J/ApJS/241/33ivo://CDS.VizieR/J/ApJS/241/33doi:10.26093/cds/vizier.22410033CDSLi Y.-R.Wang J.-M.Zhang Z.-X.Wang K.Huang Y.-K.Lu K.-X.Hu C.,Du P.Bon E.Ho L.C.Bai J.-M.Bian W.-H.Yuan Y.-F.Winkler H.,Denissyuk E.K.Valiullin R.R.Bon N.Popovic L.C.2020-04-08T13:13:10Z2019-12-31T15:14:08ZCDS support team

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

cds-question@unistra.fractive-galactic-nucleivisible-astronomyspectroscopyWe study the long-term variability in the optical monitoring database of Ark 120, a nearby radio-quiet active galactic nucleus (AGN) at a distance of 143Mpc (z=0.03271). We compiled the historical archival photometric and spectroscopic data since 1974 and conducted a new two-year monitoring campaign in 2015-2017, resulting in a total temporal baseline over four decades. The long-term variations in the optical continuum exhibit a wave-like pattern and the H{beta} integrated flux series varies with a similar behavior. The broad H{beta} profiles have asymmetric double peaks, which change strongly with time and tend to merge into a single peak during some epochs. The period in the optical continuum determined from various period-search methods is about 20yr, and the estimated false alarm probability with null hypothesis simulations is about 1x10^-3^. The overall variations of the broad H{beta} profiles also follow the same period. However, the present database only covers two cycles of the suggested period, which strongly encourages continued monitoring to track more cycles and confirm the periodicity. Nevertheless, in light of the possible periodicity and the complicated H{beta} profile, Ark 120 is one candidate of the nearest radio-quiet AGNs with possible periodic variability, and it is thereby a potential candidate host for a sub-parsec supermassive black hole binary.2019ApJS..241...33Lhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJS/241/33CatalogResearchIsServedByTAP VizieR generic servicerelated-toIII/218 : ELODIE archive (Prugniel+, 2001)VII/259 : 6dF galaxy survey final redshift release (Jones+, 2009)J/PASP/111/438 : Updated Zwicky catalog (UZC) (Falco+, 1999)J/ApJ/622/129 : Lag-luminosity relationship in AGN (Sergeev+, 2005)J/ApJ/696/870 : Catalina Real-time Transient Survey (CRTS) (Drake+, 2009)J/ApJ/698/895 : Variations in QSOs optical flux (Kelly+, 2009)J/ApJS/189/15 : FeII emission in a sample of AGN spectra (Kovacevic+, 2010)J/ApJ/730/19 : IR spectra & SEDs for starbursts and AGNs (Sargsyan+, 2011)J/ApJ/753/L2 : Reverberation mapping of AGNs (Assef+, 2012)J/ApJ/779/109 : Long-term monitoring of NGC 5548 (Peterson+, 2013)J/ApJ/782/45 : SEAMBHs. I. Mrk 142, Mrk 335 & IRAS F12397+3333 (Du+, 2014)J/ApJ/788/159 : 17 Seyfert 1 galaxies light curves (Koshida+, 2014)J/ApJ/788/48 : X-ray through NIR photometry of NGC 2617 (Shappee+, 2014)J/MNRAS/453/1562 : CRTS close supermassive black hole binaries (Graham+, 2015)J/ApJS/225/29 : NGC 5548 43 year-long monitoring in H{beta} (Bon+, 2016)J/ApJ/818/L14 : RM AGNs accretion rates and BH masses (Du+, 2016)J/ApJ/825/126 : SEAMBHs. V. The third year (Du+, 2016)J/ApJ/869/142 : Monitoring AGNs with H{beta} Asymmetry (MAHA). (Du+, 2018)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJS/241/33https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJS/241/33http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJS/241/33https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJS/241/33https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJS/241/33http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJS/241/33GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapOpticaldefaultJ/ApJS/241/33/table4The centroid wavelength and dispersion data of the broad H{beta} linerecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintJD[43104.5/57748.3] Julian Date; JD-2400000dtime.epochdoublelamHb[4860.17/4881.89] Centroid wavelength, broad H{beta} line; in Angstrom units0.1nmem.wl;spect.linefloatsigHb[24.97/46.95] Dispersion, broad H{beta} line; in Angstrom units0.1nmspect.line.widthfloatJ/ApJS/241/33/table1Data sets for the light curves of Ark 120recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintn_Setp: photometric data at the V-band, except for M79 at M-band; or s: spectroscopymeta.notecharSetDataset IDmeta.id;meta.dataset;meta.maincharprimaryf_SetFlag on Set (1)meta.codecharRef[1/15] Reference (2)meta.ref;pos.frameintJDlJulian Date of observation, startdtime.epochintJDuJulian Date of observation, enddtime.epochintDatelYear of observation, startyrtime.epochintDateuYear of observation, endyrtime.epochintNobs[20/476] Number of observationsmeta.numberintApAperturearcsecphys.angSize;instr.fovcharFOIII[0.7/1.4]? Flux of [OIII]{lambda}5007 used for absolute calibration of spectra in the data set; in 10^-13^erg/s/cm^2^1e-16W.m**-2phot.fluxfloatnullablephi[0.3/1.2]? Scale factor {phi} (3)arith.factorfloatnullablee_phi[0.003/0.3]? {phi} uncertaintystat.errorfloatnullableG[-8.1/6.6]? Flux adjustment (G); in 10^-15^erg/s/cm^2/{AA} units (3)1e-17W.m**-2.nm**-1arith.factorfloatnullablee_G[0.03/1.1]? G uncertainty1e-17W.m**-2.nm**-1stat.errorfloatnullableNlcNumber of optical LC measurements for this DataSet (link to Table 3)meta.numberintnullableJ/ApJS/241/33/table3Compiled optical light curve of Ark 120recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintJD[42392/58451.1] Julian Date; JD-2400000dtime.epochdoubleF5100[3.9/19.8] Flux density at 5100{AA}; in 10^-15^erg/s/cm^2/{AA} units1e-17W.m**-2.nm**-1phot.fluxfloate_F5100[0.07/3.1] Uncertainty in F51001e-17W.m**-2.nm**-1stat.errorfloatSetDataset (as in Table 1)meta.id;meta.datasetchar