46 10.7 0.328 0.440 25.096 RRc
31 0 42 42.05 40 46 7.1 0.567 0.937 25.138 RRab
32 0 42 43.80 40 46 15.3 0.597 0.633 25.191 RRab
33 0 42 39.84 40 45 50.0 0.355 0.356 25.097 RRc
34 0 42 40.83 40 45 22.0 0.618 0.719 25.186 RRab
35 0 42 42.73 40 45 18.2 0.531 0.749 25.215 RRab
36 0 42 42.68 40 44 44.3 0.689 0.504 25.207 RRab
37 0 42 35.22 40 46 24.8 0.502 1.020 25.130 RRab
38 0 42 44.21 40 45 3.9 0.332 0.413 25.143 RRc
39 0 42 47.25 40 45 21.1 0.627 0.650 25.240 RRab
40 0 42 32.79 40 46 7.9 0.537 0.928 25.079 RRab
41 0 42 45.25 40 45 0.3 0.582 1.016 25.107 RRab
42 0 42 36.42 40 46 1.4 0.648 0.491 25.174 RRab
43 0 42 38.30 40 45 14.6 0.351 0.461 25.172 RRc
44 0 42 42.33 40 46 14.9 0.494 0.967 25.187 RRab
45 0 42 44.21 40 45 44.0 0.545 0.506 25.216 RRab
46 0 42 34.14 40 47 22.1 0.560 0.782 25.213 RRab
47 0 42 31.11 40 46 9.8 0.544 1.050 25.136 RRab
48 0 42 35.42 40 46 32.0 0.488 0.789 25.260 RRab
49 0 42 42.47 40 45 21.0 0.308 0.450 25.185 RRc
50 0 42 36.52 40 45 53.3 0.445 1.122 25.212 RRab
51 0 42 42.84 40 46 18.7 0.680 0.478 25.245 RRab
52 0 42 33.73 40 46 28.0 0.517 0.415 25.199 RRab
53 0 42 44.24 40 46 12.4 0.378 0.326 25.182 RRc
54 0 42 47.19 40 45 51.7 0.522 0.936 25.238 RRab
55 0 42 44.64 40 46 22.2 0.500 0.949 25.143 RRab
56 0 42 47.40 40 45 54.5 0.611 0.479 25.260 RRab
57 0 42 42.89 40 45 52.3 0.578 0.627 25.150 RRab
58 0 42 38.77 40 45 32.4 0.364 0.428 25.177 RRc
59 0 42 47.21 40 45 46.8 0.589 0.649 25.204 RRab
60 0 42 40.82 40 46 40.0 0.698 0.586 25.187 RRab
61 0 42 34.15 40 47 15.2 0.508 0.735 25.156 RRab
62 0 42 36.32 40 46 42.2 0.564 0.784 25.241 RRab
63 0 42 31.84 40 46 48.9 0.583 0.479 25.316 RRab
64 0 42 45.53 40 45 2.3 0.550 0.824 25.222 RRab
65 0 42 46.68 40 45 33.8 0.365 0.388 25.212 RRc
66 0 42 45.53 40 46 13.8 0.503 0.605 25.245 RRab
67 0 42 34.91 40 46 22.5 0.590 0.531 25.313 RRab
68 0 42 38.65 40 45 52.5 0.316 0.403 25.251 RRc
69 0 42 43.64 40 45 49.7 0.566 0.857 25.135 RRab
70 0 42 42.74 40 46 2.6 0.527 0.780 25.276 RRab
71 0 42 33.70 40 46 14.0 0.524 0.721 25.205 RRab
72 0 42 44.27 40 46 19.7 0.318 0.384 25.256 RRc
73 0 42 44.46 40 45 35.5 0.619 0.500 25.333 RRab
74 0 42 46.17 40 46 5.4 0.340 0.431 25.231 RRc
75 0 42 36.52 40 46 44.6 0.303 0.457 25.275 RRc
76 0 42 40.85 40 45 5.1 0.298 0.453 25.273 RRc
77 0 42 35.96 40 47 7.3 0.347 0.382 25.289 RRc
78 0 42 46.84 40 45 39.2 0.610 0.595 25.323 RRab
79 0 42 41.15 40 44 55.0 0.337 0.500 25.231 RRc
80 0 42 34.11 40 47 39.8 0.577 0.583 25.246 RRab
81 0 42 37.41 40 46 28.7 0.515 1.085 25.252 RRab
82 0 42 33.80 40 47 10.5 0.588 0.789 25.235 RRab
83 0 42 44.88 40 44 36.5 0.452 1.133 25.279 RRab
84 0 42 39.82 40 46 54.6 0.583 1.166 25.186 RRab
85 0 42 35.71 40 46 38.3 0.556 0.711 25.243 RRab
86 0 42 33.93 40 47 35.0 0.572 0.669 25.293 RRab
87 0 42 41.91 40 46 2.8 0.334 0.418 25.264 RRc
88 0 42 46.42 40 45 58.8 0.557 0.611 25.249 RRab
89 0 42 42.72 40 44 52.4 0.597 0.605 25.313 RRab
90 0 42 40.66 40 44 57.6 0.569 0.662 25.289 RRab
91 0 42 34.57 40 46 20.9 0.540 0.663 25.312 RRab
92 0 42 40.56 40 45 25.1 0.299 0.383 25.283 RRc
93 0 42 34.05 40 47 20.5 0.585 1.103 25.144 RRab
94 0 42 42.01 40 46 1.6 0.540 0.748 25.280 RRab
95 0 42 46.18 40 46 10.0 0.491 0.896 25.290 RRab
96 0 42 36.45 40 45 36.1 0.504 0.871 25.300 RRab
97 0 42 42.89 40 45 2.6 0.277 0.415 25.306 RRc
98 0 42 46.78 40 46 4.9 0.567 0.795 25.259 RRab
99 0 42 38.40 40 45 12.6 0.562 0.712 25.279 RRab
100 0 42 42.22 40 46 13.0 0.565 0.943 25.333 RRab
101 0 42 34.34 40 45 43.4 0.559 0.467 25.371 RRab
102 0 42 33.73 40 46 47.3 0.471 0.809 25.243 RRab
103 0 42 43.19 40 45 0.2 0.604 0.792 25.218 RRab
104 0 42 39.80 40 46 27.9 0.553 1.010 25.327 RRab
105 0 42 40.80 40 45 5.3 0.519 0.916 25.374 RRab
106 0 42 38.06 40 47 5.8 0.545 0.902 25.273 RRab
107 0 42 46.21 40 45 25.8 0.473 1.146 25.363 RRab
108 0 42 32.59 40 46 53.0 0.512 0.946 25.479 RRab
109 0 42 43.02 40 45 29.8 0.607 0.442 25.318 RRab
110 0 42 38.26 40 45 16.2 0.329 0.344 25.350 RRc
111 0 42 41.85 40 46 21.4 0.540 0.746 25.314 RRab
112 0 42 43.66 40 46 25.8 0.270 0.393 25.384 RRc
113 0 42 41.74 40 46 30.2 0.534 0.768 25.387 RRab
114 0 42 35.06 40 46 1.6 0.548 0.779 25.349 RRab
115 0 42 44.44 40 44 46.7 0.584 0.740 25.316 RRab
116 0 42 36.10 40 46 34.8 0.588 0.612 25.307 RRab
117 0 42 32.46 40 46 14.4 0.591 0.617 25.324 RRab
118 0 42 33.59 40 47 1.3 0.547 0.502 25.403 RRab
119 0 42 39.91 40 46 30.2 0.494 1.095 25.442 RRab
120 0 42 34.26 40 46 22.4 0.481 1.016 25.331 RRab
121 0 42 39.35 40 47 0.6 0.548 0.924 25.464 RRab
122 0 42 36.65 40 46 43.8 0.533 1.035 25.390 RRab
123 0 42 43.62 40 44 50.5 0.469 1.129 25.461 RRab
124 0 42 36.05 40 46 53.7 0.531 1.080 25.428 RRab
125 0 42 36.95 40 46 49.1 0.507 0.807 25.504 RRab
126 0 42 46.13 40 45 24.5 0.511 0.850 25.429 RRab
127 0 42 44.55 40 45 21.3 0.612 0.531 25.390 RRab
128 0 42 32.50 40 46 36.2 0.502 0.982 25.517 RRab
129 0 42 47.76 40 45 43.0 0.471 0.948 25.444 RRab
130 0 42 36.63 40 47 9.2 0.669 0.859 25.273 RRab
131 0 42 34.65 40 46 57.9 0.502 1.051 25.484 RRab
132 0 42 41.78 40 44 52.7 0.484 0.824 25.496 RRab
133 0 42 33.24 40 46 57.0 0.393 0.635 25.569 RRab
134 0 42 44.75 40 45 23.5 0.461 1.232 25.419 RRab
135 0 42 31.51 40 46 27.7 1.776 1.221 25.659 Eclipsing
136 0 42 38.41 40 46 22.4 1.747 0.516 25.642 Eclipsing
137 0 42 42.18 40 45 36.2 0.408 1.049 25.548 RRab
138 0 42 44.46 40 45 19.8 1.056 0.788 25.736 Contact
139 0 42 35.92 40 46 0.5 0.474 1.025 25.919 RRab
