J/ApJS/238/25ivo://CDS.VizieR/J/ApJS/238/25doi:10.26093/cds/vizier.22380025CDSde la Vega A.Bianchi L.2019-03-27T06:26:48Z2019-01-24T14:29:06ZCDS support team

CDS, Observatoire de Strasbourg, 11 rue de l'Universite, F-67000 Strasbourg, France

cds-question@unistra.frultraviolet-photometryastronomical-object-identificationvariable-starsIn order to develop and test a methodology to search for UV variability over the entire Galaxy Evolution Explorer (GALEX) database down to the shortest timescales, we analyzed time-domain photometry of ~5000 light curves of ~300 bright (mFUV, mNUV<=14) and blue (mFUV-mNUV<0) GALEX sources. Using the gPhoton database tool, we discovered and characterized instrumentally induced variabilities in time-resolved GALEX photometry that may severely impact automated searches for short-period variations. The most notable artifact is a quasi-sinusoidal variation mimicking light curves typical of pulsators, seen occasionally in either one or both detectors, with amplitudes of up to 0.3mag and periods corresponding to the periodicity of the spiral dithering pattern used during the observation (P~120s). Therefore, the artifact may arise from small-scale response variations. Other artifacts include visit-long "sagging" or "hump" in flux, occurring when the dithering pattern is not a spiral, or a one-time change in flux level during the exposure. These instrumentally caused variations were not reported before, and are not due to known (and flagged) artifacts such as hotspots, which can be easily eliminated. To characterize the frequency and causality of such artifacts, we apply Fourier transform analysis to both light curves and dithering patterns, and examine whether artificial brightness variations correlate with visit or instrumental parameters. Artifacts do not correlate with source position on the detector. We suggest methods to identify artifact variations and to correct them when possible.2018ApJS..238...25Dhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJS/238/25CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toII/312 : GALEX-DR5 (GR5) sources from AIS and MIS (Bianchi+ 2011)II/335 : Revised catalog of GALEX UV sources (GUVcat_AIS GR6+7) (Bianchi+ 2017)J/ApJS/173/673 : M dwarf UV flares in GALEX (Welsh+, 2007)J/AJ/136/259 : Second GALEX UV variability catalog (GUVV-2) (Wheatley+, 2008)J/ApJ/766/60 : GALEX Time Domain Survey I. UV variable sources (Gezari+, 2013)J/ApJ/845/171 : Rapidly pulsating sdB stars with GALEX (Boudreaux+, 2017)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJS/238/25https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJS/238/25http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJS/238/25https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJS/238/25https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJS/238/25http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJS/238/25GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/ApJS/238/25/table1 (The sources of the GALEX (GR6+7) merged catalog (MCAT) culled sample)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJS/238/25/table1?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJS/238/25/table1?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJS/238/25/table1?GETtext/xml+votable180.050000true17.73122-51.844021110.0055555555555555566/0 226 404 437 548 550 560 764 1065 1519 1679 1682 2094 2188 2203 2243 2282 2623 2640 2642 2670 2681 2712 2715 2736 2741 2765 2767 2879 2987 2988 4011 4012 4099 4122 4123 4135 4163 4164 4188 4195 4233 4245 4377 4658 4700 4727 4772 4790 4859 4898 4902 5281 5634 5818 6070 6113 6174 6210 6246 6612 6949 7302 7361 7532 7980 9336 9433 9512 9633 9640 9842 9954 9981 9995 10017 10097 10144 10159 10214 10233 10378 10379 10400 10799 11598 11605 11642 12377 12511 12577 12642 13336 13629 14149 14151 14158 14162 14587 14773 14966 14976 15108 15134 15141 15351 15949 16016 16404 16550 16672 16744 17301 17318 17343 17386 17579 17865 18008 18031 18222 18391 18652 18705 18716 18766 18774 18798 18966 18987 18990 19002 19032 19033 19067 19073 19085 19098 19115 19121 19145 19147 19323 19419 19666 19683 19726 19863 19906 20657 21010 21326 21849 21967 22009 22011 22352 22364 22379 23101 23103 23145 23398 23476 23518 23544 23545 24044 24047 24056 24063 24270 24292 24843 25318 25324 25344 25585 25742 25915 25921 25927 25934 25939 25953 25957 25972 26006 26106 26310 26351 26799 26808 26959 26969 26993 27000 27045 27227 27247 27259 27289 27308 27312 27324 27344 27369 27434 27459 27464 27734 27859 27905 27911 28221 28637 29003 29219 29381 30376 31419 31437 31444 31689 31846 31880 31991 32189 32191 32231 32523 32537 32629 32674 32680 32954 32956 33104 33117 33287 33589 33629 33641 34554 34635 34810 34975 35014 35383 35715 35720 35959 36437 36668 36679 36726 37113 38784 38799 38841 39960 40279 40323 40902 40910 40944 40948 40957 43734 44671 45305 45367 45757 46178 47001 47002 47458 47629 47828 47935 48500 48665 48698 49130https://cdsarc.cds.unistra.fr/viz-bin/moc/J/ApJS/238/25?format=asciiUVdefaultJ/ApJS/238/25/table1The sources of the GALEX (GR6+7) merged catalog (MCAT) culled samplerecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintobjidGALEX objid identifiermeta.id;meta.mainRAJ2000Right Ascension in decimal degrees (J2000)degpos.eq.ra;meta.mainDEJ2000Declination in decimal degrees (J2000)degpos.eq.dec;meta.mainFUVmag[10.6/14] Apparent FUV band AB magnitudemagphot.mag;em.UVfloate_FUVmag[0/0.004] Uncertainty in FUVmagmagstat.error;phot.mag;em.UV.100-200nmfloatNUVmag[10.8/14] Apparent NUV band AB magnitudemagphot.mag;em.UVfloate_NUVmag[0/0.003] Uncertainty in NUVmagmagstat.error;phot.mag;em.UV.200-300nmfloatFUVexp[502/67899] Total FUV band exposure timestime.duration;obs.exposure;em.UV.100-200nmdoubleNUVexp[502/77766] Total NUV band exposure timestime.duration;obs.exposure;em.UV.200-300nmdoublenFUV[1/132] Number of FUV band visitsmeta.numberintnNUV[1/170] Number of NUV band visitsmeta.numberintIDSIMBAD identifiermeta.id.crosschardelFUV[0/9.5]? Total FUV band magnitude change (1)magsrc.var.amplitudefloatnullabledelNUV[0/2.1]? Total NUV band magnitude change (1)magsrc.var.amplitudefloatnullableAISDisplay the GALEX GR6+7 AIS data (II/335) within 3"meta.ref.urlintnullable