Статья

BL Lacertae: Complex spectral variability and rapid synchrotron flaredetected with <i>BeppoSAX</i>

M. RavasioOsservatorio Astronomico di Brera, Via Bianchi 46, 23807 Merate, ItalyG. TagliaferriOsservatorio Astronomico di Brera, Via Bianchi 46, 23807 Merate, ItalyG. GhiselliniOsservatorio Astronomico di Brera, Via Bianchi 46, 23807 Merate, ItalyP. GiommiR. NesciDipartimento di Fisica, Universitá La Sapienza, P.le Aldo Moro 2, 00185 Roma, ItalyE. MassaroDipartimento di Fisica, Universitá La Sapienza, P.le Aldo Moro 2, 00185 Roma, ItalyL. ChiappettiIstituto di Fisica Cosmica G.Occhialini, CNR, Via Bassini 15, 20133 Milano, ItalyA. CelottiSISSA/ISAS, via Beirut 2-4, 34014 Trieste, ItalyL. CostamanteOsservatorio Astronomico di Brera, Via Bianchi 46, 23807 Merate, ItalyL. MaraschiOsservatorio Astronomico di Brera, Via Brera, 28, 20121 Milano, ItalyF. TavecchioOsservatorio Astronomico di Brera, Via Brera, 28, 20121 Milano, ItalyG. TostiOsservatorio Astronomico, Università di Perugia, Via A. Pascoli, 06100 Perugia, ItalyA. TrevesDipartimento di Scienze, Università dell'Insubria, Via Valleggio 11, 22100 Como, ItalyA. WolterOsservatorio Astronomico di Brera, Via Brera, 28, 20121 Milano, ItalyT. BalonekFoggy Bottom Observatory, Colgate University, 13 Oak Drive 13346, Hamilton NY, USAM. CariniDept. of Physics and Astronomy, Western Kentucky University, 1 Big Red Way, Bowling Green, KY 42102-3576, USAT. KatoDept. of Astronomy, Kyoto University, Kitashirakawa-Oiwake-cho, Sakio-ku, Kyoto 606-8502, JapanO. KurtanidzeAbastumani Astrophysical Observatory, 383762, Abastumani, Republic of GeorgiaF. MontagniDipartimento di Fisica, Universitá La Sapienza, P.le Aldo Moro 2, 00185 Roma, ItalyM. NikolashviliAbastumani Astrophysical Observatory, 383762, Abastumani, Republic of GeorgiaJ. NobleDept. of Astronomy, Boston University, 725 Commonwealth Avenue, Boston MA 02215, USAG. NucciarelliOsservatorio Astronomico, Università di Perugia, Via A. Pascoli, 06100 Perugia, ItalyC. M. RaiteriOsservatorio Astronomico di Torino, Strada Osservatorio 20, 10025 Pino Torinese, ItalyS. SclaviDipartimento di Fisica, Universitá La Sapienza, P.le Aldo Moro 2, 00185 Roma, ItalyM. UemuraDept. of Astronomy, Kyoto University, Kitashirakawa-Oiwake-cho, Sakio-ku, Kyoto 606-8502, JapanM. VillataOsservatorio Astronomico di Torino, Strada Osservatorio 20, 10025 Pino Torinese, Italy

2002en

ABI

Аннотация

We report on two BeppoSAX observations of BL Lac (2200+420) performed respectively in June and December 1999, as part of a ToO program to monitor blazars in high states of activity. During both runs the source has been detected up to 100 keV, but it showed quite different spectra: in June it was concave with a very hard component above 5–6 keV (; ); in December it was well fitted by a single power law (). During the first BeppoSAX observation BL Lac showed an astonishing variability episode: the 0.3–2 keV flux doubled in ~ min, while the flux above 4 keV was almost constant. This frequency–dependent event is one of the shortest ever recorded for BL Lac objects and places lower limits on the dimension and magnetic field of the emitting region and on the energy of the synchrotron radiating electrons. A similar but less extreme behaviour is detected also in optical light curves, that display non-simultaneous, smaller fluctuations of ∼ in 20 min. We fit the spectral energy distributions with a homogeneous, one-zone model to constrain the emission region in a very simple but effective SSC + external Compton scenario, highlighting the importance of the location of the emitting region with respect to the Broad Line Region and the relative spectral shape dependence. We compare our data with historical radio to γ-ray Spectral Energy Distributions.

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Идентификаторы

DOI: 10.1051/0004-6361:20011828

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Цитирований: 5Использованных источников: 0

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