PS1+2MASS+WISE High Proper Motion Search

A Search for High Proper Motion T Dwarfs with
Pan-STARRS1 + 2MASS + WISE

Michael C. Liu,11affiliation: Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu HI 96822 USA 22affiliation: Visiting Astronomer at the Infrared Telescope Facility, which is operated by the University of Hawaii under Cooperative Agreement no. NNX-08AE38A with the National Aeronautics and Space Administration, Science Mission Directorate, Planetary Astronomy Program. Niall R. Deacon,11affiliation: Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu HI 96822 USA Eugene A. Magnier,11affiliation: Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu HI 96822 USA Trent J. Dupuy,33affiliation: Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 USA 44affiliation: Hubble Fellow Kimberly M. Aller,11affiliation: Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu HI 96822 USA Brendan P. Bowler,11affiliation: Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu HI 96822 USA Joshua Redstone,55affiliation: Facebook, 1601 S. California Avenue, Palo Alto, CA 94304, USA Bertrand Goldman,66affiliation: Max Planck Institute for Astronomy, Koenigstuhl 17, D-69117 Heidelberg, Germany W. S. Burgett,11affiliation: Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu HI 96822 USA K. C. Chambers,11affiliation: Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu HI 96822 USA K. W. Hodapp,11affiliation: Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu HI 96822 USA N. Kaiser,11affiliation: Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu HI 96822 USA R.-P. Kudritzki,11affiliation: Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu HI 96822 USA J. S. Morgan,11affiliation: Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu HI 96822 USA P. A. Price,77affiliation: Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544, USA J. L. Tonry,11affiliation: Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu HI 96822 USA R. J. Wainscoat11affiliation: Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu HI 96822 USA
Abstract

We have searched 8200 sq. degs for high proper motion (0.5–2.7″/year) T dwarfs by combining first-epoch data from the Pan-STARRS1 (PS1)  Survey, the 2MASS All-Sky Point Source Catalog, and the WISE Preliminary Data Release. We identified two high proper motion objects with the very red colors characteristic of T dwarfs, one being the known T7.5 dwarf GJ 570D. Near-IR spectroscopy of the other object (PSO J043.5395+02.3995  WISEP J025409.45+022359.1) reveals a spectral type of T8, leading to a photometric distance of  pc. The 2.56″/yr proper motion of PSO J043.5+02 is the second highest among field T dwarfs, corresponding to an tangential velocity of  km s. According to the Besançon galaxy model, this velocity indicates its galactic membership is probably in the thin disk, with the thick disk an unlikely possibility. Such membership is in accord with the near-IR spectrum, which points to a surface gravity (age) and metallicity typical of the field population. We combine 2MASS, SDSS, WISE, and PS1 astrometry to derive a preliminary parallax of  mas ( pc), the first such measurement using PS1 data. The proximity and brightness of PSO J043.5+02 will facilitate future characterization of its atmosphere, variability, multiplicity, distance, and kinematics. The modest number of candidates from our search suggests that the immediate (10 pc) solar neighborhood does not contain a large reservoir of undiscovered T dwarfs earlier than about T8.

brown dwarfs — proper motions — solar neighborhood — surveys
slugcomment: ApJL, submitted 07/21/2011, revised 08/30/2011

1 Introduction

The Pan-STARRS1 (PS1) survey (Kaiser et al., 2010) represents the first of a new generation of multi-epoch digital sky surveys. In an effort to identify nearby T dwarfs and rare ultracool dwarfs of interest, we are conducting a proper motion search that combines the first epoch of PS1 data with 2MASS, with initial results from PS1 commissioning data in Deacon et al. (2011). In this Letter, we present the discovery of a very high proper motion late-T dwarf, PSO J043.5395+02.3995 (hereinafter PSO J043.5+02). This object has independently been identified by Scholz et al. (2011) in a search for bright, very red objects in the WISE Preliminary Data Release with proper motions of 0.3″/year. They estimated a spectral type of T8–T10 based on the color, a photometric distance of 5.5 pc, and possible thick disk membership. Our near-IR spectroscopy gives a spectral type of T8, a photometric distance of  pc, and probable thin disk membership.

