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CATALOGS OF HOT STAR CANDIDATES
From the matched GALEX-SDSS source catalogs described above,
Bianchi et al. 2011, MNRAS, 411, 2770 selected hot star candidates, by extracting the
sources with GALEX UV color FUV-NUV < -0.13mag. This color cut corresponds to Effective Temperature
approximately hotter than 18,000K, the exact value depending on gravity (see Sections 3 and 4 of
the cited paper). While the FUV-NUV color allows one to detect the presence of a hot star,
the combination of UV measurements with an additional optical band provides an approximate separation
between "single" hot stars, and
hot stars with a cooler companion (see Fig.1 of Bianchi 2009, ApSS, 320, 11).
Bianchi et al. (2011, MNRAS, 411, 2770) adopted a color cut of NUV-r >0.1mag to separate
candidate binaries among this sample. Note that the binaries locus is contaminated
by some QSOs with non-canonical UV colors (Bianchi et al. 2009, AJ, 137, 3761), the relative
number of extragalactic sources increases towards fainter magnitudes (Bianchi et al. 2011, ApSS, DOI: 10.1007/s10509-010-0581-x).
The hot-star candidates with NUV-r <0.1mag are mostly single stars, although some types
of binaries are also included in this color locus ; most importantly, serendipitous spectroscopic
follow-up of a
subsample indicates the QSO contamination to be negligible in this selection. Therefore, the purity of the "single hot-star" sample is much higher than for
in the binary locus , and the latter are flagged in the catalogs.
The catalogs may be used by citing the source Bianchi et al. (2011, MNRAS, 411, 2770) (open source).