J/ApJ/746/54ivo://CDS.VizieR/J/ApJ/746/54doi:10.26093/cds/vizier.17460054CDSGibson R.R.Brandt W.N.2017-06-19T07:57:46Z2013-09-26T09:07:11ZCDS support team

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

cds-question@unistra.frx-ray-sourcesquasarsredshiftedWe analyze the X-ray variability of 264 Sloan Digital Sky Survey spectroscopic quasars using the Chandra public archive. This data set consists of quasars with spectroscopic redshifts out to z {approx} 5 and covers rest-frame timescales up to {Delta}t_sys_{approx} 2000 days, with three or more X-ray observations available for 82 quasars. It therefore samples longer timescales and higher luminosities than previous large-scale analyses of active galactic nucleus (AGN) variability. We find significant ( >~ 3{sigma}) variation in {approx}30% of the quasars overall; the fraction of sources with detected variability increases strongly with the number of available source counts up to {approx}70% for sources with >= 1000 counts per epoch. Assuming that the distribution of fractional variation is Gaussian, its standard deviation is {approx}16% on >~ 1 week timescales, which is not enough to explain the observed scatter in quasar X-ray-to-optical flux ratios as being due to variability alone. We find no evidence in our sample that quasars are more variable at higher redshifts (z > 2), as has been suggested in previous studies. Quasar X-ray spectra vary similarly to some local Seyfert AGNs in that they steepen as they brighten, with evidence for a constant, hard spectral component that is more prominent in fainter stages. We identify one highly variable Narrow Line Seyfert 1-type spectroscopic quasar in the Chandra Deep Field-North. We constrain the rate of kilosecond-timescale flares in the quasar population using {approx}8 months of total exposure and also constrain the distribution of variation amplitudes between exposures; extreme changes (>100%) are quite rare, while variation at the 25% level occurs in <25% of observations. [O III] {lambda}5007 {AA} emission may be stronger in sources with lower levels of X-ray variability; if confirmed, this would represent an additional link between small-scale (corona) and large-scale (narrow-line region) AGN properties.2012ApJ...746...54Ghttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/746/54CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toB/chandra : The Chandra Archive Log (CXC, 1999-2013)VII/252 : SDSS-DR5 quasar catalog (Schneider+, 2007)J/ApJS/201/10 : SDSS quasar catalog with Swift observations (Wu+, 2012)J/ApJ/726/20 : X-ray emission from quasars (Miller+, 2011)J/ApJ/690/644 : Properties of SDSS QSOs in the ChaMP (Green+, 2009)J/ApJ/692/758 : BAL QSOs in SDSS-DR5 (Gibson+, 2009)J/ApJS/183/17 : The SDSS DR5/XMM-Newton quasar survey (Young+, 2009)J/AJ/133/313 : AGN from RASS and SDSS DR5 (Anderson+, 2007)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/746/54https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/746/54http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/746/54https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/746/54https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/746/54http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/746/54GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/ApJ/746/54/table1 (Properties common to each source)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJ/746/54/table1?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/746/54/table1?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/746/54/table1?GETtext/xml+votable180.050000true1.5941667-0.07344440.0055555555555555566/4124 4125 4206 4790 4808 5044 5099 5469 5471 5587 5597 5731 5797 5817 5881 5985 6069 6073 6075 6090 6448 6536 6538 6539 7178 7241 7273 7323 7345 7424 8921 9052 9146 9147 9148 9150 9151 9168 9343 9428 9506 9747 9842 9997 10153 10154 10183 10193 10217 10501 10512 10513 10515 10516 10517 10518 10589 11027 11080 11194 11195 11252 11372 11424 11425 11428 11434 11467 11807 17239 17406 17502 17754 17755 17763 17766 17767 17769 17772 17773 17812 17840 18009 18089 18385 18791 18795 19033 19036 19432 25950 25981 26022 26037 26100 26209 26215 26298 26316 26990 27091 27096 27127 27247 27256 27258 27259 27382 27428 27515 27718 27719 27743 27756 27758 27767 27773 27862 27912 27913 27914 27921 27936 28172 28184 32500 450447.945783846626256e-19 7.945783846626256e-19https://cdsarc.cds.unistra.fr/viz-bin/moc/J/ApJ/746/54?format=asciiX-rayOpticaldefaultJ/ApJ/746/54/table1Properties common to each sourcerecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintSDSSSDSS name (HHMMSS.ss+DDMMSS.s; J2000)meta.id;meta.maincharprimaryz[0.086/4.976] Redshiftsrc.redshiftfloatNobs[2/24] Number of observationsmeta.numberintSSimbad column added by the CDSmeta.ref.urlcharRL[*/1] Known radio loud source (1)src.classcharBAL[0/1] Known broad absorption line (1=BAL quasar)src.classintF2500[0.107/22.112]? 