2 Mining Pan-STARRS1, 2MASS, and WISE

The Pan-STARRS1 survey is obtaining multi-epoch imaging in 5 optical bands (, , , , ) with a 1.8-meter wide-field telescope on Haleakala, Maui. Images are processed nightly through the Image Processing Pipeline (IPP; Magnier, 2006, 2007; Magnier et al., 2008). Photometry is on the AB magnitude scale, and the first generation of astrometry is tied to 2MASS, with limiting uncertainties of 70 mas. Although the PS1 filter system (Stubbs et al., 2010) is very similar to SDSS (Fukugita et al., 1996), there are differences. Most notable are the facts that the  filter is cut off at 840 nm unlike the long-pass filter, and SDSS has no corresponding  band ( nm,  nm), which exploits the excellent red sensitivity of the PS1 detectors.111See also http://svn.pan-starrs.ifa.hawaii.edu/trac/ipp/wiki/PS1_Photometric_System.

We use data from the  Survey, the most time-intensive of the several PS1 surveys. This survey covers the 3 steradians north of declination 30, with each filter observed for a total of 6 epochs over 3 years, and with two exposures at each epoch spaced 30 min apart to identify solar system objects. We used the the IPP software known as DVO (Desktop Virtual Observatory; Magnier, 2006) for managing the large numbers of PS1 detections and enabling large-area cross-correlations (10 objects). We ingested 2MASS into the DVO database to mine the two datasets. At the time we did this (February 2011), PS1 had not yet completed its first sweep of the sky. Since the filters for the  Survey are observed weeks to months apart to optimize sky brightness conditions and parallax factors, we maximized our search area by focusing on the  data alone, rather than employing multi-color criteria covering a smaller patchwork on the sky.

Our search method is described in detail by Deacon et al. (2011). In brief, we identified proper motion candidates by matching PS1  detections with 2MASS band detections, excluding galactic latitudes of and allowing PS1-2MASS separations of 28″. The PS1 data were taken from June 2009 to January 2011, during commissioning and the first year of operations; as 2MASS was in operation from 1997–2001, our search has a mean time baseline of 11 years, leading to a maximum proper motion of 2.7″/yr. We used generous PS1-2MASS color cuts to remove M dwarfs and some instrumental artifacts. False associations, whereby matches between PS1 and 2MASS detections in fact are two distinct stationary objects, were then screened using USNO-B (Monet et al., 2003) and SuperCOSMOS (Hambly et al., 2001), to depths of and  mag. (A separate check of objects with  mag counterparts found no strong T dwarf candidates.) Our search reaches magnitudes of  mag and  mag, with 2MASS setting the search depth for T dwarfs (e.g., Figure 10 of Dupuy & Liu, 2009). Given our limiting magnitudes, our culling process is inevitably incomplete. Indeed, the number of candidates increases at larger proper motions as expected due to the remaining mispairs.

Our core PS1+2MASS search program focuses on objects with 0.8″/year, where the false alarm rate is tractable. However, the release of the WISE Preliminary Data Release (Wright et al., 2010) in May 2011 opened the door to mining higher proper motions, by adding unique color information and an epoch of astrometry from the first half of 2010. We cross-matched our 21,070 high proper motion candidates against the WISE data at the PS1 position and excluded objects with a WISE source at the 2MASS position, returning 8,140 matches. For the 131 objects with  mag, corresponding to spectral type T0 and later, we screened the sample visually to excise image artifacts (using data from all the input surveys) and remaining faint mispairs (using the DSS -band images, as bright early-T dwarfs might have counterparts on the -band plates). For the remaining 58 objects, the separations between the PS1 and WISE positions showed the expected bimodal distribution of small separations (true matches) and large separations (false matches), with a minimum around 4″. Thus, we required the two positions to agree within 4″, leaving 49 objects.

The final sample is illustrated in Figure 1. Two objects stand out as being very red in and having high proper motions. (Objects with proper motions of 0.5″/yr will be discussed in a future paper.) One is the T7.5 dwarf GJ 570D (Burgasser et al., 2000). The other, PSO J043.5395+02.3995222The PS1 name used here is based on the computed position at epoch 2010.0. (WISEP J025409.45+022359.1), was previously unknown at the time. We identified a -only counterpart in the latest SDSS data release (DR8; Aihara et al., 2011). This object’s absence in earlier releases explains why it was not found in past SDSS searches. Similarly, its faint band magnitude excluded it from previous 2MASS searches.

