GUVCAT-HOTSTARS

GALEX Hot Stars Catalog with Corollary Data (GUVCAT-HOTSTARS)

Primary Investigator: Luciana Bianchi

HLSP Authors: Luciana Bianchi

Released: 2024-11-07

Updated: 2024-11-07

Primary Reference(s): Bianchi 2024

DOI: 10.17909/w9k5-tm92

Citations: See ADS metrics

Read Me

Figure 5 in Bianchi 2024. The green line shows the adopted separation between candidate single (green dots) and binary (orange dots) hot evolved stars. Model colors for hot compact stars (log g = 7 and 9, T_eff = 100,000–15,000 K, purple lines), main-sequence stars and supergiants (red and yellow sequences, respectively), sample binaries consisting of a WD of T_eff = 100,000 K, 30,000 K, and 20,000 K (purple, black, and purple, respectively), radius = 0.02R_⊙ and 0.1R_⊙, and a main-sequence or giant star companion of representative spectral types. The QSO locus is also shown (cyan; the large diamond marks redshift = 0). Low-redshift QSOs occupy a locus approximately in the center of this plot, which overlaps with some types of stellar binaries. Model colors are unreddened; thin arrows shown on some models indicate E_B−V= 0.2 mag reddening. Sources with Simbad type = QSO or AGN or Seyfert are overplotted with cyan dots, of larger size than the other sources for visibility, but they are only 941 sources out of the 35,294 total analysis sample; they occupy exactly the locus of the QSO average-template colors for redshift ∼0.5−1.5 (cyan for the standard QSO template, dark blue for the Ly_α-enhanced template of Bianchi et al. 2009). Triangles on the purple single WD sequences (log g = 7 and 9) mark T_eff = 200 kK, 30 kK, 20 kK, and 15 kK.

Overview

GUVCAT-HOTSTARS presents a set of catalogs that are derived from 71,364 GALEX UV sources with GALEX FUV-NUV≤0.1mag with SDSS photometry. The FUV-NUV 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, the author identified 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 unknown 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, Bf>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).

Please see http://dolomiti.pha.jhu.edu/uvsky/GUVcatHS/ for more details and access to the FITS versions for five of the six catalogs offered here.

Data Products

Data file naming convention:

hlsp_guvcat-hotstars_galex_imaging_<targ>_fuv-nuv_v1_cat.csv

where:

<targ> represents the particular set of sources that appear in the catalog (see more detailed descriptions below).

Data file types:

_cat.csv	Source catalog

Data Access

For a full list of all of the column descriptions, please see the attached file and Table 2 of Bianchi 2024.

Catalog Original Filename	MAST Filename	Full Description
GUVcat_AISxSDSS_HSpoint.csv	hlsp_guvcat-hotstars_galex_imaging_aisxsdss-point-magdiff-le-0.1_fuv-nuv_v1_cat.csv	Catalog of 71,364 GALEX UV 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.
GUVcat_AISxSDSS_HSpointXGaia3arcsecREWINDED_noNULLS.csv	hlsp_guvcat-hotstars_galex_imaging_aisxsdss-point-magdiff-le-0.1-x-gaia_fuv-nuv_v1_cat.csv	The complete results of the Gaia DR3 cross-match to the 71,364 GALEX UV sources of the master catalog (top row of this table).
GUVcat_AISxSDSS_HSpointXvisits_3arcsec.fits	hlsp_guvcat-hotstars_galex_imaging_aisxsdss-point-magdiff-le-0.1-x-visits_fuv-nuv_v1_cat.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 of Bianchi 2024. The file is the full output of all visits returned with sources within 3 arcseconds of the input list: 352,641 rows.
catHSpointXsimbad_5arcsec_1681832401503A.csv	hlsp_guvcat-hotstars_galex_imaging_aisxsdss-point-magdiff-le-0.1-x-simbad-5as_fuv-nuv_v1_cat.csv	Full results of the match of GUVcat_AISxSDSS_HSpoint with the Simbad database (Section 2.3 of Bianchi 2024), with match radius of 5 arcseconds.
catHSpointXsimbad_10arcsec_1681832559998A.csv	hlsp_guvcat-hotstars_galex_imaging_aisxsdss-point-magdiff-le-0.1-x-simbad-10as_fuv-nuv_v1_cat.csv	Full results of the match of GUVcat_AISxSDSS_HSpoint with the Simbad database (Section 2.3 of Bianchi 2024), with match radius of 10 arcseconds.
GUVcat_AISxSDSS_HSculled.csv	hlsp_guvcat-hotstars_galex_imaging_aisxsdss-point-magdiff-le-0.1-culled_fuv-nuv_v1_cat.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 0.2 mag 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 Bianchi 2024).

Citations

Please remember to cite the appropriate paper(s) below and the DOI if you use these data in a published work.

Note: These HLSP data products are licensed for use under CC BY 4.0.