140 0 42 37.19 40 47 7.3 1.480 0.751 26.322 Contact
141 0 42 45.35 40 45 22.7 1.311 0.765 26.480 Eclipsing
142 0 42 34.47 40 46 44.5 1.597 0.945 26.490 Contact
143 0 42 40.89 40 47 19.3 2.061 0.252 22.197 long period
144 0 42 44.45 40 47 47.6 1.599 0.345 23.035 long period
145 0 42 37.88 40 48 6.3 1.556 0.505 23.412 long period
146 0 42 36.93 40 48 28.6 2.210 0.659 23.639 long period
147 0 42 38.51 40 48 39.3 1.389 0.339 23.843 long period
148 0 42 40.86 40 48 41.8 1.696 0.974 23.955 long period
149 0 42 45.30 40 48 0.8 1.117 0.375 24.108 Eclipsing
150 0 42 44.36 40 47 59.8 1.724 0.423 24.171 long period
151 0 42 44.30 40 47 45.7 0.354 0.170 24.354 RRc
152 0 42 42.98 40 48 2.6 0.486 0.646 24.585 RRab
153 0 42 37.88 40 48 55.3 0.656 1.117 24.998 RRab
154 0 42 39.50 40 49 3.8 1.344 0.535 24.712 Eclipsing
155 0 42 40.13 40 47 44.9 0.670 0.879 24.966 RRab
156 0 42 46.21 40 48 16.4 0.645 0.606 24.932 RRab
157 0 42 41.28 40 47 40.4 0.562 0.749 24.858 RRab
158 0 42 45.14 40 46 35.0 0.792 0.735 24.882 RRab
159 0 42 48.57 40 46 45.5 0.343 0.632 24.943 RRc
160 0 42 48.04 40 47 9.4 0.439 0.993 24.922 RRab
161 0 42 50.25 40 47 16.6 0.682 0.820 24.917 RRab
162 0 42 45.20 40 48 5.4 0.611 0.815 24.843 RRab
163 0 42 43.23 40 47 14.6 0.698 0.735 25.047 RRab
164 0 42 48.14 40 47 58.5 0.684 0.818 24.933 RRab
165 0 42 35.85 40 48 24.1 1.529 1.403 25.236 Contact
166 0 42 42.79 40 47 27.4 0.386 0.461 24.986 RRab
167 0 42 43.38 40 47 56.2 0.594 0.550 24.968 RRab
168 0 42 38.36 40 48 37.2 0.589 0.648 25.039 RRab
169 0 42 46.24 40 48 0.3 0.693 0.587 25.017 RRab
170 0 42 47.60 40 46 9.5 0.420 0.346 24.969 RRc
171 0 42 40.38 40 47 2.6 0.332 0.352 25.034 RRc
172 0 42 43.42 40 47 26.2 0.558 0.616 24.985 RRab
173 0 42 37.69 40 47 46.5 0.600 0.841 25.087 RRab
174 0 42 47.19 40 48 5.4 0.364 0.669 24.977 RRab
175 0 42 47.95 40 46 44.7 0.620 0.903 25.082 RRab
176 0 42 42.07 40 47 25.4 0.751 0.643 25.155 RRab
177 0 42 48.49 40 47 56.2 0.630 0.688 25.146 RRab
178 0 42 37.76 40 48 32.9 0.530 0.837 25.109 RRab
179 0 42 43.18 40 46 39.2 0.604 0.792 25.158 RRab
180 0 42 40.13 40 48 32.2 0.559 0.904 25.098 RRab
181 0 42 48.47 40 47 12.5 0.559 0.821 25.117 RRab
182 0 42 47.53 40 46 26.5 0.607 0.664 25.142 RRab
183 0 42 38.49 40 47 37.1 0.613 0.501 25.089 RRab
184 0 42 40.61 40 48 48.2 0.601 0.605 25.165 RRab
185 0 42 39.71 40 47 21.6 0.417 0.567 25.156 RRab
186 0 42 40.26 40 48 6.0 0.541 0.678 25.107 RRab
187 0 42 34.79 40 47 42.9 1.560 1.827 25.335 Contact
188 0 42 44.24 40 46 33.6 0.656 0.482 25.126 RRab
189 0 42 48.53 40 47 59.8 0.553 0.712 25.143 RRab
190 0 42 41.29 40 48 20.9 0.526 0.805 25.155 RRab
191 0 42 46.97 40 46 37.7 0.590 0.697 25.219 RRab
192 0 42 40.18 40 48 45.9 0.570 1.062 25.064 RRab
193 0 42 39.23 40 49 5.4 0.327 0.252 25.111 RRc
194 0 42 46.49 40 47 31.2 0.547 0.631 25.170 RRab
195 0 42 48.20 40 47 12.8 0.814 0.232 25.146 long period
196 0 42 41.44 40 48 47.8 0.345 0.373 25.084 RRc
197 0 42 45.64 40 46 32.5 0.589 0.599 25.169 RRab
198 0 42 36.65 40 47 45.7 0.491 1.010 25.093 RRab
199 0 42 44.01 40 48 6.4 0.610 0.467 25.210 RRab
200 0 42 34.62 40 47 49.9 0.604 0.629 25.246 RRab
201 0 42 46.25 40 48 6.7 0.583 0.601 25.139 RRab
202 0 42 47.12 40 47 35.5 0.535 0.740 25.092 RRab
203 0 42 52.45 40 47 6.2 0.546 0.811 25.216 RRab
204 0 42 44.27 40 47 3.3 0.357 0.455 25.090 RRc
205 0 42 37.55 40 48 9.0 0.471 0.918 25.030 RRab
206 0 42 39.73 40 48 54.6 0.590 0.880 25.232 RRab
207 0 42 39.18 40 49 0.1 0.277 0.410 25.168 RRc
208 0 42 42.72 40 47 24.4 0.384 0.339 25.137 RRc
209 0 42 49.76 40 47 3.4 0.380 0.369 25.154 RRc
210 0 42 37.62 40 47 23.3 0.361 0.384 25.152 RRc
211 0 42 37.66 40 48 55.6 0.665 0.935 25.120 RRab
212 0 42 47.17 40 47 32.7 0.568 0.919 25.143 RRab
213 0 42 50.28 40 47 34.1 0.516 0.923 25.217 RRab
214 0 42 41.64 40 47 44.6 0.729 0.491 25.151 RRab
215 0 42 41.71 40 48 38.3 0.481 0.886 25.126 RRab
216 0 42 46.61 40 47 13.5 0.582 1.230 25.041 RRab
217 0 42 40.65 40 48 36.8 0.675 0.431 25.230 RRab
218 0 42 40.43 40 47 44.8 0.581 0.669 25.150 RRab
219 0 42 43.66 40 47 58.1 0.457 1.240 25.210 RRab
220 0 42 37.60 40 48 8.1 0.537 0.803 25.203 RRab
221 0 42 42.72 40 48 39.9 0.505 1.093 25.179 RRab
222 0 42 51.34 40 47 8.3 0.299 0.398 25.229 RRc
223 0 42 45.73 40 47 38.2 0.541 0.803 25.194 RRab
224 0 42 49.71 40 47 17.0 0.499 1.045 25.279 RRab
225 0 42 40.73 40 48 18.1 0.517 0.710 25.169 RRab
226 0 42 51.80 40 46 55.5 0.596 1.014 25.054 RRab
227 0 42 44.19 40 47 52.8 0.315 0.447 25.179 RRc
228 0 42 39.79 40 48 25.8 0.645 0.713 25.232 RRab
229 0 42 41.18 40 48 51.8 0.463 1.065 25.196 RRab
230 0 42 44.93 40 47 44.7 0.291 0.362 25.209 RRc
231 0 42 44.77 40 47 48.2 0.521 1.126 25.130 RRab
232 0 42 40.01 40 48 27.8 0.526 0.846 25.209 RRab
233 0 42 50.17 40 47 19.5 0.604 0.391 25.259 RRab
234 0 42 42.80 40 47 57.5 0.627 0.705 25.230 RRab
235 0 42 39.33 40 48 0.2 0.310 0.413 25.218 RRc
236 0 42 40.51 40 48 54.9 0.532 1.086 25.162 RRab
237 0 42 43.83 40 46 53.3 0.461 1.139 25.153 RRab
238 0 42 37.39 40 47 56.9 0.493 1.043 25.254 RRab
239 0 42 35.87 40 47 46.3 0.522 0.994 25.191 RRab
240 0 42 45.11 40 46 39.3 0.339 0.446 25.179 RRc
241 0 42 42.18 40 47 26.8 0.542 0.773 25.217 RRab
242 0 42 38.02 40 47 46.1 0.556 0.738 25.282 RRab
243 0 42 50.60 40 47 2.6 0.295 0.455 25.248 RRc
244 0 42 51.13 40 47 14.4 0.522 1.055 25.215 RRab
245 0 42 45.37 40 47 18.8 0.558 1.150 25.226 RRab