At the time of our search, about 8200 sq. degs had  data and were in the WISE Preliminary Data Release, with about 7800 sq. degs of the area also having  data. (This includes the 74% fill factor for individual PS1 exposures due to gaps between CCDs, masked pixels around bright stars, and bad regions of the detectors.) To check our completeness, we examined the known T dwarfs from Dwarfarchives. Out of the 16 objects that are present in WISE, bright enough to be in 2MASS, and residing within the area imaged by PS-1, we retrieved 12 of them, with the rest being culled during the filtering process described above, e.g., by being too close to a USNO-B source. Thus our estimated completeness is 75%. The other high proper motion object found by Scholz et al. (2011), the T9–T10 dwarf WISEP J1741+2533, was not selected as its sky position did not have  imaging when we did our data-mining.

3 Spectroscopy

We obtained low-resolution (100) spectra of PSO J043.5+02 on 2011 June 25 and July 21 UT from NASA’s Infrared Telescope Facility located on Mauna Kea, Hawaii. The two spectra agree well, but the July one had higher S/N so we use it here. Conditions were photometric with average seeing. We used the near-IR spectrograph SpeX (Rayner et al., 1998) in prism mode with the 0.8″ slit, obtaining 0.8–2.5 µm spectra in a single order. The total on-source integration time was 16 min. We observed the A0V star HD 18571 contemporaneously with PSO J043.5+02 for telluric calibration. All spectra were reduced using version 3.4 of the SpeXtool software package (Vacca et al., 2003; Cushing et al., 2004).

The spectrum shows the strong HO and CH absorption characteristic of late-T dwarfs (Figure 3). We classified PSO J043.5+02 using the five spectral indices from Burgasser et al. (2006b), with spectral types assigned using the polynomial fits from Burgasser (2007). Excluding the saturated CH- index, the average spectral type from the indices was T8.0 with an RMS of 0.14 subclasses. We also computed the and NH- indices of Warren et al. (2007) and Delorme et al. (2008), respectively, and found values similar to known T8 dwarfs (e.g. Burningham et al., 2010).

In addition, we visually classified PSO J043.5+02 by comparing with SpeX prism spectra of late-T dwarf spectral standards. Following the prescription of Burgasser et al. (2006b), the depth of the HO and CH absorption bands were examined, normalizing the spectra of PSO J043.5+02 and the standards at their , , and -band peaks. The agreement with the T8 standard 2MASS J04150935 is excellent, with PSO J043.5+02 showing stronger absorption than the T7.5 dwarf GJ 570D. The T8.5 objects from Delorme et al. (2008) and Burningham et al. (2008) have deeper HO absorption and narrower  and  band continuua than PSO J043.5+02. Thus, the indices and visual typing both give a spectral type of T8.

We fit the solar metallicity BT-Settl-2010 model atmospheres (Allard et al., 2010) to our spectrum. The models span  K ( K) and (cgs; ). We first flux-calibrated our spectrum to the weighted average of the 2MASS  and  band photometry (which is only S/N  5–6 in each filter). Following Bowler et al. (2009) and Cushing et al. (2008), we used a Monte Carlo approach to fit the 0.8–2.4 µm data, excluding the 1.60–1.65 µm region because of the known incompleteness of the methane line list. For each Monte Carlo trial, we changed the flux calibration and spectrum assuming normal distributions for the photometric and spectroscopic uncertainties, respectively. We then fit the model atmospheres to each artificial spectrum and repeated the process 10 times.

The best-fitting model has  K and (Figure 3), comparable to atmosphere fitting results for other comparably late-type objects (e.g. Saumon et al., 2007; Leggett et al., 2007; Liu et al., 2011). The broad-band photometry agrees well with the model, except for where the model is a factor of fainter. The mid-IR colors of late-T dwarfs show significant scatter with spectral type (Figure 3), due to non-equilibrium CO/CH chemistry, metallicity, and surface gravity effects (e.g. Leggett et al., 2010), which are not fully incorporated into current models. This empirical scatter also explains the spectral type of T8–T10 inferred by Scholz et al. (2011) based on the mid-IR colors, compared to the actual type of T8.

4 Physical Properties of PSO J043.5+02

Based on an unweighted fit to 19 objects from L5–T10 with parallaxes and WISE data, we derive a 3rd-order polynomial for the band absolute magnitude where and =15 for L5, =20 for T0, etc. The rms scatter about the fit is only 0.18 mag. This gives a photometric distance of  pc.333Another distance estimate comes from the “spectroscopic parallax” method of Bowler et al. (2009), whereby the model atmosphere fitting produces a distance of  pc where is the object’s radius. The Lyon/Cond evolutionary models (Baraffe et al., 2003) predict a radius of 0.10–0.08  for an effective temperature of 800 K and ages of 1–10 Gyr, resulting in a spectroscopic distance of 10–12 pc. Liu et al. (2011) show that such distances for late-T dwarfs range from 1–2 the parallactic distance.

