SIMBAD references

2004A&A...421..103V - Astronomy and Astrophysics, volume 421, 103-114 (2004/7-1)

The WEBT BL Lacertae Campaign 2001 and its extension. Optical light curves and colour analysis 1994-2002.

VILLATA M., RAITERI C.M., KURTANIDZE O.M., NIKOLASHVILI M.G., IBRAHIMOV M.A., PAPADAKIS I.E., TOSTI G., HROCH F., TAKALO L.O., SILLANPAEAE A., HAGEN-THORN V.A., LARIONOV V.M., SCHWARTZ R.D., BASLER J., BROWN L.F., BALONEK T.J., BENITEZ E., RAMIREZ A., SADUN A.C., BOLTWOOD P., CARINI M.T., BARNABY D., COLOMA J.M., ROS J.A., DAI B.Z., XIE G.Z., MATTOX J.R., RODRIGUEZ D., ASFANDIYAROV I.M., ATKERSON A., BEEM J.L., BLOOM S.D., CHANTURIYA S.M., CIPRINI S., CRAPANZANO S., DE DIEGO J.A., EFIMOVA N.V., GARDIOL D., GUERRA J.C., KAHHAROV B.B., KAPANADZE B.Z., KARTTUNEN H., KATO T., KIMERIDZE G.N., KUDRYAVTSEVA N.A., LAINELA M., LANTERI L., LARIONOVA E.G., MAESANO M., MARCHILI N., MASSONE G., MONROE T., MONTAGNI F., NESCI R., NILSSON K., NOBLE J.C., NUCCIARELLI G., OSTORERO L., PAPAMASTORAKIS J., PASANEN M., PETERS C.S., PURSIMO T., REIG P., RYLE W., SCLAVI S., SIGUA L.A., UEMURA M. and WILLS W.

Abstract (from CDS):

BL Lacertae has been the target of four observing campaigns by the Whole Earth Blazar Telescope (WEBT) collaboration. In this paper we present UBVRI light cur ves obtained by the WEBT from 1994 to 2002, including the last, extended BL Lac 2001 campaign . A total of about 7500 optical observations performed by 31 telescopes from Japan to Mexico have been collected, to be added to the ∼15600 observations of the BL L ac Campaign 2000. All these data allow one to follow the source optical emission behaviour with unprecedented detail. The analysis of the colour indices reveals that the flux variability can be inte rpreted in terms of two components: longer-term variations occurring on a few-day time s cale appear as mildly-chromatic events, while a strong bluer-when-brighter chromatism characterizes very fast (intraday) flares. By decoupling the two components, we quantify the degree of chromatism inferring that longer-term flux changes imply moving along a∼0.1 bluer-when-brighter slope in the B-R versus R plane; a steeper slope of ∼0.4 would distinguish the shorter-term va riations. This means that, when considering the long-term trend, the B-band flux level i s related to the R-band one according to a power law of index ∼1.1. Doppler factor variations on a ``convex" spectrum could be the mechanism account ing for both the long-term variations and their slight chromatism.

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Journal keyword(s): galaxies: active - galaxies: BL Lacertae objects: general - galaxies: jets - galaxies: quasars: general

Simbad objects: 5

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