246 0 42 38.88 40 47 42.8 0.585 0.663 25.265 RRab
247 0 42 35.01 40 47 56.8 0.592 0.679 25.174 RRab
248 0 42 39.02 40 48 3.5 0.576 0.732 25.242 RRab
249 0 42 50.40 40 46 51.6 0.571 0.812 25.279 RRab
250 0 42 41.51 40 47 35.9 0.537 0.490 25.213 RRab
251 0 42 45.97 40 47 43.2 0.303 0.520 25.234 RRc
252 0 42 44.51 40 48 8.1 0.539 0.783 25.232 RRab
253 0 42 39.39 40 47 40.6 0.528 0.859 25.267 RRab
254 0 42 45.81 40 46 25.0 0.288 0.471 25.243 RRc
255 0 42 40.59 40 47 4.0 0.596 0.992 25.227 RRab
256 0 42 51.93 40 47 35.7 0.552 0.918 25.177 RRab
257 0 42 39.84 40 47 51.1 0.654 0.679 25.113 RRab
258 0 42 47.05 40 46 46.9 0.501 1.028 25.214 RRab
259 0 42 49.02 40 46 27.3 0.287 0.411 25.281 RRc
260 0 42 40.62 40 48 48.0 0.514 0.920 25.263 RRab
261 0 42 50.35 40 47 44.8 0.326 0.367 25.234 RRc
262 0 42 42.07 40 47 42.0 0.322 0.423 25.244 RRc
263 0 42 49.46 40 47 47.8 0.798 0.419 25.240 Contact
264 0 42 42.52 40 47 33.7 0.553 0.754 25.247 RRab
265 0 42 46.69 40 46 25.0 0.332 0.393 25.277 RRc
266 0 42 47.09 40 48 6.0 0.474 0.953 25.254 RRab
267 0 42 51.91 40 47 19.5 0.695 0.719 25.103 RRab
268 0 42 45.97 40 46 31.3 0.292 0.387 25.259 RRc
269 0 42 49.30 40 46 7.4 0.570 0.626 25.196 RRab
270 0 42 43.09 40 48 9.6 0.543 0.823 25.274 RRab
271 0 42 46.00 40 46 53.7 0.585 0.607 25.296 RRab
272 0 42 42.26 40 48 19.0 0.601 0.611 25.210 RRab
273 0 42 40.29 40 48 23.6 0.582 0.637 25.314 RRab
274 0 42 48.66 40 47 30.5 0.499 1.055 25.334 RRab
275 0 42 37.54 40 47 23.6 0.537 0.809 25.320 RRab
276 0 42 36.91 40 47 54.5 0.593 0.817 25.229 RRab
277 0 42 48.33 40 46 19.3 0.580 0.662 25.344 RRab
278 0 42 39.26 40 47 49.1 0.539 0.903 25.243 RRab
279 0 42 42.99 40 47 59.0 0.507 1.000 25.282 RRab
280 0 42 45.42 40 47 35.9 0.561 0.768 25.313 RRab
281 0 42 37.07 40 47 42.5 0.564 0.727 25.255 RRab
282 0 42 36.62 40 48 39.9 0.581 1.055 25.278 RRab
283 0 42 41.55 40 47 23.4 0.490 0.955 25.345 RRab
284 0 42 44.28 40 46 43.1 0.455 0.955 25.245 RRab
285 0 42 50.18 40 46 23.6 0.519 0.985 25.316 RRab
286 0 42 46.25 40 47 8.7 0.364 0.385 25.290 RRc
287 0 42 39.75 40 47 35.5 0.512 0.595 25.294 RRab
288 0 42 45.47 40 47 38.5 0.661 1.050 25.044 RRab
289 0 42 41.69 40 46 57.4 0.304 0.479 25.310 RRc
290 0 42 50.31 40 46 37.8 0.478 0.676 25.279 RRab
291 0 42 41.11 40 48 32.6 0.292 0.394 25.293 RRc
292 0 42 41.10 40 48 29.1 0.464 1.208 25.217 RRab
293 0 42 45.52 40 46 23.1 0.548 0.738 25.281 RRab
294 0 42 39.67 40 47 4.9 0.577 0.833 25.415 RRab
295 0 42 42.49 40 47 8.7 0.485 1.055 25.187 RRab
296 0 42 49.60 40 46 22.3 0.518 0.960 25.322 RRab
297 0 42 40.04 40 48 56.8 0.537 0.805 25.294 RRab
298 0 42 47.29 40 47 45.5 0.295 0.431 25.323 RRc
299 0 42 39.26 40 47 21.8 0.525 1.238 25.326 RRab
300 0 42 48.48 40 46 54.2 0.506 0.716 25.337 RRab
301 0 42 43.37 40 46 42.0 0.586 0.868 25.253 RRab
302 0 42 45.54 40 48 18.2 0.477 1.121 25.304 RRab
303 0 42 46.98 40 47 31.6 0.510 0.931 25.296 RRab
304 0 42 46.95 40 46 44.6 0.513 0.903 25.239 RRab
305 0 42 48.86 40 46 27.4 0.258 0.172 25.330 RRc
306 0 42 43.19 40 48 32.1 0.541 0.759 25.392 RRab
307 0 42 35.75 40 47 54.9 0.812 0.314 25.365 Contact
308 0 42 48.80 40 47 18.4 0.561 0.656 25.372 RRab
309 0 42 39.38 40 49 3.2 0.564 0.450 25.400 RRab
310 0 42 51.18 40 46 43.8 0.471 1.092 25.218 RRab
311 0 42 36.50 40 48 35.7 0.465 1.267 25.392 RRab
312 0 42 44.20 40 47 18.8 0.498 1.192 25.278 RRab
313 0 42 47.72 40 46 39.6 0.588 0.643 25.317 RRab
314 0 42 45.97 40 46 59.5 0.473 1.052 25.308 RRab
315 0 42 41.90 40 47 31.8 0.518 0.899 25.386 RRab
316 0 42 40.80 40 47 7.0 0.497 0.639 25.368 RRab
317 0 42 48.74 40 47 57.3 0.540 0.906 25.349 RRab
318 0 42 46.34 40 47 22.5 0.452 0.982 25.394 RRab
319 0 42 38.55 40 49 8.2 0.289 0.425 25.367 RRc
320 0 42 38.34 40 48 42.9 0.520 0.997 25.337 RRab
321 0 42 35.87 40 47 36.8 0.490 0.693 25.416 RRab
322 0 42 37.69 40 47 45.7 0.477 1.312 25.305 RRab
323 0 42 46.86 40 46 36.1 0.513 0.941 25.274 RRab
324 0 42 45.40 40 47 5.0 0.549 0.586 25.315 RRab
325 0 42 43.38 40 47 23.4 0.444 1.143 25.337 RRab
326 0 42 48.62 40 46 52.9 0.527 0.903 25.396 RRab
327 0 42 39.86 40 48 41.9 0.522 0.890 25.359 RRab
328 0 42 41.65 40 47 30.0 0.535 1.046 25.295 RRab
329 0 42 43.56 40 46 56.7 0.295 0.397 25.373 RRc
330 0 42 45.68 40 47 54.5 0.498 1.172 25.375 RRab
331 0 42 36.69 40 47 36.0 0.499 0.602 25.387 RRab
332 0 42 50.06 40 46 50.4 0.522 1.220 25.270 RRab
333 0 42 41.87 40 47 30.0 0.569 0.466 25.410 RRab
334 0 42 37.37 40 47 21.4 0.262 0.412 25.422 RRc
335 0 42 39.26 40 47 34.0 0.573 0.852 25.348 RRab
336 0 42 39.08 40 48 58.3 0.590 0.545 25.383 RRab
337 0 42 44.51 40 46 37.5 0.567 0.980 25.361 RRab
338 0 42 46.05 40 47 34.5 1.419 0.466 25.529 Eclipsing
339 0 42 50.62 40 46 47.7 0.484 1.136 25.389 RRab
340 0 42 38.94 40 48 27.3 0.578 0.988 25.312 RRab
341 0 42 47.10 40 46 50.9 0.598 0.885 25.376 RRab
342 0 42 51.60 40 46 51.5 0.519 0.678 25.509 RRab
343 0 42 36.39 40 48 21.3 0.461 0.969 25.527 RRab
344 0 42 40.29 40 48 43.2 0.489 0.809 25.550 RRab
345 0 42 41.30 40 47 22.9 0.494 1.214 25.418 RRab
346 0 42 43.10 40 48 22.2 0.470 0.688 25.602 RRab
347 0 42 48.81 40 47 16.2 0.447 1.204 25.354 RRab
348 0 42 42.52 40 47 11.8 0.467 1.134 25.475 RRab
349 0 42 46.32 40 47 2.3 0.461 0.537 25.600 RRab
350 0 42 35.66 40 48 15.6 1.823 0.668 25.594 Eclipsing
351 0 42 46.69 40 47 48.3 0.437 1.039 25.536 RRab
352 0 42 47.14 40 47 41.5 0.448 1.125 25.564 RRab