The 2.56″/yr proper motion of PSO J043.5+02 is exceptional. Among field T dwarfs, the only object with a larger value is the T7.5 dwarf 2MASS J111426 (3.05″/yr; Tinney et al., 2005), which Leggett et al. (2007) characterize as slightly metal-poor ( dex). Our photometric distance of  pc leads to a tangential velocity of  km s. Following Dupuy et al. (2009), we assess the galactic membership of PSO J043.5+02 using an oversampled simulation of the stars within 30 pc from the Besançon model (Robin et al., 2003). The model provides  distributions for thin disk, thick disk, and halo stars. We compute the membership probabilities for PSO J043.5+02 from the fraction of its nearest neighbors that belong to each model population. For  = 87 km s, we find membership probabilities in the thin/thick disk of 0.87/0.13, with 0.01 probability of belonging to the halo. Thus, even though the  of PSO J043.5+02 is large, it is merely on the cusp of thin/thick disk membership, because of the many more thin disk stars (a divide of 0.973/0.026/0.002 between thin disk/thick disk/halo members in this model). Thin disk membership is preferred, even accounting for the measurement uncertainty; at the 1 limits of  (79 and 95 km s), the thin/thick disk probabilities are 0.90/0.10 and 0.77/0.23, respectively.444Out of the current census of 100 T dwarfs with proper motion measurements, only three objects have  km s: 2MASS J111426 (T7.5,  km s; Faherty et al., 2009), ULAS J1319+1209 (T5,  km s; Murray et al., 2011), and ULAS J0926+0835 (T4,  km s; Murray et al., 2011). Murray et al. suggest their two ULAS objects are likely halo objects, based on their kinematics relative to the galactic disk velocity ellipsoid. Our approach finds thick disk membership seems plausible. At the 1 limits on , ULAS J1319+1209 has probabilities of 0.09/0.81/0.10 and 0.00/0.29/0.71 for thin disk/thick disk/halo membership, and ULAS J0926+0835 has 0.07/0.82/0.11 and 0.00/0.15/0.85. Likewise, for 2MASS J111426, we find probabilities of 0.36/0.63/0.01 and 0.02/0.83/0.15, again suggesting thick disk membership.

The near-IR spectrum indicates a metallicity comparable to other field objects (Figure 3). PSO J043.5+02 is very similar to the T8 dwarf 2MASS J041509, which is inferred to have [Fe/H] = 0.0–0.3 and (Saumon et al., 2007). A solar metallicity is also signalled by the  band continuum shape, which is metallicity-sensitive (Burgasser et al., 2006a; Leggett et al., 2007). PSO J043.5+02 shows a more pointed shape than the T7.5 dwarf 2MASS J111426, which is inferred to be sub-solar ([Fe/H] = 0.3; Leggett et al., 2007). Finally, the weaker  band flux of PSO J043.5+02 compared to the T8 dwarf Ross 458C (Goldman et al., 2010; Scholz, 2010) further indicates that PSO J043.5+02 has a metallicity and surface gravity (age) typical of field objects. The youth (150–800 Myr) and metal-richness ([Fe/H] = +0.2–0.3) of Ross 458C reduce the effect of collision-induced HO opacity, leading to brighter  band emission (e.g., Liu et al., 2007).

Our model atmosphere fitting gives a low surface gravity (=4.0); however, the result is ill-constrained, as seen by the  surface (Figure 3). Following Warren et al. (2007), a better constraint comes from comparing PSO J043.5+02 to other late-T dwarfs using the and indices, guided by model atmosphere predictions and empirical benchmarks. In such a representation (e.g., Figure 5 of Liu et al., 2011), PSO J043.5+02 is inferred to have a relatively high surface gravity () based on its large value, consistent with an old (Gyr) age.

