J/A+A/369/758ivo://CDS.VizieR/J/A+A/369/758doi:10.26093/cds/vizier.33690758CDSFan J.H.Qian B.C.Tao J.2001-04-21T07:41:58Z2001-04-21T07:41:54ZCDS support team

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

cds-question@unistra.frbl-lacertae-objectsinfrared-photometryvisible-astronomyphotometryWe present the optical (V, R, and I) photometry for BL Lacertae, which was observed from 1997 through 1999, with the 1.56-m telescope at the Shanghai astronomical observatory (SHAO). After the 1997 outburst, it dimmed to a low state and then brightened again. During the period JD 2450701 to JD 2450701.5, variations of 0.40mag, 0.27mag, and 0.21mag over a time scale of 100min were found for V, R, and I bands, suggesting that the variations were decreasing with wavelength. The correlation between V, R, and I is also analyzed using the DCF (Discrete Correlation Function) method. This shows that the variability in the V, R, and I bands are correlated with no time delay longer than 0.2day.2001A&A...369..758Fhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/369/758CatalogResearchIsServedByTAP VizieR generic servicerelated-toJ/A+AS/143/357 : Tuorla Quasar Monitoring (Katajainen+ 2000)J/A+AS/136/455 : BVRI photometry of 3 BL Lac objects (Bai+, 1999)J/A+AS/120/89 : 408MHz observations (Bondi+ 1996)J/AZh/71/717 : Polarimetric Observations of BL Lac (Gagen-Torn+ 1994)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/369/758https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/369/758http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/369/758https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/369/758https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/369/758http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/369/758GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapOpticalInfrareddefaultJ/A+A/369/758/table1Optical measurements of BL Lacertae in 1997-1999recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintHJDHeliocentric Julian datedtime.epochdoubleVmag? V magnitudemagphot.mag;em.opt.Vfloatnullablee_Vmag? rms uncertainty in Vmagmagstat.errorfloatnullableRmag? R magnitudemagphot.mag;em.opt.Rfloatnullablee_Rmag? rms uncertainty in Rmagmagstat.errorfloatnullableImag? I magnitudemagphot.mag;em.opt.Ifloatnullablee_Imag? rms uncertainty in Imagmagstat.errorfloatnullable