353 0 42 46.55 40 47 53.9 1.683 1.143 25.746 Eclipsing
354 0 42 50.43 40 47 38.6 0.400 1.035 25.563 RRab
355 0 42 49.26 40 46 51.5 1.690 1.809 25.935 Eclipsing
356 0 42 39.48 40 48 29.5 1.589 0.856 25.942 Contact
357 0 42 40.64 40 48 45.2 1.360 1.027 25.901 Eclipsing
358 0 42 44.08 40 47 23.5 0.407 0.645 25.922 RRab
359 0 42 49.92 40 46 43.8 0.955 0.713 26.051 Eclipsing
360 0 42 48.05 40 46 50.3 1.714 0.982 26.168 Eclipsing
361 0 42 39.47 40 48 45.2 1.178 0.734 26.081 Eclipsing
362 0 42 45.87 40 46 36.3 1.031 0.821 26.219 Eclipsing
363 0 42 50.80 40 47 24.4 1.045 1.061 26.356 Eclipsing
364 0 42 43.13 40 47 45.4 1.843 1.430 26.397 Eclipsing
365 0 42 43.99 40 46 53.6 1.442 1.071 26.520 Contact
Table 4: Field 1 Variable Stars
Star ID RA (J2000) Dec (J2000) Period (days) Amplitude Type
366 0 43 17.55 40 58 42.3 1.886 0.314 21.732 long period
367 0 43 20.31 40 58 12.1 2.234 0.387 22.141 long period
368 0 43 24.43 40 56 27.8 2.220 0.288 22.146 long period
369 0 43 24.57 40 56 51.9 1.366 0.501 23.625 long period
370 0 43 16.06 40 58 29.2 1.978 0.291 23.675 Eclipsing
371 0 43 23.53 40 57 3.9 0.557 0.558 23.794 RRab
372 0 43 30.90 40 56 53.4 2.575 0.794 24.014 long period
373 0 43 17.54 40 58 48.8 1.142 0.839 24.299 Eclipsing
374 0 43 20.14 40 57 30.7 2.570 0.368 24.386 Contact
375 0 43 20.79 40 57 27.2 0.600 0.563 24.454 RRab
376 0 43 16.09 40 58 42.9 2.029 1.324 24.853 long period
377 0 43 18.98 40 58 9.3 0.449 0.504 24.628 RRab
378 0 43 22.64 40 57 11.6 1.397 0.155 24.631 long period
379 0 43 26.66 40 57 3.9 0.674 0.575 24.716 RRab
380 0 43 25.67 40 56 24.6 0.612 0.437 24.811 RRab
381 0 43 23.34 40 56 44.5 1.215 0.149 24.858 Eclipsing
382 0 43 21.39 40 57 59.0 0.601 1.202 24.821 RRab
383 0 43 29.10 40 57 15.2 0.662 0.834 24.842 RRab
384 0 43 17.96 40 58 26.6 0.803 0.526 24.930 RRab
385 0 43 28.40 40 56 43.7 0.775 0.501 24.927 RRab
386 0 43 26.42 40 57 40.7 0.592 1.104 25.068 RRab
387 0 43 20.39 40 58 38.6 0.769 0.452 24.968 RRab
388 0 43 29.24 40 56 45.7 0.409 0.400 24.992 RRc
389 0 43 17.12 40 58 35.6 0.621 0.893 24.990 RRab
390 0 43 17.65 40 58 26.3 0.673 0.945 24.995 RRab
391 0 43 26.39 40 58 16.4 0.642 1.095 24.988 RRab
392 0 43 16.82 40 58 27.2 0.533 0.945 25.045 RRab
393 0 43 21.13 40 57 30.7 0.762 0.669 24.963 RRab
394 0 43 23.18 40 56 38.3 0.784 0.408 25.052 RRab
395 0 43 23.70 40 57 57.4 0.553 0.972 25.117 RRab
396 0 43 20.11 40 58 53.6 1.397 0.639 25.099 Anomalous Cepheid?
397 0 43 19.38 40 58 16.6 1.873 0.315 24.955 Eclipsing
398 0 43 25.47 40 58 8.2 0.515 0.567 25.071 RRab
399 0 43 25.77 40 56 25.9 0.625 0.414 25.019 RRab
400 0 43 28.42 40 57 35.9 0.710 0.534 25.057 RRab
401 0 43 19.25 40 57 43.8 0.345 0.315 25.041 RRc
402 0 43 16.06 40 58 27.6 0.596 0.894 25.137 RRab
403 0 43 20.64 40 57 24.2 0.635 0.883 25.110 RRab
404 0 43 23.27 40 59 8.0 0.388 0.370 25.082 RRc
405 0 43 26.26 40 56 36.9 0.634 0.744 25.054 RRab
406 0 43 24.14 40 57 37.0 0.368 0.447 25.107 RRc
407 0 43 23.63 40 58 45.7 0.374 0.445 25.059 RRc
408 0 43 23.18 40 58 2.3 0.642 0.966 25.086 RRab
409 0 43 16.06 40 58 25.3 0.722 0.451 25.098 RRab
410 0 43 22.25 40 59 17.6 0.387 0.408 25.041 RRc
411 0 43 19.16 40 57 39.0 0.619 0.620 25.061 RRab
412 0 43 16.38 40 58 33.5 0.379 0.370 25.092 RRc
413 0 43 26.37 40 57 0.8 0.560 0.777 25.192 RRab
414 0 43 20.80 40 58 41.5 0.556 0.858 25.245 RRab
415 0 43 22.33 40 57 34.3 0.598 0.669 25.186 RRab
416 0 43 28.07 40 57 1.1 0.328 0.415 25.110 RRc
417 0 43 26.43 40 58 5.3 0.671 0.693 25.104 RRab
418 0 43 28.05 40 56 58.6 0.706 0.762 25.053 RRab
419 0 43 22.76 40 59 2.5 0.331 0.458 25.166 RRc
420 0 43 29.14 40 56 41.2 0.549 0.948 25.234 RRab
421 0 43 27.51 40 57 21.5 0.508 0.976 25.061 RRab
422 0 43 17.96 40 58 30.6 0.540 0.846 25.281 RRab
423 0 43 19.94 40 58 17.9 0.585 0.975 25.118 RRab
424 0 43 27.62 40 56 17.1 0.470 0.932 25.061 RRab
425 0 43 30.08 40 57 8.2 0.666 0.504 25.143 RRab
426 0 43 17.25 40 58 30.4 0.546 0.893 25.283 RRab
427 0 43 17.11 40 58 50.2 0.579 0.731 25.248 RRab
428 0 43 23.08 40 57 33.8 0.361 0.466 25.146 RRc
429 0 43 25.79 40 57 29.1 0.535 0.684 25.134 RRab
430 0 43 23.18 40 59 16.5 0.454 0.959 25.042 RRab
431 0 43 27.72 40 56 45.3 0.638 0.813 25.095 RRab
432 0 43 25.94 40 57 42.3 0.603 0.717 25.143 RRab
433 0 43 25.28 40 57 49.2 0.353 0.338 25.129 RRc
434 0 43 25.20 40 58 40.4 0.541 1.099 25.160 RRab
435 0 43 22.03 40 59 15.8 0.629 0.457 25.157 RRab
436 0 43 25.56 40 57 57.0 0.469 0.629 25.118 RRab
437 0 43 20.49 40 57 29.9 0.342 0.383 25.178 RRc
438 0 43 22.30 40 58 2.6 0.626 0.529 25.166 RRab
439 0 43 22.78 40 59 20.4 0.360 0.479 25.207 RRc
440 0 43 21.72 40 57 20.9 0.548 0.893 25.320 RRab
441 0 43 16.25 40 58 47.6 0.732 0.612 25.110 RRab
442 0 43 19.41 40 59 6.7 0.672 0.374 25.187 RRab
443 0 43 25.67 40 56 35.5 0.592 0.649 25.142 RRab
444 0 43 19.66 40 57 36.5 0.588 0.731 25.158 RRab
445 0 43 23.27 40 57 24.2 0.573 0.721 25.239 RRab
446 0 43 29.58 40 57 6.2 0.484 1.041 25.102 RRab
447 0 43 22.53 40 56 54.3 0.656 0.591 25.191 RRab
448 0 43 22.19 40 56 50.1 0.366 0.382 25.169 RRc
449 0 43 23.58 40 57 3.7 0.622 0.916 25.183 RRab
450 0 43 25.34 40 58 16.3 0.736 0.698 25.225 Eclipsing
451 0 43 20.72 40 59 14.6 0.376 0.333 25.154 RRc
452 0 43 26.92 40 58 16.9 0.601 0.636 25.237 RRab
453 0 43 29.96 40 56 54.9 0.601 1.007 25.025 RRab
454 0 43 29.91 40 56 58.1 0.524 1.058 25.083 RRab
455 0 43 22.12 40 59 19.4 0.595 0.592 25.261 RRab
456 0 43 22.00 40 59 11.1 0.546 0.699 25.149 RRab