2500{AA} flux density (2)mJyphot.flux.densityfloatnullableRate[-1.975/1481.93] Constant count ratecount.m**-2.s**-1phot.count;em.X-raydoublee_Rate[0.352/404.062] Rate uncertaintycount.m**-2.s**-1stat.errorfloatVar?[0/1] Variable source? (3)meta.code;src.varintRateHQ[-0.004/72.24]? Constant count rate in HQ sample (G1)count.m**-2.s**-1phot.count;em.X-rayfloatnullablee_RateHQ[0.035/3.077]? RateHQ uncertainty (G1)count.m**-2.s**-1stat.errorfloatnullableVarHQ?[0/1]? Variable source in HQ sample? (3)(G1)meta.code;src.varintnullableDR5Display the SDSS-DR5 quasar catalogs data (Cat. VII/252) for this quasarmeta.ref.urlcharSimbadSimbad column added by the CDSmeta.refcharNEDSimbad column added by the CDSmeta.refchar_RAPositions from SDSS names (right ascension part)degpos.eq.ra;meta.main_DEPositions from SDSS names (declination part)degpos.eq.dec;meta.mainJ/ApJ/746/54/XobsX-ray observations of each source: count rates, total counts, counts in each bandE_LumUpper limit uncertainty in Lum1e+35Wstat.error;stat.maxdoublee_LumLower limit uncertainty in Lum1e+35Wstat.errordoublerecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintSDSSSDSS Name (HHMMSS.ss+DDMMSS.s; J2000)meta.id;meta.maincharObsId[304/9880] Observation numbermeta.id;obsintExp[161/170433] Exposure timestime.duration;obs.exposuredoubleOA[0.08/14.88] Off-Axis Anglearcmininstr.offsetfloatHQ?[0/1] In HQ sample flag (1=yes) (G1)meta.codeintTSTARTChandra TSTART parameter (1)stime.epochdoubleCRate[-5/1600] Source count rate (in units of 10^-6^ct/cm^2^/s)0.01m**-2.s**-1phot.count;em.X-rayfloatE_CRateUpper limit uncertainty on CRate0.01m**-2.s**-1stat.error;stat.maxfloate_CRateLower limit uncertainty on CRate0.01m**-2.s**-1stat.errorfloatCtLum[-237/3533] Count luminosity1e+52count.s**-1phys.luminosity;em.X-rayfloatE_CtLumUpper limit uncertainty on CtLum1e+52count.s**-1stat.error;stat.maxfloate_CtLumLower limit uncertainty on CtLum1e+52count.s**-1stat.errorfloatFull[0/33089] Full (0.5-8 keV) band total counts (2)ctphot.count;em.X-raydoubleE_FullUpper limit uncertainty on Fullctstat.error;stat.maxfloate_FullLower limit uncertainty on Fullctstat.errorfloatSoft[0/24936] Soft (0.5-2 keV) band total countsctphot.count;em.X-raydoubleE_SoftUpper limit uncertainty on Softctstat.error;stat.maxfloate_SoftLower limit uncertainty on Softctstat.errorfloatHard[0/8337] Hard (2-8 keV) band total countsctphot.count;em.X-raydoubleE_HardUpper limit uncertainty on Hardctstat.error;stat.maxfloate_HardLower limit uncertainty on Hardctstat.errorfloatSFcts[-6.3/33089] Source full (0.5-8keV) band counts (1)ctphot.count;em.X-raydoubleE_SFctsUpper limit uncertainty in SFctsctstat.error;stat.maxfloate_SFctsLower limit uncertainty on SFctsctstat.errorfloatSScts[-3.7/24936] Source soft (0.5-2 keV) band countsctphot.count;em.X-raydoubleE_SSctsUpper limit uncertainty on SSctsctstat.error;stat.maxfloate_SSctsLower limit uncertainty on SFctsctstat.errorfloatSHcts[-8.6/8337] Source hard (2-8 keV) band countsctphot.count;em.X-raydoubleE_SHctsUpper limit uncertainty on SHctsctstat.error;stat.maxfloate_SHctsLower limit uncertainty on SHctsctstat.errorfloatbgFcts[-0.4/428] Background full (0.5-8 keV) band counts (1)ctinstr.backgroundfloatE_bgFctsUpper limit uncertainty in bgFctsctstat.error;stat.maxfloate_bgFctsLower limit uncertainty in bgFctsctstat.errorfloatbgScts[-0.4/75] Background soft (0.5-2 keV) band counts (1)ctinstr.background;em.X-ray.softfloatE_bgSctsUpper limit uncertainty in bgSctsctstat.error;stat.maxfloate_bgSctsLower limit uncertainty in bgSctsctstat.errorfloatbgHcts[-0.3/356] Background hard (2-8 keV) band counts (1)ctinstr.background;em.X-ray.hardfloatE_bgHctsUpper limit uncertainty in bgHctsctstat.error;stat.maxfloate_bgHctsLower limit uncertainty in bgHctsctstat.errorfloatHR[-1/1]? Hardness ratio (2)phot.flux;arith.ratiofloatnullableE_HR? Upper limit uncertainty on HRstat.error;stat.maxfloatnullablee_HR? Lower limit uncertainty on HRstat.errorfloatnullableLum[-3900/58166] Approximate 0.5-8keV luminosity (3)1e+35Wphys.luminosity;em.X-raydoubleJ/ApJ/746/54/table4Spectral model consisting of a Galactic-absorbed power law absorbed by one absorption edgerecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintSDSSSDSS name (HHMMSS.ss+DDMMSS.s; J2000)meta.id;meta.maincharObsId[580/9876] Observation ID numbermeta.id;obsintNorm[1.17/44.1] Normalization at 1keV in units of 10^-5^photon/keV/cm^2^/sstat.fit.paramfloatE_Norm[0.0616/2.47] Positive uncertainty on Normstat.error;stat.maxfloate_Norm[0.0553/1.71] Negative uncertainty on Normstat.errorfloatGamma[0.087/2.899] Photon index {Gamma}meta.code;spect.indexfloatE_Gamma[0.024/0.354] Positive uncertainty on Gammastat.error;stat.maxfloate_Gamma[0.024/0.222] Negative uncertainty on Gammastat.errorfloattau[0/3.431] Edge optical depth ({tau})phys.absorption.opticalDepthfloatE_tau[0.014/3.163] Positive uncertainty on taustat.error;stat.maxfloate_tau[0/1.837] Negative uncertainty on taustat.errorfloat