J/ApJS/225/29ivo://CDS.VizieR/J/ApJS/225/29doi:10.26093/cds/vizier.22250029CDSBon E.Zucker S.Netzer H.Marziani P.Bon N.Jovanovic P.,Shapovalova A.I.Komossa S.Gaskell C.M.Popovic L.C.Britzen S.,Chavushyan V.H.Burenkov A.N.Sergeev S.La Mura G.Valdes J.R.,Stalevski M.2017-06-02T08:37:13Z2016-11-16T07:23:02ZCDS support team

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

cds-question@unistra.frgalaxiesspectroscopyactive-galactic-nucleiWe present an analysis of 43 years (1972 to 2015) of spectroscopic observations of the Seyfert 1 galaxy NGC 5548. This includes 12 years of new unpublished observations (2003 to 2015). We compiled about 1600 H{beta} spectra and analyzed the long-term spectral variations of the 5100 A continuum and the H{beta} line. Our analysis is based on standard procedures, including the Lomb-Scargle method, which is known to be rather limited to such heterogeneous data sets, and a new method developed specifically for this project that is more robust and reveals a ~5700 day periodicity in the continuum light curve, the H{beta} light curve, and the radial velocity curve of the red wing of the H{beta} line. The data are consistent with orbital motion inside the broad emission line region of the source. We discuss several possible mechanisms that can explain this periodicity, including orbiting dusty and dust-free clouds, a binary black hole system, tidal disruption events, and the effect of an orbiting star periodically passing through an accretion disk.2016ApJS..225...29Bhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJS/225/29CatalogResearchIsServedByTAP VizieR generic servicerelated-toJ/ApJ/821/56 : Space telescope RM project III. NGC5548 LCs (Fausnaugh+, 2016)J/ApJS/222/25 : Long-term optical monitoring of E1821+643 (Shapovalova+, 2016)J/MNRAS/453/1562 : CRTS close supermassive black hole binaries (Graham+, 2015)J/ApJ/806/129 : Space telescope RM project. II. Swift data (Edelson+, 2015)J/ApJ/806/128 : Space telescope RM project. I. NGC5548 (De Rosa+, 2015)J/ApJ/806/22 : SEAMBHs IV. H{beta} time lags (Du+, 2015)J/ApJ/779/109 : Long-term monitoring of NGC 5548 (Peterson+, 2013)J/ApJS/201/23 : Spectroscopy of 88 z<0.7 SDSS QSOs (Eracleous+, 2012)J/ApJS/189/15 : FeII emission in a sample of AGN spectra (Kovacevic+, 2010)J/ApJ/683/L115 : Intermediate-line region in quasars (Hu+, 2008)J/A+A/422/925 : Profile variability in lines of NGC 5548 (Shapovalova+ 2004)J/ApJ/599/886 : Emission lines of radio-loud AGN (Eracleous+, 2003)J/A+A/371/79 : NGC5548 UBVRI phot. and Halpha, Hbeta fluxes (Dietrich+, 2001)J/ApJ/510/659 : Size and Structure of AGN in NGC 5548 (Peterson+, 1999)J/AJ/116/102 : NGC 5548 BR photometry (Tyson+ 1998)http://www.astronomy.ohio-state.edu/~agnwatch/data.html :https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJS/225/29https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJS/225/29http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJS/225/29https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJS/225/29https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJS/225/29http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJS/225/29GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapOpticaldefaultJ/ApJS/225/29/table2Spectral parameters obtained from the best fitsrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintJDJulian Date; JD-2400000 (1)dtime.epochdoubleFHbeta[0.6/17.5] H_{beta}_ flux, in units of 10^-13^erg/s/cm2/{AA}1e-15W.m**-2.nm**-1phot.flux;arith.ratiofloate_FHbeta[0/7] FHbeta uncertainty1e-15W.m**-2.nm**-1stat.errorfloatF5100[1.2/16] Continuum flux measured at 510nm, in units of 10^-15^erg/s/cm^2^1e-18W.m**-2phot.fluxfloate_F5100[0/4] F5100 uncertainty1e-18W.m**-2stat.errorfloatB25[-9359/-2490] Width of the blue side of the broad line measured at 1/4 of intensity highkm/sspect.line.widthfloatR25[2393/9965] Width of the red side of the broad line measured at 1/4 of intensity highkm/sspect.line.widthfloatB50Width of the blue side of the broad line measured at 1/2 of intensity highkm/sspect.line.widthfloatR50Width of the red side of the broad line measured at 1/2 of intensity highkm/sspect.line.widthfloatB75Width of the blue side of the broad line measured at 3/4 of intensity highkm/sspect.line.widthfloatR75Width of the red side of the broad line measured at 3/4 of intensity highkm/sspect.line.widthfloatB90[-6123/1440] Width of the blue side of the broad line measured at 9/10 of intensity highkm/sspect.line.widthfloatR90[-3545/3885] Width of the red side of the broad line measured at 9/10 of intensity highkm/sspect.line.widthfloatJ/ApJS/225/29/table1Log of the new spectroscopical observations 2003-2015 from SAO, INOAE and AsiagorecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintSeqRunning sequence number of the observationmeta.numberintDateUT date of the observationtime.epoch;obsnullableJDJulian date; JD-2400000dtime.epochdoubleObsA code assigned to the observatory (1)meta.code;instr.obstycharAp1Aperture used in the observations (Ap1xAp2)arcsecphys.angSize;instr.fovfloatAp2Aperture used in the observations (Ap1xAp2)arcsecphys.angSize;instr.fovfloatlambda1[3250/5800] Observed lower range of spectral domain0.1nminstr.bandwidth;stat.minintlambda2[6950/8120] Observed upper range of spectral domain0.1nminstr.bandwidth;stat.maxintSeeing[1.2/7.5] Seeingarcsecinstr.obsty.seeingfloat