457 0 43 24.45 40 57 55.5 0.510 0.973 25.179 RRab
458 0 43 20.09 40 58 23.6 0.565 0.781 25.251 RRab
459 0 43 20.53 40 57 17.3 0.582 0.684 25.179 RRab
460 0 43 23.59 40 57 41.4 0.578 1.000 24.982 RRab
461 0 43 25.12 40 58 2.2 0.299 0.361 25.208 RRc
462 0 43 25.34 40 56 41.0 0.321 0.399 25.196 RRc
463 0 43 25.26 40 58 27.0 0.304 0.451 25.180 RRc
464 0 43 19.33 40 59 1.0 0.368 0.423 25.209 RRc
465 0 43 19.89 40 58 35.0 0.343 0.482 25.264 RRc
466 0 43 29.02 40 56 31.4 0.353 0.377 25.226 RRc
467 0 43 21.74 40 57 44.2 0.583 0.540 25.288 RRab
468 0 43 27.02 40 56 12.2 0.352 0.378 25.203 RRc
469 0 43 24.07 40 57 52.6 0.567 0.745 25.301 RRab
470 0 43 24.59 40 56 47.8 0.616 0.638 25.239 RRab
471 0 43 27.44 40 58 10.9 0.271 0.451 25.232 RRc
472 0 43 28.05 40 56 34.4 0.450 1.011 25.235 RRab
473 0 43 30.33 40 57 10.1 0.335 0.455 25.206 RRc
474 0 43 18.93 40 58 2.7 0.612 0.746 25.137 RRab
475 0 43 26.54 40 57 34.0 0.537 0.824 25.296 RRab
476 0 43 18.85 40 58 31.2 0.573 0.845 25.248 RRab
477 0 43 23.16 40 56 34.8 0.280 0.478 25.276 RRc
478 0 43 25.07 40 57 6.4 0.341 0.412 25.239 RRc
479 0 43 17.98 40 58 51.1 0.578 0.475 25.258 RRab
480 0 43 22.06 40 57 49.2 0.556 1.005 25.174 RRab
481 0 43 25.06 40 58 11.2 0.322 0.423 25.261 RRc
482 0 43 20.92 40 57 18.2 0.652 0.428 25.224 RRab
483 0 43 20.92 40 57 18.5 0.455 1.123 25.177 RRab
484 0 43 19.89 40 58 1.8 0.585 0.699 25.221 RRab
485 0 43 27.23 40 56 26.7 0.307 0.436 25.272 RRc
486 0 43 18.98 40 59 17.0 0.594 0.715 25.241 RRab
487 0 43 27.67 40 56 54.9 0.281 0.451 25.266 RRc
488 0 43 27.69 40 58 6.7 0.562 0.886 25.267 RRab
489 0 43 17.51 40 57 59.6 0.471 1.069 25.299 RRab
490 0 43 19.47 40 58 33.4 0.512 0.669 25.263 RRab
491 0 43 22.43 40 59 3.2 0.634 1.029 25.168 RRab
492 0 43 22.84 40 59 5.4 0.588 0.809 25.280 RRab
493 0 43 27.79 40 56 26.3 0.509 0.934 25.296 RRab
494 0 43 25.00 40 58 13.4 0.568 0.585 25.330 RRab
495 0 43 19.74 40 59 6.5 0.657 0.829 25.258 RRab
496 0 43 21.99 40 58 2.1 0.576 0.632 25.376 RRab
497 0 43 18.34 40 58 22.4 0.290 0.431 25.328 RRc
498 0 43 24.39 40 58 1.4 0.532 0.809 25.178 RRab
499 0 43 21.14 40 58 26.4 0.489 1.082 25.258 RRab
500 0 43 22.88 40 59 5.0 0.458 0.735 25.356 RRab
501 0 43 23.24 40 58 29.9 0.337 0.375 25.287 RRc
502 0 43 26.11 40 56 3.4 0.453 1.045 25.301 RRab
503 0 43 24.96 40 56 30.7 0.453 0.836 25.190 RRab
504 0 43 28.15 40 56 59.9 0.471 0.882 25.267 RRab
505 0 43 26.41 40 56 38.8 0.451 1.003 25.284 RRab
506 0 43 27.79 40 56 35.4 0.510 1.092 25.195 RRab
507 0 43 23.46 40 57 35.2 0.344 0.380 25.308 RRc
508 0 43 20.12 40 59 9.6 0.308 0.445 25.298 RRc
509 0 43 22.60 40 57 34.0 0.494 0.650 25.329 RRab
510 0 43 27.63 40 56 27.4 0.628 0.399 25.302 RRab
511 0 43 28.09 40 56 33.2 0.484 1.143 25.207 RRab
512 0 43 24.00 40 58 26.0 0.522 0.808 25.264 RRab
513 0 43 21.11 40 58 57.1 0.658 0.535 25.309 RRab
514 0 43 26.25 40 56 39.1 0.531 0.906 25.223 RRab
515 0 43 17.82 40 58 23.5 0.456 1.188 25.370 RRab
516 0 43 19.38 40 58 56.1 0.535 0.773 25.261 RRab
517 0 43 23.79 40 58 5.9 0.477 1.048 25.324 RRab
518 0 43 24.86 40 57 41.9 0.512 1.003 25.231 RRab
519 0 43 20.91 40 58 37.2 0.509 0.946 25.342 RRab
520 0 43 17.34 40 58 35.4 0.564 0.777 25.209 RRab
521 0 43 29.29 40 57 13.1 0.446 0.965 25.290 RRab
522 0 43 21.30 40 58 42.6 0.633 0.515 25.345 RRab
523 0 43 28.67 40 57 26.7 0.562 0.806 25.283 RRab
524 0 43 25.68 40 58 28.3 0.461 1.118 25.348 RRab
525 0 43 23.21 40 57 18.5 0.352 0.404 25.345 RRc
526 0 43 21.63 40 58 57.5 0.558 1.108 25.182 RRab
527 0 43 25.02 40 57 2.7 0.522 0.969 25.257 RRab
528 0 43 27.03 40 57 56.5 0.401 1.148 25.401 RRab
529 0 43 24.66 40 57 16.2 0.409 0.434 25.299 RRc
530 0 43 31.15 40 56 59.9 0.628 0.429 25.366 RRab
531 0 43 20.25 40 59 2.9 0.504 0.997 25.353 RRab
532 0 43 16.91 40 58 52.2 0.483 1.034 25.372 RRab
533 0 43 18.65 40 58 26.9 0.461 1.232 25.322 RRab
534 0 43 24.23 40 57 44.9 0.500 0.716 25.395 RRab
535 0 43 29.16 40 57 2.4 0.571 0.413 25.298 RRab
536 0 43 25.35 40 58 26.6 0.558 1.052 25.479 RRab
537 0 43 22.71 40 57 24.7 0.499 0.786 25.276 RRab
538 0 43 25.85 40 56 54.8 0.406 1.052 25.375 RRab
539 0 43 16.40 40 58 34.6 0.525 0.867 25.301 RRab
540 0 43 21.70 40 59 3.2 0.539 0.763 25.375 RRab
541 0 43 27.09 40 57 25.4 0.456 1.012 25.369 RRab
542 0 43 21.37 40 57 9.4 0.289 0.392 25.375 RRc
543 0 43 24.12 40 57 18.7 0.478 1.125 25.289 RRab
544 0 43 23.12 40 57 5.1 0.538 1.005 25.281 RRab
545 0 43 21.64 40 58 55.1 0.324 0.384 25.372 RRc
546 0 43 21.81 40 59 24.4 0.493 0.985 25.400 RRab
547 0 43 22.91 40 58 40.3 0.476 0.979 25.415 RRab
548 0 43 23.86 40 58 21.2 0.569 0.725 25.291 RRab
549 0 43 20.27 40 57 34.9 0.580 0.815 25.329 RRab
550 0 43 25.55 40 58 11.5 0.437 0.635 25.458 RRab
551 0 43 23.45 40 57 32.1 0.535 0.996 25.380 RRab
552 0 43 22.56 40 58 8.9 0.423 1.426 25.335 RRab
553 0 43 24.18 40 57 50.0 0.478 0.761 25.388 RRab
554 0 43 25.55 40 56 54.1 0.543 0.699 25.366 RRab
555 0 43 16.81 40 58 28.1 0.460 1.192 25.288 RRab
556 0 43 20.99 40 57 32.1 0.575 1.126 25.206 RRab
557 0 43 17.30 40 58 20.7 0.263 0.416 25.484 RRc
558 0 43 22.63 40 57 38.7 0.555 0.839 25.338 RRab
559 0 43 24.33 40 56 54.8 0.572 0.858 25.486 RRab
560 0 43 25.28 40 57 41.1 0.550 0.831 25.350 RRab
561 0 43 24.80 40 58 33.2 0.526 0.781 25.459 RRab
562 0 43 27.89 40 56 23.5 0.513 0.518 25.480 RRab
563 0 43 24.91 40 58 37.2 0.518 0.855 25.522 RRab
564 0 43 16.20 40 58 36.0 0.636 0.701 25.557 RRab
