The WEBT BL Lacertae Campaign 2001 and its extension Optical light curves and colour analysis 1994-2002
M. VillataNational Institute for Astrophysics, Rome, ItalyC. M. RaiteriNational Institute for Astrophysics, Rome, ItalyO. M. KurtanidzeAbastumani Astrophysical Observatory, Tbilisi, GeorgiaM. G. NikolashviliAbastumani Astrophysical Observatory, Tbilisi, GeorgiaM. IbrahimovAcademy of Sciences Republic of Uzbekistan, Tashkent, UzbekistanJ. L. BeemUniversity of Crete, Rethymno, GreeceI. E. PapadakisIESL, FORTH, 711 10 Heraklion, Crete, GreeceG. TostiDipartimento di Fisica, Università di Perugia, Via A. Pascoli, 06123 Perugia, ItalyS. D. BloomUniversity of Perugia, Perugia, ItalyS. M. ChanturiyaMasaryk University, Brno, CzechiaFilip HrochInstitute of Theoretical Physics and Astrophysics, Faculty of Science, Masaryk University, Kotlářská 2, 611 37 Brno, Czech RepublicS. CipriniDipartimento di Fisica, Università di Perugia, Via A. Pascoli, 06123 Perugia, ItalyL. O. TakaloS. CrapanzanoIstituto Nazionale di Astrofisica (INAF), Osservatorio Astronomico di Torino, via Osservatorio 20, 10025 Pino Torinese (TO), ItalyA. SillanpääV. A. Hagen‐ThornAstronomical Institute, St.-Petersburg State University, Universitetsky Pr. 28, Petrodvoretz, 198504 St.-Petersburg, RussiaJ. A. de DiegoSt Petersburg University, Saint Petersburg, RussiaV. M. LarionovAstronomical Institute, St.-Petersburg State University, Universitetsky Pr. 28, Petrodvoretz, 198504 St.-Petersburg, RussiaН. В. ЕфимоваSt Petersburg University, Saint Petersburg, RussiaRichard D. SchwartzDepartment of Physics and Astronomy, University of Missouri-St. Louis, 8001 Natural Bridge Road, St. Louis, MO 63121, USAD. GardiolUniversity of Missouri–St. Louis, St Louis, United StatesJ. BaslerDepartment of Physics and Astronomy, University of Missouri-St. Louis, 8001 Natural Bridge Road, St. Louis, MO 63121, USAJosé GuerraUniversity of Missouri–St. Louis, St Louis, United StatesB. B. KahharovConnecticut College, New London, United StatesL. F. BrownDepartment of Physics, Astronomy and Geophysics, Connecticut College, New London, CT 06320, USAT. J. BalonekFoggy Bottom Observatory, Colgate University, 13 Oak Drive, Hamilton, NY 13346, USAB. KapanadzeColgate University, Hamilton, United StatesE. BenítezInstituto de Astronomía, UNAM, Apdo. Postal 70-264, 04510 México DF, MexicoHannu KarttunenUniversidad Nacional Autónoma de México, Mexico City, MexicoA. RamírezInstituto de Astronomía, UNAM, Apdo. Postal 70-264, 04510 México DF, MexicoTakeo KatoUniversidad Nacional Autónoma de México, Mexico City, MexicoG. N. KimeridzeUniversity of Colorado Denver, Denver, United StatesA. C. SadunDepartment of Physics, University of Colorado at Denver, PO Box 173364, Denver, CO 80217-3364, USAP. BoltwoodN. A. KudryavtsevaAstronomical Institute, St.-Petersburg State University, Universitetsky Pr. 28, Petrodvoretz, 198504 St.-Petersburg, RussiaM. LainelaWestern Kentucky University, Bowling Green, United StatesM. T. CariniDepartment of Physics and Astronomy, Western Kentucky University, 1 Big Red Way, Bowling Green, KY 42104, USAL. LanteriWestern Kentucky University, Bowling Green, United StatesD. BarnabyDepartment of Physics and Astronomy, Western Kentucky University, 1 Big Red Way, Bowling Green, KY 42104, USAJ. M. ColomaAgrupació Astronòmica de Sabadell, PO Box 50, 08200 Sabadell, SpainЕ. Г. ЛарионоваAstronomical Institute, St.-Petersburg State University, Universitetsky Pr. 28, Petrodvoretz, 198504 St.-Petersburg, RussiaM. MaesanoStazione Astronomica Vallinfreda, ItalyJ. AgramuntAgrupació Astronòmica de Sabadell, PO Box 50, 08200 Sabadell, SpainN. MarchiliChinese Academy of Sciences, Beijing, ChinaB. Z. DaiUnited Laboratory of Optical Astronomy, Chinese Academy of Sciences, Beijing, PR ChinaGaogang XieUnited Laboratory of Optical Astronomy, Chinese Academy of Sciences, Beijing, PR ChinaG. MassoneChinese Academy of Sciences, Beijing, ChinaJ. R. MattoxDepartment of Natural Sciences, Fayetteville State University, 1200 Murchison Road, Fayetteville, NC 28301, USATalaWanda R. MonroeFayetteville State University, Fayetteville, United StatesF. MontagniD. RodriguezGuadarrama Observatory, C/ San Pablo 5, Villalba 28409, Madrid, SpainI. M. AsfandiyarovUlugh Beg Astronomical Institute, Academy of Sciences of Uzbekistan, 33 Astronomical Str., Tashkent 700052, UzbekistanR. NesciAcademy of Sciences Republic of Uzbekistan, Tashkent, UzbekistanK. NilssonWestern Kentucky University, Bowling Green, United StatesA. AtkersonDepartment of Physics and Astronomy, Western Kentucky University, 1 Big Red Way, Bowling Green, KY 42104, USAJ. C. NobleConnecticut College, New London, United StatesG. NucciarelliHampden–Sydney College, Hampden Sydney, United StatesL. OstoreroAbastumani Astrophysical Observatory, Tbilisi, GeorgiaJ. PapamastorakisUniversity of Perugia, Perugia, ItalyM. PasanenNational Institute for Astrophysics, Rome, ItalyC. S. PetersUniversidad Nacional Autónoma de México, Mexico City, MexicoT. PursimoSt Petersburg University, Saint Petersburg, RussiaP. ReigNational Institute for Astrophysics, Rome, ItalyW. T. RyleNational Institute for Astrophysics, Rome, ItalyS. SclaviAcademy of Sciences Republic of Uzbekistan, Tashkent, UzbekistanL. A. SiguaAbastumani Astrophysical Observatory, Tbilisi, GeorgiaMakoto UemuraDepartment of Astronomy, Faculty of Science, Kyoto University, Kyoto, JapanW. WillsKyoto University, Kyoto, Japan
Repository of Digital Objects for Teaching Research and Culture (University of Valencia)repository2004en
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Аннотация
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 curves obtained by theWEBT 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 fewday 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 bluerwhen- brighter slope in the B − R versus R plane; 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.
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