J/ApJS/222/25ivo://CDS.VizieR/J/ApJS/222/25doi:10.26093/cds/vizier.22220025CDSShapovalova A.I.Popovic L.C.Chavushyan V.H.Burenkov A.N.Ilic D.,Kollatschny W.Kovacevic A.Valdes J.R.Patino-Alvarez V.,Leon-Tavares J.Torrealba J.Zhdanova V.E.2017-07-05T06:59:33Z2016-04-04T15:48:40ZCDS support team

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

cds-question@unistra.frquasarsspectroscopyinfrared-photometryvisible-astronomybroad-band-photometryWe report the results of the first long-term (1990-2014) optical spectrophotometric monitoring of a binary black hole candidate QSO E1821+643, a low-redshift, high-luminosity, radio-quiet quasar. In the monitored period, the continua and H{gamma} fluxes changed about two times, while the H{beta} flux changed about 1.4 times. We found periodical variations in the photometric flux with periods of 1200, 1850, and 4000 days, and 4500-day periodicity in the spectroscopic variations. However, the periodicity of 4000-4500 days covers only one cycle of variation and should be confirmed with a longer monitoring campaign. There is an indication of the period around 1300 days in the spectroscopic light curves, but with small significance level, while the 1850-day period could not be clearly identified in the spectroscopic light curves. The line profiles have not significantly changed, showing an important red asymmetry and broad line peak redshifted around +1000km/s. However, H{beta} shows a broader mean profile and has a larger time lag ({tau}~120 days) than H{gamma} ({tau}~60 days). We estimate that the mass of the black hole is ~2.6x10^9^M_{sun}_. The obtained results are discussed in the frame of the binary black hole hypothesis. To explain the periodicity in the flux variability and high redshift of the broad lines, we discuss a scenario where dense, gas-rich, cloudy-like structures are orbiting around a recoiling black hole.2016ApJS..222...25Shttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJS/222/25CatalogResearchIsServedByTAP VizieR generic servicerelated-toJ/A+A/583/A75 : Large Quasar Astrometric Catalogue 3 (LQAC-3) (Souchay+, 2015)J/A+A/573/A101 : Generalised Lomb-Scargle periodogram code (Mortier+, 2015)J/MNRAS/445/2061 : Absorption in circumgalactic medium (Liang+, 2014)J/A+A/559/A10 : Arp 102B spectral optical monitoring (Shapovalova+, 2013)J/ApJS/189/15 : FeII emission in a sample of AGN spectra (Kovacevic+, 2010)J/ApJ/716/993 : LAMP: reverberation mapping of H and He lines (Bentz+, 2010)J/ApJ/702/1353 : H{beta} and V-band light curves of NGC 4051 (Denney+, 2009)J/ApJ/698/895 : Variations in QSOs optical flux (Kelly+, 2009)J/AJ/138/845 : BVRI observations of 235 bright quasars (Ojha+, 2009)J/A+A/422/925 : Profile variability in lines of NGC 5548 (Shapovalova+ 2004)J/A+A/412/707 : Absorption-line systems in QSO spectra (Ryabinkov+, 2003)J/ApJS/143/257 : AGN emission line properties (Kuraszkiewicz+, 2002)J/A+A/376/775 : UBVRI and H-beta observations of 3C 390.3 (Shapovalova+ 2001)J/ApJS/97/1 : HST Quasar Absorption Line Key Project. X. (Lockman+ 1995)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJS/222/25https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJS/222/25http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJS/222/25https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJS/222/25https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJS/222/25http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJS/222/25GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tap2.762881831355591e-19 4.920466254354166e-19InfraredOpticaldefaultJ/ApJS/222/25/table3Log