565 0 43 20.17 40 58 58.0 1.461 0.662 25.585 Eclipsing
566 0 43 20.93 40 58 48.4 2.970 0.213 25.574 Eclipsing
567 0 43 24.93 40 58 33.9 0.428 0.958 25.539 RRab
568 0 43 24.15 40 58 48.0 0.527 0.978 25.565 RRab
569 0 43 22.33 40 59 21.8 0.420 0.962 25.583 RRab
570 0 43 21.74 40 57 7.8 0.442 1.158 25.511 RRab
571 0 43 16.66 40 58 43.3 0.298 0.471 25.726 RRc
572 0 43 27.61 40 56 22.4 0.460 1.179 25.725 RRab
573 0 43 26.17 40 57 48.2 1.675 0.856 26.131 Contact
574 0 43 20.90 40 58 20.4 2.440 0.924 26.176 Eclipsing
575 0 43 20.35 40 58 18.0 1.205 0.656 26.243 Contact
576 0 43 25.95 40 57 39.6 1.663 0.734 26.478 Contact
577 0 43 10.05 40 57 47.9 1.889 0.669 22.613 long period
578 0 43 8.11 40 57 24.9 1.945 0.595 22.600 long period
579 0 43 14.56 40 55 55.6 0.978 0.124 22.744 Contact
580 0 43 16.93 40 55 33.4 1.828 0.440 23.351 long period
581 0 43 13.91 40 58 8.1 1.597 0.334 23.486 long period
582 0 43 10.48 40 57 8.1 0.974 0.518 23.514 Contact
583 0 43 19.15 40 55 20.5 1.955 0.434 23.671 long period
584 0 43 8.85 40 57 27.4 2.648 0.310 23.797 Contact
585 0 43 21.71 40 56 32.8 1.723 0.386 24.609 Contact
586 0 43 21.07 40 55 56.8 0.545 1.039 24.730 RRab
587 0 43 10.68 40 57 33.0 0.744 0.616 24.759 RRab
588 0 43 8.64 40 57 20.1 0.300 0.251 24.843 RRc
589 0 43 12.16 40 57 57.2 0.724 0.596 24.822 RRab
590 0 43 14.51 40 56 25.0 0.588 1.115 24.924 RRab
591 0 43 16.38 40 55 35.9 0.697 0.627 24.962 RRab
592 0 43 14.93 40 58 15.9 0.476 0.792 24.917 RRab
593 0 43 17.18 40 56 24.3 0.720 0.704 24.930 RRab
594 0 43 11.81 40 57 16.8 0.685 0.852 24.928 RRab
595 0 43 17.28 40 56 39.7 0.636 0.779 24.970 RRab
596 0 43 20.59 40 56 31.0 0.713 0.779 25.012 RRab
597 0 43 11.87 40 56 36.9 0.586 0.912 25.034 RRab
598 0 43 11.18 40 57 17.7 0.605 0.936 24.996 RRab
599 0 43 22.94 40 55 41.0 0.662 0.785 25.020 RRab
600 0 43 15.95 40 58 8.1 0.662 0.839 25.014 RRab
601 0 43 21.13 40 55 46.5 0.604 1.016 25.038 RRab
602 0 43 16.86 40 57 11.0 0.554 0.849 25.103 RRab
603 0 43 19.62 40 55 9.2 0.692 0.663 25.060 RRab
604 0 43 21.47 40 56 51.3 0.586 0.830 24.952 RRab
605 0 43 22.66 40 55 37.7 0.353 0.289 25.013 RRc
606 0 43 15.02 40 56 53.1 0.569 0.976 25.088 RRab
607 0 43 19.29 40 55 33.0 0.720 0.567 25.030 RRab
608 0 43 19.00 40 55 43.5 0.762 0.566 25.048 RRab
609 0 43 20.05 40 56 26.7 0.592 0.906 25.072 RRab
610 0 43 15.32 40 57 26.4 0.658 0.849 25.048 RRab
611 0 43 11.54 40 56 35.2 0.569 0.866 25.051 RRab
612 0 43 12.87 40 57 31.7 0.584 1.004 25.175 RRab
613 0 43 12.68 40 56 29.0 0.360 0.384 25.052 RRc
614 0 43 20.13 40 57 6.2 0.702 0.830 25.017 RRab
615 0 43 17.47 40 57 45.6 0.276 0.376 25.064 RRc
616 0 43 9.51 40 57 6.9 0.549 0.863 25.008 RRab
617 0 43 20.15 40 55 28.6 0.355 0.468 25.041 RRc
618 0 43 12.46 40 57 1.5 0.359 0.358 25.072 RRc
619 0 43 19.98 40 56 38.6 0.604 0.936 25.039 RRab
620 0 43 13.39 40 57 19.5 0.659 0.624 25.058 RRab
621 0 43 20.17 40 56 2.0 0.568 1.167 25.139 RRab
622 0 43 16.20 40 56 55.6 0.522 0.893 25.037 RRab
623 0 43 20.95 40 55 12.8 0.642 0.611 25.132 RRab
624 0 43 16.41 40 56 40.4 0.583 0.655 25.150 RRab
625 0 43 15.80 40 56 57.3 0.524 0.815 25.183 RRab
626 0 43 9.76 40 57 18.3 0.631 0.769 25.083 RRab
627 0 43 14.49 40 57 11.1 0.528 0.624 25.157 RRab
628 0 43 12.94 40 57 57.5 0.453 1.147 25.331 RRab
629 0 43 8.67 40 57 25.5 0.562 0.509 25.188 RRab
630 0 43 13.42 40 56 13.2 0.568 1.052 25.061 RRab
631 0 43 19.93 40 55 59.6 0.660 0.588 25.189 RRab
632 0 43 23.03 40 55 56.3 0.487 1.085 25.179 RRab
633 0 43 12.28 40 56 43.5 0.637 0.790 25.157 RRab
634 0 43 23.20 40 56 27.0 0.320 0.459 25.115 RRc
635 0 43 17.36 40 56 21.1 0.622 0.500 25.123 RRab
636 0 43 16.63 40 55 38.2 0.701 0.564 25.099 RRab
637 0 43 13.22 40 57 47.8 0.569 1.104 25.129 RRab
638 0 43 24.32 40 55 47.8 0.591 1.050 25.048 RRab
639 0 43 19.95 40 55 31.0 0.315 0.434 25.159 RRc
640 0 43 13.49 40 56 27.8 0.452 1.043 25.286 RRab
641 0 43 15.66 40 55 58.8 0.297 0.344 25.159 RRc
642 0 43 16.60 40 57 12.8 0.457 1.104 25.248 RRab
643 0 43 21.83 40 55 38.0 0.555 0.606 25.110 RRab
644 0 43 20.90 40 55 28.7 0.352 0.455 25.129 RRc
645 0 43 15.74 40 56 8.5 0.584 0.751 25.165 RRab
646 0 43 21.73 40 56 19.2 0.654 0.442 25.173 RRab
647 0 43 10.52 40 57 3.4 0.649 0.368 25.178 RRab
648 0 43 15.20 40 56 46.7 0.344 0.457 25.180 RRc
649 0 43 23.46 40 56 23.2 0.582 0.521 25.245 RRab
650 0 43 15.71 40 57 47.4 0.606 1.050 25.269 RRab
651 0 43 16.83 40 55 43.3 0.504 0.721 25.231 RRab
652 0 43 12.19 40 57 7.0 0.349 0.539 25.145 RRc
653 0 43 23.53 40 55 35.7 0.620 0.525 25.198 RRab
654 0 43 17.59 40 57 27.5 0.497 1.050 25.131 RRab
655 0 43 17.18 40 57 5.6 0.281 0.444 25.201 RRc
656 0 43 20.09 40 56 38.0 0.585 1.045 25.173 RRab
657 0 43 18.87 40 57 4.4 0.497 1.208 25.092 RRab
658 0 43 16.19 40 57 32.0 0.567 0.979 25.236 RRab
659 0 43 15.95 40 56 41.5 0.629 0.592 25.162 RRab
660 0 43 15.17 40 57 27.1 0.590 0.803 25.131 RRab
661 0 43 16.13 40 56 24.6 0.601 1.050 25.093 RRab
662 0 43 13.20 40 58 7.1 0.519 1.090 25.055 RRab
663 0 43 9.54 40 57 12.5 0.503 1.327 25.180 RRab
664 0 43 16.80 40 56 23.4 0.509 1.013 25.133 RRab
665 0 43 16.39 40 57 24.2 0.571 0.657 25.213 RRab
666 0 43 12.42 40 57 13.0 0.575 0.802 25.241 RRab
667 0 43 20.38 40 55 30.5 0.586 0.671 25.177 RRab
668 0 43 10.89 40 57 54.3 0.585 0.545 25.112 RRab
669 0 43 11.84 40 56 40.1 0.537 0.786 25.255 RRab
670 0 43 13.77 40 57 7.6 0.579 1.049 25.038 RRab
