J/A+AS/136/455ivo://CDS.VizieR/J/A+AS/136/455CDSBai J.MXie G.Z.Li K.H.Zhang X.Liu W.W.1999-05-14T12:59:02Z1999-05-14T12:58:21ZCDS support team

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

cds-question@unistra.frbl-lacertae-objectsinfrared-photometryvisible-astronomyWide-band photometryThe results of optical photometric (BVRI) monitoring of three BL Lac objects over a time interval of about four years are presented. The sources are three classical radio-selected BL Lac objects, BL Lac, OJ 287 and PKS 0735+178. During our observation OJ 287 was in the stage of a large periodic outburst which consisted of at least two peaks. Almost all the observations obtained over consecutive nights detected intranight variations. In 1995 and 1996 BL Lac kept in faint states, with fewer and smaller rapid flares and fluctuations. On the contrary, in late 1997 BL Lac was at the stage of a large outburst, accompanied with much more large amplitude rapid flares and fluctuations. PKS 0735+178 was almost at its faint end from 1994 to early 1998. Over this time interval, the intraday variations and microvariations in PKS 0735+178 were rare and the amplitude was very small, except a rapid darkening of ~0.4mag on 24 January 1995. Previous work by Webb et al. (1988AJ.....95..374W), Wagner et al. (1996AJ....111.2187W) and Pian et al. (1997ApJ...486..784P) also showed the same behaviour of variability as BL Lac and PKS 0735+178 in BL Lac, S5 0716+714, PKS 2155-304, respectively. We propose that the motion of orientation of the relativistic jet in a BL Lac object be responsible for these variability behaviours.1999A&AS..136..455Bhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+AS/136/455CatalogResearchIsServedByTAP VizieR generic servicerelated-toJ/A+AS/98/393 : 1Jy BL Lac Objects: Observational Data (Stickel+ 1993)J/A+AS/106/361 : CCD Photometry of BL Lac objects (Xie+ 1994)J/AZh/71/717 : Polarimetric Observations of BL Lac (Gagen-Torn+ 1994)J/AJ/104/28 : JHKL photometry of BL Lac Objects (Bersanelli+ 1992)J/A+AS/116/403 : VRI photometry of stars in 12 BL Lac objects (Fiorucci+, 1996)J/A+AS/132/361 : Optical observations of eight BL Lacs (Raiteri+ 1998)J/A+AS/132/83 : BVRI photometry of 7 BL Lac objects (Bai+ 1998)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+AS/136/455https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+AS/136/455http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+AS/136/455https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+AS/136/455https://vizier.iucaa.in/viz-bin/votable?-source=J/A+AS/136/455http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+AS/136/455GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapOpticalInfrareddefaultJ/A+AS/136/455/table1Photometric data of three BL Lac objectsrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintDateObservation datetime.epochnullableJDJulian Datedtime.epochdoublemagMagnitudemagphot.magfloate_magrms uncertainty on magmagstat.errorfloatBand[BVRI] Filter used for the magnitudemeta.code;instr.filtercharObjectName of the object observedmeta.id;meta.mainchar