PS1  Survey  and  imaging are scheduled to maximize the parallax factor between epochs, with the goal of deriving parallaxes over the entire survey. Given the proxmity of PSO J043.5+02, a preliminary result is possible even with only a 5-month PS1 baseline (3 epochs from 2010.65 to 2011.06, with 2 exposures per epoch), by adding astrometry from 2MASS (2000.73), SDSS (2008.72), and WISE (2010.08). Altogether, these data span a 10-year baseline. For WISE, there are known 05 systematic errors in the Preliminary Release Source Catalog, so we constructed our own astrometric catalog for 1 sq. deg around PSO J043.5+02 from the Preliminary Single Exposure (L1b) Working Database, which we found to be unaffected by such problems. We cross-matched individual WISE detections and used the weighted average and standard error for positions and uncertainties. For 2MASS and SDSS, we assumed relative positional uncertainties of 100 mas and 70 mas, respectively, based on our experience with matching these catalogs to high-precision ( mas) relative astrometry from our parallax program on the Canada-France-Hawaii Telescope (Dupuy, 2010). We then combined all nine astrometric datapoints (2MASS, SDSS, WISE, and 6  PS1), allowing for small shifts and a full linear transformation. We used a Markov Chain Monte Carlo method to determine the posterior distributions of the proper motion and parallax. The best solution had (13 degrees of freedom), validating our astrometric errors. a parallax of  mas (Figure 4), and a proper motion of /yr and . This includes a (negligible) correction from relative to absolute parallax of  mas computed using the Besançon model as described in Dupuy (2010).

5 Discussion

For the median  of 30 km s of ultracool dwarfs within 20 pc (Faherty et al., 2009), our proper motion range of 0.5–2.7″/yr corresponds to distances of 12 pc and 2 pc. (Objects with higher tangential velocities of course can be selected at even larger distances.) This approximate kinematic limit is well-matched to the  mag limit for our search: the three T7.5 dwarfs with 2MASS photometry and parallaxes have  = 15.93, 15.65, and 16.47 mag (HD 3651B, 2MASS J121703, and GJ 570D, respectively) and the T8 dwarf 2MASS J041509 has  mag, meaning our search has a limiting distance of 12 pc for T8 dwarfs (9 pc for the 2MASS full-sky completeness of ). The limiting distance drops precipitously for later types: the T10 dwarf UGPS J072205 (Lucas et al., 2010) at 4 pc has  mag, right at the nominal 2MASS limit.

The modest number of candidates from our search suggests that the immediate (10 pc) solar neighborhood does not contain a large reservoir of undiscovered T dwarfs down to about T8. We found 7–10 candidates (depending on the cutoff used for the PS1-WISE separation) with proper motions of 0.5–2.7″/year and colors of , including 3 previously known objects. In comparison, Dwarfarchives.org lists 30 objects in the same proper motion range and with spectral types of T0–T8 (ignoring 2 tight companions found by adaptive optics imaging). Since our PS1+2MASS+WISE search covered 20% of the sky, a rough estimate based on the known census predicts we should identify about 6 objects, consistent with our findings.

The Pan-STARRS1 surveys have been made possible by the Institute for Astronomy, the University of Hawaii, the Pan-STARRS Project Office, the institutions of the Pan-STARRS1 Science Consortium (http://www.ps1sc.org), and NASA. Our research has employed the WISE, SDSS-III, and 2MASS data products; NASA’s Astrophysical Data System; the SIMBAD database; the M, L, and T dwarf compendium housed at DwarfArchives.org, and the SpeX Prism Spectral Libraries. This research was supported by NSF grants AST-0507833 and AST09-09222 (awarded to MCL), AST-0709460 (awarded to EAM), AFRL Cooperative Agreement FA9451-06-2-0338, and DFG-Sonderforschungsbereich 881 ”The Milky Way”. Finally, the authors wish to recognize the very significant cultural role that the summit of Mauna Kea has always had within the indigenous Hawaiian community. We are most fortunate to conduct observations from this mountain. Facilities: IRTF (SpeX), PS1 (GPC1)