671 0 43 17.11 40 57 26.5 0.502 1.077 25.142 RRab
672 0 43 21.35 40 56 39.1 0.618 0.858 25.221 RRab
673 0 43 15.90 40 55 47.5 0.499 0.919 25.207 RRab
674 0 43 10.28 40 57 30.5 0.541 0.953 25.222 RRab
675 0 43 24.26 40 56 0.9 0.341 0.390 25.192 RRc
676 0 43 15.38 40 56 32.4 0.531 0.875 25.201 RRab
677 0 43 21.86 40 56 41.4 0.358 0.370 25.170 RRc
678 0 43 13.42 40 57 53.9 0.505 1.150 25.369 RRab
679 0 43 11.68 40 56 59.5 0.319 0.370 25.234 RRc
680 0 43 11.47 40 57 33.4 0.300 0.423 25.191 RRc
681 0 43 14.59 40 57 7.7 0.283 0.469 25.225 RRc
682 0 43 15.41 40 56 47.5 0.498 0.746 25.199 RRab
683 0 43 17.09 40 55 47.3 0.556 0.777 25.368 RRab
684 0 43 19.91 40 57 4.8 0.605 0.688 25.164 RRab
685 0 43 21.16 40 56 16.4 0.442 1.239 25.202 RRab
686 0 43 10.13 40 57 9.5 0.573 0.712 25.216 RRab
687 0 43 17.19 40 56 39.1 0.293 0.384 25.251 RRc
688 0 43 17.80 40 56 32.3 0.532 0.879 25.183 RRab
689 0 43 22.06 40 56 17.4 0.292 0.438 25.275 RRc
690 0 43 14.57 40 58 0.1 0.345 0.472 25.169 RRc
691 0 43 11.53 40 57 59.8 0.601 0.654 25.255 RRab
692 0 43 16.02 40 57 37.5 0.290 0.531 25.259 RRc
693 0 43 13.47 40 56 41.6 0.597 0.590 25.329 RRab
694 0 43 14.88 40 57 9.5 0.474 1.153 25.194 RRab
695 0 43 13.86 40 57 37.2 0.352 0.366 25.222 RRc
696 0 43 11.66 40 57 54.7 0.586 0.900 25.169 RRab
697 0 43 16.94 40 56 14.5 0.444 0.669 25.245 RRab
698 0 43 10.20 40 57 5.3 0.578 0.658 25.341 RRab
699 0 43 8.08 40 57 27.5 0.551 0.922 25.201 RRab
700 0 43 12.51 40 56 41.2 0.265 0.413 25.238 RRc
701 0 43 12.77 40 57 28.4 0.592 0.883 25.277 RRab
702 0 43 14.98 40 56 10.0 0.586 0.435 25.256 RRab
703 0 43 16.18 40 56 6.5 0.529 0.669 25.294 RRab
704 0 43 14.94 40 56 15.5 0.591 0.528 25.300 RRab
705 0 43 19.85 40 54 57.6 0.504 1.115 25.292 RRab
706 0 43 14.81 40 55 48.9 0.482 0.691 25.242 RRab
707 0 43 18.16 40 55 14.3 0.619 0.453 25.263 RRab
708 0 43 10.37 40 57 32.3 0.550 0.669 25.184 RRab
709 0 43 17.85 40 55 17.3 0.510 0.998 25.174 RRab
710 0 43 13.95 40 56 50.2 0.590 0.496 25.317 RRab
711 0 43 19.20 40 57 23.5 0.605 0.630 25.268 RRab
712 0 43 16.73 40 57 58.8 0.461 1.042 25.263 RRab
713 0 43 12.67 40 58 12.2 0.542 0.644 25.230 RRab
714 0 43 19.86 40 57 10.8 0.324 0.434 25.262 RRc
715 0 43 18.51 40 55 20.5 0.527 1.050 25.348 RRab
716 0 43 15.63 40 57 26.8 0.565 0.611 25.270 RRab
717 0 43 14.52 40 57 35.6 0.535 0.930 25.176 RRab
718 0 43 11.98 40 58 1.0 0.284 0.463 25.326 RRc
719 0 43 14.24 40 58 4.4 0.459 1.150 25.305 RRab
720 0 43 17.28 40 56 10.4 0.483 0.933 25.265 RRab
721 0 43 11.67 40 57 11.5 0.611 0.571 25.239 RRab
722 0 43 11.88 40 57 18.0 0.534 0.950 25.183 RRab
723 0 43 19.59 40 54 56.8 0.555 1.319 25.141 RRab
724 0 43 12.27 40 57 20.5 0.624 0.479 25.287 RRab
725 0 43 19.15 40 56 20.1 0.449 0.830 25.241 RRab
726 0 43 17.22 40 57 43.2 0.269 0.425 25.297 RRc
727 0 43 16.83 40 55 21.7 0.528 0.618 25.272 RRab
728 0 43 12.35 40 56 60.0 0.572 0.665 25.354 RRab
729 0 43 10.78 40 57 24.3 0.521 0.976 25.281 RRab
730 0 43 14.09 40 58 13.7 0.292 0.436 25.323 RRc
731 0 43 18.09 40 54 59.3 0.507 0.950 25.266 RRab
732 0 43 17.76 40 57 24.7 0.476 1.120 25.252 RRab
733 0 43 18.48 40 56 43.5 0.261 0.398 25.347 RRc
734 0 43 10.09 40 57 37.4 0.557 1.064 25.157 RRab
735 0 43 17.41 40 56 25.9 0.549 1.005 25.256 RRab
736 0 43 9.84 40 57 36.0 0.513 0.880 25.305 RRab
737 0 43 19.06 40 56 25.4 0.492 1.174 25.307 RRab
738 0 43 23.11 40 55 40.0 0.275 0.460 25.369 RRc
739 0 43 20.64 40 55 12.0 0.468 0.958 25.324 RRab
740 0 43 19.31 40 56 23.4 0.429 1.203 25.427 RRab
741 0 43 12.39 40 57 41.1 0.520 1.050 25.348 RRab
742 0 43 14.17 40 56 59.3 0.470 0.920 25.392 RRab
743 0 43 15.75 40 57 33.9 0.558 0.656 25.532 RRab
744 0 43 18.19 40 55 9.1 0.450 1.202 25.322 RRab
745 0 43 19.14 40 55 11.8 0.399 1.239 25.465 RRab
746 0 43 21.80 40 56 15.5 0.456 0.993 25.352 RRab
747 0 43 20.00 40 55 6.8 0.471 1.250 25.360 RRab
748 0 43 20.37 40 57 0.8 0.488 1.219 25.436 RRab
749 0 43 22.33 40 55 29.1 0.483 0.706 25.522 RRab
750 0 43 16.73 40 55 24.0 0.517 0.612 25.526 RRab
751 0 43 14.66 40 58 24.0 3.109 1.092 25.594 Contact
752 0 43 16.90 40 57 0.8 0.576 0.905 25.475 RRab
Table 5: Field 2 Variable Stars
Figure 1: The location of our ACS fields overplotted on a digitized sky survey image in the region of M31. The dwarf elliptical galaxy M32 is near the center of the image. North is up and east is to the left.
Figure 2: Unphased light curves for a sample of our variable stars with periods that are comparable to or longer than our observing window. The numbers refer to the stars in Tables 4 and 5.
Figure 3: Phased light curves for some of the contact and eclipsing binaries identified in this study.
Figure 4: Phased light curves for the 681 RR Lyrae variables identified in this study. The open circles are repeated to complete the light curve for phase less than zero and greater than one.
Figure 5: The results of the light curve simulations performed in order to characterize any biases in our period finding algorithm in the case of the RRab variables. The upper panel plots the variation of input minus recovered period while the lower panel plots the period distribution both as a function of period in days. The solid line is the input distribution while the dashed line represents the recovered one. These simulations suggest that the combination of the input data and the period-finding algorithm do not introduce significant biases in our derived periods.
