BeppoSAX and multiwavelength observations of BL Lacertae in 2000

Abstract

We present two BeppoSAX observations of BL Lac (2200+420) as part of a multiwavelength campaign performed in 2000. The source was in different states of activity: in June, the X-ray spectrum was faint and hard (alpha sim 0.8), with positive residuals towards low energies. In October we detected the highest [2-10] keV flux ever measured for the source. During this observation, the spectrum was soft (alpha sim 1.56) up to 10 keV, while above this energy a hard component was dominating. The BeppoSAX data are confirmed by simultaneous RXTE short observations. During the first observation the soft X-ray flux was variable on timescales of a few hours, while the hard X-ray flux was almost constant. During the second observation, instead, the soft spectrum displayed an erratic behaviour with large variations (up to factors 3-4) on timescales smaller than 2 hrs. The analysis of the multiwavelength SED of October evidenced an intriguing feature: the optical and X-ray sections of the SED are misaligned, while in the prevailing standard picture, they are both thought to be produced via synchrotron emission. We suggested four scenarios to account for this discrepancy: a higher than galactic dust-to-gas ratio towards the source, the first detection of bulk Compton emission in the X-ray band, the presence of two synchrotron emitting regions located at different distances from the nucleus, the detection of a Klein-Nishina effect on the synchrotron spectrum. We evidenced the favorable and critical points of each scenario, but, at present, we cannot discriminate between them.

arXiv comment13 pages, 8 figures, accepted by A&A

References in corpus (25)

• Maps of Dust IR Emission for Use in Estimation of Reddening and CMBR Foregrounds
• A Unifying View of the Spectral Energy Distributions of Blazars
• A theoretical unifying scheme for gamma-ray bright blazars
• AGN Black Hole Masses and Bolometric Luminosities
• The Connection between X-ray- and Radio-Selected BL Lacertae Objects
• The Soft X-Ray Properties of a Complete Sample of Optically Selected Quasars II. Final Results
• Comptonization of Infrared Radiation from Hot Dust by Relativistic Jets in Quasars
• Internal shocks in the jets of radio-loud quasars
• Jets and accretion processes in Active Galactic Nuclei: further clues
• On Pair Content and Variability of Sub-Parsec Jets in Quasars
• The WEBT BL Lac Campaign 2000
• Low power BL Lacertae objects and the blazar sequence: Clues on the particle acceleration process
• Rapid X-ray Variability of the BL Lacertae Object PKS 2155-304
• Observations of a Correlated Gamma-Ray and Optical Flare for BL Lacertae
• X-ray Synchrotron Spectral Hardenings from Compton and Synchrotron Losses in Extended Chandra Jets
• X-ray Emission of Mkn 421: New Clues From Its Spectral Evolution. I. Temporal Analysis
• X-ray Observations of BL Lacertae During 1997 Outburst and its Association with Quasar-like Characteristics
• The BL Lac objects OQ 530 and S5 0716+714. Simultaneous observations in the X-rays, radio, optical and TeV bands
• Supermassive Black Hole Masses of AGNs with Elliptical Hosts
• Analyzing the Multiwavelength Spectrum and Variability of BL Lacertae During the July 1997 Outburst
• BL Lacertae: complex spectral variability and rapid synchrotron flare detected with BeppoSAX
• ASCA and contemporaneous ground-based observations of the BL Lacertae objects 1749+096 and 2200+420 (BL Lac)
• Evidence for the evolutionary sequence of blazars: different types of accretion flows in BL Lac objects
• BeppoSAX and multiwavelength observations of BL Lacertae in 2000
• BeppoSAX Observations of 1 Jy BL Lacertae Objects. I

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• Coordinated Multiwavelength Observations of BL Lacertae in 2000
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• BeppoSAX and multiwavelength observations of BL Lacertae in 2000
• XMM-Newton observations of the TeV BL Lac object PKS 2155--304 in 2006: signature of inverse Compton X-ray emission?
• X-ray emission from the blazar AO 0235+16: the XMM-Newton and Chandra point of view
• 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
• BL Lacertae: X-ray spectral evolution and a black-hole mass estimate
• 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
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• Monte-Carlo Applications for Partially Polarised Inverse External-Compton Scattering (MAPPIES) -- I. Description of the code and First Results
• Monte-Carlo Applications for Partially Polarized Inverse External-Compton Scattering (MAPPIES) II -- Application to the UV/Soft X-ray Excess in Blazar Spectra