of spectroscopic observationsrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintSeqSpectroscopic Observation Running Numbermeta.id;meta.mainintDateUT observation datetime.epoch;obsnullableJDModified Julian Date, JD-2400000dtime.epochfloatCodeSpectroscopic Observation Code (1)meta.id;obscharApXProjected spectrograph entrance aperture in Xarcsecinstr.fovfloatApYProjected spectrograph entrance aperture in Yarcsecinstr.fovfloatSpmin[3700/6060] Spectral Range, minimum in Angstroms0.1nmem.wlintSpmax[6630/7690] Spectral Range, maximum in Angstroms0.1nmem.wlintSeeing[1/5.5]? Mean Spectroscopic Observation Seeingarcsecinstr.obsty.seeing;obs;stat.meanfloatnullableB_Seeing[2.5]? Spectroscopic Observation Seeing, Maximumarcsecinstr.obsty.seeing;obsfloatnullableJ/ApJS/222/25/table1The measured photometric magnitudesrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintSeqPhotometric Observation Running Numbermeta.id;meta.mainintDateUT observation datetime.epoch;obsnullableJDModified Julian Date, JD-2400000dtime.epochfloatSeeing[1/4.1] Mean Photometric Observation Seeingarcsecinstr.obsty.seeing;obs;stat.meanfloatRmag[13.4/14]? R band magnitudemagphot.mag;em.opt.Rfloatnullablee_Rmag[0.009/0.04]? Uncertainty in Rmagmagstat.error;phot.mag;em.opt.RfloatnullableVmag[14.6/15.3] V band magnitudemagphot.mag;em.opt.Vfloate_Vmag[0.008/0.04] Uncertainty in Vmagmagstat.error;phot.mag;em.opt.VfloatBmag[13.7/14.6] B band magnitudemagphot.mag;em.opt.Bfloate_Bmag[0.009/0.04] Uncertainty in Bmagmagstat.error;phot.mag;em.opt.BfloatJ/ApJS/222/25/table7Measured broad-line and line-segment fluxes of H{beta}recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintSeqSpectroscopic Observation Running Numbermeta.id;meta.mainintJDModified Julian Date, JD-2400000dtime.epochfloatHb-broad[6.4/11.3] Flux of broad H{beta}, total line1e-13mW.m**-2phot.fluxfloate_Hb-broad[0.1/0.4] Uncertainty in Hb-broad1e-13mW.m**-2stat.errorfloatHb-blue[0.6/1.2] Flux of broad H{beta} line-segments, blue1e-13mW.m**-2phot.fluxfloate_Hb-blueUncertainty in Hb-blue1e-13mW.m**-2stat.errorfloatHb-core[3.2/5.9] Flux of broad H{beta} line-segments, core1e-13mW.m**-2phot.fluxfloate_Hb-coreUncertainty in Hb-core1e-13mW.m**-2stat.errorfloatHb-red[1.5/3] Flux of broad H{beta} line-segments, red1e-13mW.m**-2phot.fluxfloate_Hb-redUncertainty in Hb-red1e-13mW.m**-2stat.errorfloatHb-far[0.5/1.2] Flux of broad H{beta} line-segments, far red1e-13mW.m**-2phot.fluxfloate_Hb-farUncertainty in Hb-far1e-13mW.m**-2stat.errorfloatJ/ApJS/222/25/table5Measured line and continuum fluxesrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintSeqSpectroscopic Observation Running Numbermeta.id;meta.mainintDateUT observation datetime.epoch;obsnullableJDModified Julian Date, JD-2400000dtime.epochfloatF(5100)[4.9/10.7] Continuum flux at 5100{AA}, rest frame, in 10-15erg/cm2/s/A1e-17W.m**-2.nm**-1phot.fluxfloate_F(5100)[0.1/0.3] Uncertainty in F(5100), in 10-15erg/cm2/s/A1e-17W.m**-2.nm**-1stat.errorfloatHbeta[10.8/15.2] H{beta} line flux, in 10-13erg/cm2/s1e-16W.m**-2phot.flux;em.line.Hbeta;spect.linefloate_Hbeta[0.3/0.5] Uncertainty in Hbeta, in 10-13erg/cm2/s1e-16W.m**-2stat.errorfloatF(4200)[6.5/14]? Continuum flux at 4200{AA}, rest frame, in 10-15 erg/cm2/s/A1e-17W.m**-2.nm**-1phot.fluxfloatnullablee_F(4200)[0.2/0.5]? Uncertainty in F(4200), in 10-15 erg/cm2/s/A1e-17W.m**-2.nm**-1stat.errorfloatnullableHgamma[1.9/4.2]? H{gamma} line flux, in 10-13erg/cm2/s1e-16W.m**-2phot.flux;em.line.Hgamma;spect.linefloatnullablee_Hgamma[0.1/0.3]? Uncertainty in Hgamma, in 10-13erg/cm2/s1e-16W.m**-2stat.errorfloatnullable