학술논문
The WEBT BL LacertaeCampaign 2001 and its extension
Document Type
Article
Author
Villata, M.; Raiteri, C. M.; Kurtanidze, O. M.; Nikolashvili, M. G.; Ibrahimov, M. A.; Papadakis, I. E.; Tosti, G.; Hroch, F.; Takalo, L. O.; Sillanpää, A.; Hagen-Thorn, V. A.; Larionov, V. M.; Schwartz, R. D.; Basler, J.; Brown, L. F.; Balonek, T. J.; Benítez, E.; Ramírez, 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.; Wills, W.; Villata, M.; Raiteri, C. M.; Kurtanidze, O. M.; Nikolashvili, M. G.; Ibrahimov, M. A.; Papadakis, I. E.; Tosti, G.; Hroch, F.; Takalo, L. O.; Sillanpää, A.; Hagen-Thorn, V. A.; Larionov, V. M.; Schwartz, R. D.; Basler, J.; Brown, L. F.; Balonek, T. J.; Benítez, E.; Ramírez, 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.; Wills, W.
Source
Astronomy and Astrophysics; July 2004, Vol. 421 Issue: 1 p103-114, 12p
Subject
Language
ISSN
00046361; 14320746
Abstract
BL Lacertaehas been the target of four observing campaigns by the Whole Earth Blazar Telescope (WEBT) collaboration. In this paper we present ${\it UBVRI}$light curves 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 ~$15\,600$observations of the BL Lac 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 interpreted in terms of two components: longer-term variations occurring on a few-day time scale 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 Rplane; a steeper slope of ~$ 0.4$would distinguish the shorter-term variations. This means that, when considering the long-term trend, the B-band flux level is related to the R-band one according to a power law of index ~$ 1.1$. Doppler factor variations on a “convex" spectrum could be the mechanism accounting for both the long-term variations and their slight chromatism.