Figure 6: Same as Fig. 6 except that the simulations have been performed using an c-type RR Lyrae variable light curve.
Figure 7: The luminosity functions (LFs) for the non-variable stars in the two fields studied herein. The solid line in the lower panel is the F606W band LF for the field observed in 2005 (field 1 in Table 1) while the dashed line is the LF for the region observed in 2006 (field 2 in Table 1). The two upper panels show the variation of the photometric error as output by ALLFRAME with magnitude. We have plotted every 10th point to make the appearance of these plots manageable.
Figure 8: The luminosity functions (LFs) for the non-variable stars (dashed lines) compared with those of the RR Lyrae candidates (thin solid lines) in the two fields studied herein (see Table 1). The thicker solid lines represent the RR Lyrae stars from the study of Brown et al. (2004).
Figure 9: The upper panel shows the amplitude distribution of the c-type RR Lyraes from the present study (solid line) and the work of Brown et al. (2004, dotted line) scaled to the same maximum. The lower panel is the same as the upper one except that the ab-type RR Lyraes are plotted.
Figure 10: The Bailey Diagram for the RR Lyrae candidates in our fields. The open circles are the ab-type RR Lyraes while the open triangles represent the c-type variables. The color coding represents the field number with blue being stars observed in field 1 and red those found in field 2. This plot shows that, while the ab- and c-type RR Lyraes occupy their characteristic locations in this diagram, there is no significant difference between the RR Lyraes in the two observed fields. The dashed line shows the relation exhibited by the RRab stars in the field observed by Brown et al. (2004). The solid lines are the relations for Oosterhoff type I and II globular clusters from Clement (2000). These lines have been adjusted to account for the difference between an amplitude in the V-band and one in the F606W band.
Figure 11: The period distributions of the ab-type (solid) and c-type (dotted) RR Lyrae variables. The dashed vertical lines represent the mean periods of these same stars from Brown et al. (2004). While the mean periods of the c-type variables agree between our study and that of Brown et al. (2004), the mean period of the ab-type RR Lyraes is somewhat shorter in our sample as compared with that of Brown et al.
Figure 12: The upper panel shows the metallicity distribution function for our sample of RRab variables using two different formulations for the conversion between period and metal abundance (solid line - Eqn (1), dashed line - Eqn (2)). The lower panel shows the MDFs derived using Eqn (2) for the two observed fields (dashed line - Field 2, solid line - Field 1).
Figure 13: A comparison of the metallicity distribution function derived from the ab-type RR Lyraes from the present study (solid lines) and those from the Brown et al. (2004) study (dotted lines). The latter has been scaled to match the number of ab-type RR Lyraes in our two fields. Both binned and generalized histograms are shown.
Figure 14: A plot of the variation of metal abundance with projected distance from the center of M31. Our results are shown by the filled circles while the mean metallicity of the RR Lyraes studied by Brown et al. (2004) is indicated by the open circle. The inner most open square represents the bulge abundance measured by Sarajedini & Jablonka (2006). The remaining open squares are the bulge/halo points from the work of Kalirai et al. (2006). The dashed line is the least squares fit to these data with a slope of –0.75 0.11. The crosses represent the dwarf galaxies surrounding M31 from the work of Grebel et al. (2003) and Koch & Grebel (2006) whereas the abundance of M32 is taken from Grillmair et al. (1996). The filled square is the well-known massive globular cluster G1 studied by Meylan et al. (2001). The open triangle is the furthest known globular cluster in M31 discovered by Martin et al. (2006). For completeness, the boxed region shows the location of the halo globular clusters in M33 from the work of Sarajedini et al. (2000). All of these points have been scaled to an M31 distance of = 24.43.

Footnotes

  1. Based on observations taken with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Telescope.
  2. The National Optical Astronomy Observatory is operated by AURA, Inc., under cooperative agreement with the National Science Foundation.
  3. slugcomment:
  4. http://www.astro.ufl.edu/cmancone/fitlc.html
  5. The complete figure is only available in the electronic version of the journal.

References

  1. Alcock, C. et al. 2000, AJ, 119, 2194
  2. Alonso-García, J., Mateo, M., & Worthey, G. 2004, AJ, 127, 868
  3. Brown, T. M. et al. 2004, AJ, 127, 2738 (B2004)
  4. Castellani, M., Caputo, F., & Castellani, V. 2003, A&A, 410, 871
  5. Chaboyer, B. 1999, in Post-Hipparcos cosmic candles, edited by A. Heck and F. Caputo. (Dordrecht ; Boston) Astrophysics and space science library, Vol. 237), p.111
  6. Clement, C. M. 2000, in IAU COll. 176, The Impact of Large Scale Surveys on Pulsating Star Research, ed. L. Szabados & D. W. Kurtz (ASP Conf. Ser. 203) (San Francisco:ASP), 266
  7. Clementini, G., Federici, L., Corsi, C., Cacciari, C., Bellazzini, M., & Smith, H. A. 2001, ApJ, 559, L109
  8. Contreras, R., Federici, L., Clementini, G., Cacciari, C., Merighi, R., Kinemuchi, K., Catelan, M., Fusi Pecci, F., Marconi, M., Pritzl, B., & Smith, H. 2008, Memorie della Societa Astronomica Italiana, 79, 686
  9. Dolphin, A. E., Saha, A., Olzsewski, E., Thim, F., Skillman, E. D., Gallagher, J. J., & Hoessel, J. 2004, AJ, 127, 875
  10. Durrell, P. R., Harris, W. E., & Pritchet, C. J. 2001, AJ, 121, 2557
  11. Freedman, W. L., & Madore, B. F. 1990, ApJ, 365, 186
  12. Grebel, E. K., Gallagher, J. S. III, & Harbeck, D. 2003, AJ, 125, 1926
  13. Grillmair, C. et al. 1996, AJ, 112, 1975
  14. Guhathakurta, P. et al. 2005, arXiv preprint (astro-ph/0502366)
  15. Horne, J. H. & Baliunas, S. L. 1986, ApJ, 302, 757
  16. Irwin, M. J., Ferguson, A. M. N., Ibata, R. A., Lewis, G. F., & Tanvir, N. R. 2005, ApJ, 628, L108
  17. Kalirai, J. S. et al. 2006, ApJ, 648, 389
  18. Koch, A., & Grebel, E. K. 2006, 131, 1405
  19. Koch, A., et al. 2008, ApJ, 689, 958
  20. Layden, A. C. 1995, AJ, 110, 2312
  21. Layden A. C., & Sarajedini, A. 2000, AJ, 119, 1760
  22. Mack, J., Gilliland, R. L., Anderson. J., & Sirianni, M. 2007, ISR-ACS 2007-02
  23. Mahmud, N. & Anderson, J. 2008, PASP,120, 907
  24. Martin, N. F. et al. 2006, MNRAS, 371, 1983
  25. Meylan, G. Sarajedini, A., Jablonka, P., Djorgovski, S. G., Bridges, T., & Rich, R. M. 2001, AJ, 122, 830
  26. Mould, J., & Kristian, J. 1986, ApJ, 305, 591
  27. Pritchet, C. J., & van den Bergh, S. 1987, ApJ, 316, 517
  28. Reiss, A., & Mack, J. 2004, ISR-ACS 2004-06
  29. Sandage, A. R. 1993, AJ, 106, 687
  30. Sarajedini, A., Barker, M., Geisler, D., Harding, P., Schommer, R. 2006, AJ, 132, 1361
  31. Sarajedini, A., & Jablonka, P. 2005, AJ, 130, 1627
  32. Scargle, J. D. 1982, ApJ, 263, 835
  33. Sirianni, M. et al. 2005, PASP, 117, 1049
  34. Stetson, P. B. 1987, PASP, 99, 191
  35. Stetson, P. B. 1994, PASP, 106, 250
Comments 0
Request Comment
You are adding the first comment!
How to quickly get a good reply:
  • Give credit where it’s due by listing out the positive aspects of a paper before getting into which changes should be made.
  • Be specific in your critique, and provide supporting evidence with appropriate references to substantiate general statements.
  • Your comment should inspire ideas to flow and help the author improves the paper.

The better we are at sharing our knowledge with each other, the faster we move forward.
""
The feedback must be of minimum 40 characters and the title a minimum of 5 characters
   
Add comment
Cancel
Loading ...
157739
This is a comment super asjknd jkasnjk adsnkj
Upvote
Downvote
""
The feedback must be of minumum 40 characters
The feedback must be of minumum 40 characters
Submit
Cancel

You are asking your first question!
How to quickly get a good answer:
  • Keep your question short and to the point
  • Check for grammar or spelling errors.
  • Phrase it like a question
Test
Test description