Resulting catalogs (below) are also available at MAST as High-Level Science Products (HLSP) at: guvcat-hotstars ; Database DOI: https://doi.org/10.17909/w9k5-tm92

Abstract from paper : We present a catalog of 71,364 UV sources with GALEX FUV-NUV≤0.1mag with SDSS photometry. The limit corresponds to stellar Teff>15,000−20,000K, slightly depending on gravity but nearly reddening-independent for Milky-Way-type dust. Most sources are hot white-dwarfs (WDs) and sub-dwarfs (SDs). Comparing the SED (GALEX FUV, NUV, SDSS u,g,r,i,z) of 35,294 sources having good photometry with colors of stellar models and known objects, we identify 12,404±1871-1267 binary hot-compact stars with a cooler, less-evolved companion (with a possible 8%−15% contamination by low-redshift QSOs), and 22,848±1267-3853 single-star candidates. Single-star counts are an upper limit because pairs of similar stars have single-star-like SED, and hot-WDs with main-sequence companions of certain types (depending on WD's radius) are missed or counted as single in the available wavelength range and selection. The catalog offers unique leverage for identifying hot WDs, elusive at longer wavelengths especially when a cooler, larger companion dominates optical-IR fluxes: 51% of the binary- and 20% of the single-star candidates are previously un-known objects. Gaia DR3 provides a parallax with error≤20% for 34% of the binaries- and 45% of the single-star candidates, allowing Teff, E(B−V), radius and Lbol to be derived from SED analysis. The binary-candidate sample usefully expands the overall current binary-WD census to subpopulations elusive to Gaia and to other searches. The binary fraction among this specific sample of hot-compact objects, albeit with the mentioned biases, b_f>46%, compared with that of their progenitors (>80%−50% for mass range 8−1Msun, Moe 2019), implies a lower merging rate than found for massive stars by Sana et al (2017).

Master Catalog - columns description (Table 1 of the paper)

GUVcat_AISxSDSS_HSpoint (point sources catalog, before culling) Master Catalog of point sources: csv file Master Catalog of point sources: fits file Catalog of 71,364 point-like sources, selected from SDSS tag TYPE='STAR' from 278,375 sources in GUVmatch_AISxSDSS (Bianchi and Shiao 2020) with FUV-NUV less or equal 0.1mag; no other culling. This is the ``master catalog'' used as a starting point; it contains, in addition to the tags from the initial GUVmatch_AISxSDSS, additional information to facilitate the science analysis. Specifically, columns 223-231 contain distilled information from the Simbad match (Section 2.3 in the paper), columns 233-257 contain some parameters from the GALEX best visit (individual observation, see Appendix A in the paper) among the visits from which the source was extracted, and columns 258-314 contain information distilled from the Gaia DR3 match (Section 2.2) including serendipitous detection of variability in the Gaia DR3 database. The columns are described in Table 1 of the paper, that can be downloaded here. See Section 2.1 of the paper for other useful tags, such as ``INLARGEOBJ''; sources in the footprint of stellar clusters are excluded from the analysis in this work, but retained in the master catalog, and may be of interest of a variety of purposes but require careful checks of photometric quality.

GUVcat_AISxSDSS_HSpointXGaiaDR3 GUVcat_AISxSDSS_HSpointXGaia3arcsecREWINDED_noNULLS.csv GUVcat_AISxSDSS_HSpointXGaia3arcsecREWINDED_noNULLS.fits The complete results of the Gaia DR3 cross-match to the 71,364 point-like sources of the master catalog. See Section 2.2 in the paper. Columns 1-222 are from the GUVcat_AISxSDSS_HSpoint catalog. Subsequent columns contain all the tags from the Gaia DR3 source table, followed by the tags from the Gaia DR3 vari_summary table. These files contain the full match output, where all Gaia multiple matches within the match radius are retained, as defined in Section 2.2; in the master catalog only the Gaia tags of the ``primary'' match are distilled, i.e. the only match if MMRANK_GAIA = 0, or the closest among multiple matches (MMRANK_GAIA =1), in order to keep a list of unique sources. Therefore, if multiple matches are found and needs to be examined, they can be found in this catalog.

GUVcat_AISxSDSS_HSpointXvisits GUVcat_AISxSDSS_HSpointXvisits_3arcsec.fits GUVcat_AISxSDSS_HSpointXvisits_3arcsec.csv Match of the master catalog with GALEX database table visitphotoobj , to link each source to all its existing GALEX observations, as described in Appendix A. The full results are given in this catalog. Relevant parameters, such as the number of visits found in FUV and NUV, and the GALEX "best-visit" parameters, are distilled in the master catalog. The file is the full output of all visits returned with sources within 3arcsec of the input list: 352,641 rows. Description for all tags from the visitphotoobj table are found in the MAST Casjobs Context ``GALEX GR6plus7''. Values returned as ``null'' are set to -888.

GUVcat_AISxSDSS_HSpointXsimbad_[5 and 10]arcsec catHSpointXsimbad_5arcsec_1681832401503A.csv catHSpointXsimbad_10arcsec_1681832559998A.csv Full results of the match of GUVcat_AISxSDSS_HSpoint with the Simbad database (Section 2.3), with match radius of 5 and 10arcsec. All the Simbad columns of the resulting matched sources are appended after columns 1-222 from Table 1. The files are the original outputs from the Vizier match. The relevant parameters of the nearest Simbad match, and the number of Simbad matches within 5arcsec and 10arcsec, are also included in the master catalog of point-like sources, see Table 1 - columns 265-271. Values are set to ``=='' if there is no match, and to ``-888.'' if no value of a given tag is given for the match.

GUVcat_AISxSDSS_HSculled GUVcat_AISxSDSS_HSculled.fits GUVcat_AISxSDSS_HSculled.csv The analysis sample of 35,294 sources after removing sources with SDSS saturation, sources with possible inconsistencies between the source measurements in the GALEX FUV and NUV images, and trimming to SDSS photometric errors to less or equal 0.2mag in u, g, r, i as described in Section 3.1. This culled subsample is used for analysis in Section 3.2 and in the discussion. Bulk classification of the sources as "single" or "binary" (according to colors) are given in the last column ("color_locus") (Appendix B in the source paper).