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Figure 1: Our PS1+2MASS candidates as a function of WISE color, proper motion, and reduced proper motion. The black dots show our set of potential PS1+2MASS matches; at high proper motion, most are expected to be false associations. Objects with were further screened, and the red and gold dots show those with WISE counterparts close to the PS1 position. Objects with open symbols have PS1 optical counterparts at  and/or . Known L and T dwarfs from Dwarfarchives.org are plotted as blue squares.
Figure 2: Finding charts for PSO J043.5+02 from SDSS (epoch 2008.72), Pan-STARRS1 (2010.67 for  and 2010.65 for ), 2MASS (2000.73), and WISE (2010.08). The red circles show the object’s position at the 2MASS epoch (dotted line) and the PS1  epoch (solid line). The PS1 inset images are 10″ on a side.
Figure 3: Spectral properties of PSO J043.5+02. Top: Spectrum (black line) compared to other T7.5–T8 dwarfs (Burgasser et al., 2004, 2006a, 2010), normalized to the 1.26–1.27 µm region. The Ross 458C spectrum has been lightly smoothed. Middle: Spectrum compared to the PS1, 2MASS, and WISE photometry (green dots; Table 1) and the best-fitting BT-Settl-2010 model atmosphere ( K,  dex; orange line). The inset contour plot shows the mean surface from our model fitting. The unfilled green triangle shows the 2MASS  band upper limit. Bottom: WISE  color as a function of spectral type, with subsets from Faherty et al. (2009) highlighted in color. This plot shows objects from Dwarfarchives.org with good (unconfused and not blended) WISE data and additional objects from Mainzer et al. (2011) and Gelino et al. (2011). Known binaries and close companions are excluded. When available, optical spectral types are used for M and L dwarfs, with near-IR types for T dwarfs. PSO J043.5+02 is the red star.
Figure 4: Preliminary parallax for PSO J043.5+02. Top panels show relative astrometry in  and  as a function of Julian year after subtracting the best-fit proper motion. (This representation is for display purposes only. Our analysis fits for both the proper motion and parallax simultaneously.) Bottom panels show the residuals after subtracting the parallax and proper motion.
Property Measurement
AstrometryaaThe SDSS, PS1, and WISE astrometry has been tied to common system, using 2MASS as the absolute reference (Section 4). (Equinox 2000)
2MASS RA, Dec (ep 2000.727) 02:54:07.886, +02:23:56.35
SDSS RA, Dec (ep 2008.723) 02:54:09.242, +02:23:58.32
PS1  RA, Dec (ep 2010.651) 02:54:09.575, +02:23:58.68
PS1  RA, Dec (ep 2010.651) 02:54:09.579, +02:23:58.56
PS1  RA, Dec (ep 2010.673) 02:54:09.578, +02:23:58.69
PS1  RA, Dec (ep 2010.673) 02:54:09.581, +02:23:58.56
PS1  RA, Dec (ep 2011.064) 02:54:09.621, +02:23:58.72
PS1  RA, Dec (ep 2011.064) 02:54:09.633, +02:23:58.83
WISE RA, Dec (ep 2010.075) 02:54:09.449, +02:23:58.56
Proper motion amplitude (″/yr)
Proper motion PA ()
Parallax (mas)
Photometry
SDSS (AB mag) 19.86 0.07
PS1  (AB mag) 21.25 0.06bbAverage of multi-epoch photometry.
PS1  (AB mag) 19.11 0.04bbAverage of multi-epoch photometry.
2MASS (mag) 16.56 0.16
2MASS (mag) 15.88 0.20
2MASS (mag) 16.0 (2)
WISE (mag) 15.74 0.07
WISE (mag) 12.71 0.03
WISE (mag) 11.04 0.13
WISE (mag) 9.1 (2)
SpectrophotometryccBroadband photometry was synthesized from our flux-calibrated spectrum, with errors derived from the 2MASS  and  band photometry and the spectrum’s uncertainties. The errors in the synthesized colors are smaller than for the magnitudes, because the colors incorporate only the spectrum’s uncertainties. Note that the synthesized 2MASS color ( mag) is consistent with the T8 spectral type, but different than the  mag from the 2MASS catalog, likely due to underestimated errors in the 2MASS photometry.
MKO (synth) (mag) 16.14 0.12
MKO (synth) (mag) 16.51 0.12
MKO (synth) (mag) 16.84 0.12
MKO (synth) (mag) 0.368 0.002
MKO (synth) (mag) 0.336 0.005
MKO (synth) (mag) 0.704 0.005
2MASS (synth) (mag) 16.43 0.12
2MASS (synth) (mag) 16.47 0.12
2MASS (synth) (mag) 16.69 0.12
2MASS (synth) (mag) 0.044 0.002
2MASS (synth) (mag) 0.213 0.005
2MASS (synth) (mag) 0.257 0.004
HO- 0.039 (T8.2)
CH- 0.192 (T7.9)
HO- 0.175 (T8.0)
CH- 0.121 (T7.9)
CH- 0.059 (T6)
0.321 (T8)
NH- 0.625
0.121
Spectral type T8
Photometric distance (pc)
Table 1: Measurements of PSO J043.5+02 
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