J/MNRAS/385/823ivo://CDS.VizieR/J/MNRAS/385/823doi:10.26093/cds/vizier.73850823CDSZheng Y.G.Zhang X.Bi X.W.Hao J.M.Zhang H.J.2024-07-06T20:15:54Z2009-05-30T09:33:32ZCDS support team

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

cds-question@unistra.frbl-lacertae-objectsinfrared-photometryvisible-astronomybroad-band-photometryBased on the long-term data in the literature, we present evidence for long-term optical spectral index variability behaviour for BL Lacertae object OJ 287. First we find that the optical spectral index variability period of BL Lacertae object OJ 287 is in agreement with the optical flux variability period of about 11.96yr. It is considered that different processes induce optical variability, and each process should have a definite signature in the spectral index, thus leading to the periodicity of the spectral index. We also find that the time lag between the optical spectral index and the optical flux density is half of the optical flux variability period. This result tends to support the argument that when the brightness of the long-term variations increases, the optical spectra become bluer. These variations can be explained by energy loss of the electrons during the outburst. We show that the spectral index is different during the flares compared with outside the flares; between the first and second flare peaks of the superflares, the spectrum shapes are different. Disparate processes possibly induce the two peaks of OJ 287.2008MNRAS.385..823Zhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/MNRAS/385/823CatalogResearchIsServedByTAP VizieR generic servicerelated-toJ/A+AS/129/569 : BVRI photometry of OJ 287 (Jia Guibin+ 1998)J/AJ/132/1256 : eim BATC photometry of OJ 287 (Wu+, 2006)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/MNRAS/385/823https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/MNRAS/385/823http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/MNRAS/385/823https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/MNRAS/385/823https://vizier.iucaa.in/viz-bin/votable?-source=J/MNRAS/385/823http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/MNRAS/385/823GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapOpticalInfrareddefaultJ/MNRAS/385/823/tables1Compiled raw data of OJ 287 (0851+202), magnitude valuesrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintJDJulian datedtime.epochintUmagU magnitudemagphot.mag;em.opt.Ufloate_Umag? rms uncertainty on Umagmagstat.error;phot.mag;em.opt.UfloatnullableBmagB magnitudemagphot.mag;em.opt.Bfloate_Bmag? rms uncertainty on Bmagmagstat.error;phot.mag;em.opt.BfloatnullableVmagV magnitudemagphot.mag;em.opt.Vfloate_Vmag? rms uncertainty on Vmagmagstat.error;phot.mag;em.opt.VfloatnullableRmag? R magnitudemagphot.mag;em.opt.Rfloatnullablee_Rmag? rms uncertainty on Rmagmagstat.error;phot.mag;em.opt.RfloatnullableImag? I magnitudemagphot.mag;em.opt.Ifloatnullablee_Imag? rms uncertainty on Imagmagstat.error;phot.mag;em.opt.IfloatnullableRefReference, in refs.dat filemeta.ref;pos.frame;meta.fileintJ/MNRAS/385/823/fluxCompiled raw data of OJ 287 (0851+202), flux density valuesrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintJDJulian datedtime.epochintUFluxFlux density in U bandmJyphot.flux;em.opt.Ufloate_UFlux? rms uncertainty on UFluxmJystat.errorfloatnullableBFluxFlux density in B bandmJyphot.flux;em.opt.Bfloate_BFlux? rms uncertainty on BFluxmJystat.errorfloatnullableVFluxFlux density in V bandmJyphot.flux;em.opt.Vfloate_VFlux? rms uncertainty on VFluxmJystat.errorfloatnullableRFlux? Flux density in R bandmJyphot.flux;em.opt.Rfloatnullablee_RFlux? rms uncertainty on RFluxmJystat.errorfloatnullableIFlux? Flux density in I bandmJyphot.flux;em.opt.Ifloatnullablee_IFlux? rms uncertainty on IFluxmJystat.errorfloatnullableRefReference, in refs.dat filemeta.ref;pos.frame;meta.fileintJ/MNRAS/385/823/refsReferencesrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintRefReference numbermeta.id;meta.mainintprimaryBibCodeBibCodemeta.bib.bibcodecharAutAuthor's namemeta.bib.authorcharComCommentsmeta.notechar