GALEXTDSC ivo://nasa.heasarc/galextdsc NASA/GSFC HEASARC Gezari et al. 2026-10-09 NASA/GSFC HEASARC help desk heasarc-vo at athena.gsfc.nasa.gov Survey Source This table contains results from the selection and classification of over a thousand ultraviolet (UV) variable sources discovered in ~ 40 deg<sup>2</sup> of GALEX Time Domain Survey (TDS) NUV images observed with a cadence of 2 days and a baseline of observations of ~ 3 years. The GALEX TDS fields were designed to be in spatial and temporal coordination with the Pan-STARRS1 Medium Deep Survey, which provides deep optical imaging and simultaneous optical transient detections via image differencing. The authors characterize the GALEX photometric errors empirically as a function of mean magnitude, and select sources that vary at the 5-sigma level in at least one epoch. They measure the statistical properties of the UV variability, including the structure function on timescales of days and years, and report classifications for the GALEX TDS sample using a combination of optical host colors and morphology, UV light curve characteristics, and matches to archival X-ray, and spectroscopy catalogs. The authors classify 62% of the sources as active galaxies (358 quasars and 305 active galactic nuclei), and 10% as variable stars (including 37 RR Lyrae, 53 M dwarf flare stars, and 2 cataclysmic variables). They detect a large-amplitude tail in the UV variability distribution for M-dwarf flare stars and RR Lyrae, reaching up to |Delta-M| = 4.6 and 2.9 magnitudes, respectively. The mean amplitude of the structure function for quasars on year timescales is five times larger than observed at optical wavelengths. The remaining unclassified sources include UV-bright extragalactic transients, two of which have been spectroscopically confirmed to be a young core-collapse supernova and a flare from the tidal disruption of a star by a dormant super-massive black hole. The authors calculate a surface density for variable sources in the UV with NUV < 23 mag and |Delta-M| > 0.2 mag of ~ 8.0, 7.7, and 1.8 deg<sup>-2</sup> for quasars, AGN, and RR Lyrae stars, respectively, and a surface density rate in the UV for transient sources, using the effective survey time at the cadence appropriate to each class, of ~15 and 52 deg<sup>-2</sup> yr<sup>-1</sup> for M dwarfs and extragalactic transients, respectively. The GALEX observations were made using the NUV detector which has an 1.25 degree diameter field of view and an effective wavelength of 2316 Angstroms. During the window of observing visibility of each GALEX TDS field (from two to four weeks, one to two times per year), they were observed with a cadence of 2 days, and a typical exposure time per epoch of 1.5 ks (or a 5-sigma point-source limit of m<sub>AB</sub>(NUV) ~ 23.3 magnitude), with a range from 1.0 to 1.7 ks. Table 2 in the reference paper lists the RA and Dec of their centers, the Galactic extinction E(B - V ) for each field from the Schlegel et al. (1998, ApJ, 500, 525) dust maps, and the number of epochs per field. This table was created by the HEASARC in May 2013 based on a machine-readable version of Table 4 from the paper which was obtained from the ApJ web site. This is a service provided by NASA HEASARC . 2013ApJ...766...60G https://heasarc.gsfc.nasa.gov/W3Browse/all/galextdsc.html Catalog Research served-by HEASARC TAP https://heasarc.gsfc.nasa.gov/xamin/vo/cone?showoffsets&table=galextdsc& GET text/xml 180 99999 true 53.2683 -29.2079 0.0166666666666667 https://heasarc.gsfc.nasa.gov/xamin/vo/tap https://heasarc.gsfc.nasa.gov/cgi-bin/W3Browse/getvotable.pl?name=galextdsc GET text/xml https://heasarc.gsfc.nasa.gov/cgi-bin/W3Browse/w3query.pl?tablehead=name=heasarc_galextdsc&Action=More+Options&Action=Parameter+Search&ConeAdd=1 GALEX 0.0166666666666667 UV public galextdsc GALEX Time Domain Survey Catalog name GALEX TDS Designation meta.id;meta.main char nullable ra Right Ascension degree pos.eq.ra;meta.main double nullable dec Declination degree pos.eq.dec;meta.main double nullable host_rmag Optical Host r-Band Magnitude mag phot.mag;em.opt.R double nullable nuv_mag_low_limit Limit Flag for mlow meta.code;phot.mag;em.UV.200-300nm char nullable nuv_mag_low Low-State NUV Magnitude mag phot.mag;em.UV.200-300nm double nullable max_delta_nuv_mag_limit Limit Flag for Maximum Absolute Delta Magnitude meta.code;src.var.amplitude;em.UV.200-300nm char nullable max_delta_nuv_mag Maximum Absolute Delta Magnitude mag src.var.amplitude;em.UV.200-300nm double nullable var_type Light Curve Type src.var char nullable broad_type Classification src.class char nullable "__x_ra_dec" System unit vector column double nullable "__y_ra_dec" System unit vector column double nullable "__z_ra_dec" System unit vector column double nullable "__row" System index column char nullable sf_years_limit Limit Flag for Structure Function on Years Timescale meta.code;src.var char nullable lii Galactic Longitude degree pos.galactic.lon double nullable xray_flag X-Ray Match meta.code;em.X-ray char nullable sf_days_limit Limit Flag for Structure Function on Days Timescale meta.code;src.var char nullable sigma_nuv_mag Intrinsic RMS Scatter mag stat.error;phot.mag;em.UV.200-300nm double nullable sigma_nuv_mag_limit Limit Flag for Intrinsic RMS Scatter meta.code;stat;phot.mag;em.UV.200-300nm char nullable host_redshift Redshift src.redshift double nullable class Browse Object Classification src.class short nullable host_morphology Optical Host Morphology src.morph char nullable host_color_class Optical Color Class src.class char nullable sf_days Structure Function on Days Timescale mag src.var double nullable bii Galactic Latitude degree pos.galactic.lat double nullable sf_years Structure Function on Years Timescale mag src.var double nullable