BL Lacertae: complex spectral variability and rapid synchrotron flare detected with BeppoSAX

Abstract

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 (alpha_1 ~ 1.6; alpha_2 ~ 0.15); in December it was well fitted by a single power law (alpha ~ 0.6). During the first BeppoSAX observation BL Lac showed an astonishing variability episode: the 0.3 - 2 keV flux doubled in ~ 20 minutes, while the flux above 4 keV was almost constant. This frequency-dependent event is one of the shortest ever recordered for BL Lac objects and places lower limits on the dimension and the 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 ~ 20% 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, highlightning 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 gamma-ray Spectral Energy Distributions.

19 pages, 6 figures, accepted by Astronomy & Astrophysics

References in corpus (2)

• Internal shocks in the jets of radio-loud quasars
• Multiband optical polarimetry of BL Lac objects with the Nordic Optical Telescope

Cited by in corpus (48)

• The Jet-Disk Connection and Blazar Unification
• The WEBT BL Lac Campaign 2000
• X-Ray Spectral Variability Signatures of Flares in BL Lac Objects
• Spine-sheath layer radiative interplay in subparsec-scale jets and the TeV emission from M87
• The WEBT BL Lacertae Campaign 2001 and its extension
• Discovery of very high energy gamma-ray emission from the low-frequency peaked BL Lacertae object BL Lacertae
• Variable Star Network: World Center for Transient Object Astronomy and Variable Stars
• The correlated optical and radio variability of BL Lacertae. WEBT data analysis 1994-2005
• Coordinated Multiwavelength Observations of BL Lacertae in 2000
• Multi-band optical variability studies of BL Lacertae
• Observing Mkn 421 with XMM--Newton: the EPIC--PN point of view
• The BL Lac objects OQ 530 and S5 0716+714. Simultaneous observations in the X-rays, radio, optical and TeV bands
• Time dependent simulations of multiwavelength variability of the blazar Mrk 421 with a Monte Carlo multi-zone code
• Multi-band optical micro-variability observations of BL Lacertae
• Simultaneous X-ray and optical observations of S5 0716+714 after the outburst of March 2004
• Structure and flux variability in the VLBI jet of BL Lacertae during the WEBT campaigns (1995--2004)
• The first Fermi multifrequency campaign on BL Lacertae: characterizing the low-activity state of the eponymous blazar
• The long-term optical spectral variability of BL Lacertae
• Hard X-ray properties of NuSTAR blazars
• Linking radio and gamma ray emission in Ap Librae
• BeppoSAX Observations of Synchrotron X-ray Emission from Radio Quasars
• A Fast Very High Energy $\gamma$-ray Flare from BL Lacertae during a Period of Multiwavelength activity in June 2015
• BeppoSAX and multiwavelength observations of BL Lacertae in 2000
• Disentangling the synchrotron and Inverse Compton variability in the X-ray emission of the intermediate BL Lac object S5 0716+71
• Modeling the Multiwavelength Spectra and Variability of BL Lacertae in 2000
• A thirteen-year-long broadband view of BL Lac
• Internal shocks and the blazar sequence. Low and intermediate power BL Lac objects
• X-ray spectral studies of TeV gamma-ray emitting blazars
• The TeV emission of Ap Librae: a hadronic interpretation and prospects for CTA
• Swift observations of IBL and LBL objects
• Peak of spectral energy distribution play an important role in intra-day variability of Blazars?
• Wide band X-ray and optical observations of the BL Lac object 1ES 1959+650 in high state
• Seven-Year Multi-Color Optical Monitoring of BL Lacertae Object S5 0716+714
• Optical multi-band observations of BL Lacertae during the outburst of 2005
• Powerful high energy emission of the remarkable BL Lac object S5 0716+714
• BeppoSAX Observations of 1-Jy BL Lacertae Objects - II
• Signature of Inverse Compton emission from blazars
• Evolution of the synchrotron and inverse Compton emissions of the low energy peaked BL Lac object S5 0716+714
• Modeling the Spectral Energy Distribution and Variability of 3C 66A during the WEBT campaign of 2003 -- 2004
• Thermal and non-thermal nature of the soft excess emission from Sersic 159-03 observed with XMM-Newton
• Swift detection of all previously undetected blazars in a micro-wave flux-limited sample of WMAP foreground sources
• Chandra Observations of the X-ray Environment of BL Lacs
• Broadband study of BL Lac during flare of 2020: Spectral evolution and emergence of HBL component
• From Radio to TeV: The surprising Spectral Energy Distribution of AP Librae
• NICER, NuSTAR, and Swift follow-up observations of the $\gamma$-ray flaring blazar BL Lacertae in 2020 August-October
• Extreme blazars
• Using the Markov Chain Monte Carlo method to study the physical properties GeV-TeV BL Lac objects
• The high energy view of blazars