Статья

The correlated optical and radio variability of BL Lacertae

M. VillataINAF, Osservatorio Astronomico di Torino, Italy e-mail: [email protected]C. M. RaiteriINAF, Osservatorio Astronomico di Torino, Italy e-mail: [email protected]V. M. LarionovAstronomical Institute, St.-Petersburg State University, RussiaM. G. NikolashviliAbastumani Astrophysical Observatory, GeorgiaM. F. AllerDepartment of Astronomy, University of Michigan, MI, USAU. BachMax-Planck-Institut für Radioastronomie, GermanyD. CarosatiArmenzano Astronomical Observatory, ItalyFilip HrochInstitute of Theoretical Physics and Astrophysics, Masaryk University, Czech RepublicM. IbrahimovUlugh Beg Astronomical Institute, Academy of Sciences of Uzbekistan, UzbekistanS. G. JorstadAstronomical Institute, St.-Petersburg State University, RussiaY. Y. KovalevAstro Space Center of Lebedev Physical Institute, RussiaA. LähteenmäkiMetsähovi Radio Observatory, Helsinki University of Technology TKK, FinlandK. NilssonTuorla Observatory, Department of Physics and Astronomy, University of Turku, FinlandH. TeräsrantaMetsähovi Radio Observatory, Helsinki University of Technology TKK, FinlandG. TostiDipartimento di Fisica, Università di Perugia, ItalyA. A. ArkharovPulkovo Observatory, RussiaA. BerdyuginTuorla Observatory, Department of Physics and Astronomy, University of Turku, FinlandP. BoltwoodC. S. BuemiINAF, Osservatorio Astrofisico di Catania, ItalyR. CasasInstitut de Ciències de l'Espai (IEEC-CSIC), Barcelona, SpainP. CharlotCNRS, Laboratoire d'Astrophysique de Bordeaux – UMR5804, FranceJ. M. ColomaA. Di PaolaINAF, Osservatorio Astronomico di Roma, ItalyGianluca Di RicoINAF, Osservatorio Astronomico di Collurania Teramo, ItalyG. N. KimeridzeAbastumani Astrophysical Observatory, GeorgiaT. S. KonstantinovaAstronomical Institute, St.-Petersburg State University, RussiaE. N. KopatskayaAstronomical Institute, St.-Petersburg State University, RussiaYu. A. KovalevAstro Space Center of Lebedev Physical Institute, RussiaO. M. KurtanidzeAbastumani Astrophysical Observatory, GeorgiaL. LanteriINAF, Osservatorio Astronomico di Torino, Italy e-mail: [email protected]Е. Г. ЛарионоваAstronomical Institute, St.-Petersburg State University, RussiaL. V. LarionovaAstronomical Institute, St.-Petersburg State University, RussiaJ.-F. Le CampionCNRS, Laboratoire d'Astrophysique de Bordeaux – UMR5804, FranceP. LetoINAF, Istituto di Radioastronomia, Sezione di Noto, ItalyE. LindforsTuorla Observatory, Department of Physics and Astronomy, University of Turku, FinlandAlan P. MarscherInstitute for Astrophysical Research, Boston University, MA, USAKevin MarshallDepartment of Physics and Astronomy, Georgia State University, GA, USAJohn McFarlandDepartment of Physics and Astronomy, Georgia State University, GA, USAI. M. McHardyDepartment of Physics and Astronomy, University of Southampton, UKH. R. MillerDepartment of Physics and Astronomy, Georgia State University, GA, USAG. NucciarelliDipartimento di Fisica, Università di Perugia, ItalyM. P. OstermanDepartment of Physics and Astronomy, Georgia State University, GA, USAM. PasanenTuorla Observatory, Department of Physics and Astronomy, University of Turku, FinlandT. PursimoNordic Optical Telescope, Roque de los Muchachos Astronomical Observatory, TF, SpainJ. AgramuntA. C. SadunDepartment of Physics, University of Colorado Denver, CO, USAL. A. SiguaAbastumani Astrophysical Observatory, GeorgiaL. SixtovaInstitute of Theoretical Physics and Astrophysics, Masaryk University, Czech RepublicL. O. TakaloTuorla Observatory, Department of Physics and Astronomy, University of Turku, FinlandM. TornikoskiMetsähovi Radio Observatory, Helsinki University of Technology TKK, FinlandC. TrigilioINAF, Osservatorio Astrofisico di Catania, ItalyG. UmanaINAF, Osservatorio Astrofisico di Catania, ItalyGaogang XieNational Astronomical Observatories/Yunnan Observatory, Chinese Academy of Sciences, ChinaX. ZhangPhysics Department, Yunnan University, ChinaShaobing ZhouPhysics Department, Yunnan University, China

Astronomy and Astrophysicsjournal2009en

ABI

Аннотация

Context. Since 1997, BL Lacertae has undergone a phase of high optical activity, with the occurrence of several prominent outbursts. Starting from 1999, the Whole Earth Blazar Telescope (WEBT) consortium has organized various multifrequency campaigns on this blazar, collecting tens of thousands of data points. One of the main issues in the study of this huge dataset has been the search for correlations between the optical and radio flux variations, and for possible periodicities in the light curves. The analysis of the data assembled during the first four campaigns (comprising also archival data to cover the period 1968–2003) revealed a fair optical-radio correlation in 1994–2003, with a delay of the hard radio events of ~100 days. Moreover, various statistical methods suggested the existence of a radio periodicity of ~8 years.Aims. In 2004 the WEBT started a new campaign to extend the dataset to the most recent observing seasons, in order to possibly confirm and better understand the previous results.Methods. In this campaign we have collected and assembled about 11 000 new optical observations from twenty telescopes, plus near-IR and radio data at various frequencies. Here, we perform a correlation analysis on the long-term R-band and radio light curves.Results. In general, we confirm the ~100-day delay of the hard radio events with respect to the optical ones, even if longer (~200–300 days) time lags are also found in particular periods. The radio quasi-periodicity is confirmed too, but the “period” seems to progressively lengthen from 7.4 to 9.3 years in the last three cycles. The optical and radio behaviour in the last forty years suggests a scenario where geometric effects play a major role. In particular, the alternation of enhanced and suppressed optical activity (accompanied by hard and soft radio events, respectively) can be explained in terms of an emitting plasma flowing along a rotating helical path in a curved jet.

Темы

Astrophysics and Cosmic Phenomena Radio Astronomy Observations and Technology Dark Matter and Cosmic Phenomena

Идентификаторы

DOI: 10.1051/0004-6361/200912065

Цитирования и источники

Цитирований: 9 Использованных источников: 30

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