Modeling the Spectral Energy Distribution and Variability of 3C 66A during the WEBT campaign of 2003 -- 2004

Abstract

The BL Lac object 3C 66A was observed in an extensive multiwavelength monitoring campaign from July 2003 till April 2004. The spectral energy distribution (SED) was measured over the entire electromagnetic spectrum, with flux measurements from radio to X-ray frequencies and upper limits in the very high energy (VHE) gamma-ray regime. Here, we use a time-dependent leptonic jet model to reproduce the SED and optical spectral variability observed during our multiwavelength campaign. Our model simulations could successfully reproduce the observed SED and optical light curves and predict an intrinsic cutoff value for the VHE gamma-ray emission at ~ 4 GeV. The effect of the optical depth due to the intergalactic infrared background radiation (IIBR) on the peak of the high-energy component of 3C 66A was found to be negligible. Also, the presence of a broad line region (BLR) in the case of 3C 66A may play an important role in the emission of gamma-ray photons when the emission region is very close to the central engine, but further out, the production mechanism of hard X-ray and gamma-ray photons becomes rapidly dominated by synchrotron self-Compton emission. We further discuss the possibility of an observable X-ray spectral variability pattern. The simulated results do not predict observable hysteresis patterns in the optical or soft X-ray regimes for major flares on multi-day time scales.

arXiv comment23 pages, 9 figures, submitted to and accepted for publication in ApJ

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• Fourier Analysis of Blazar Variability
• Linking radio and gamma ray emission in Ap Librae
• Balancing the Cosmic Energy Budget: The Cosmic X-ray Background, Blazars and the Compton Thick AGN Fraction
• The WEBT Campaign on the Intermediate BL Lac Object 3C66A in 2007-2008
• Polarization Signatures of Relativistic Magnetohydrodynamic Shocks in the Blazar Emission Region - I. Force-free Helical Magnetic Fields
• Polarization Signatures of Kink Instabilities in the Blazar Emission Region from Relativistic Magnetohydrodynamic Simulations
• Probing the Jets of Blazars Using the Temporal Symmetry of Their Multi-Wavelength Outbursts
• First-Principle-Integrated Study of Blazar Synchrotron Radiation and Polarization Signatures from Magnetic Turbulence
• Spectral Energy Distribution variation in BL Lacs and FSRQs
• Circumnuclear Dust in AP Librae and the source of its VHE emission
• Mechanism of very high energy radiation in BL Lacertae object 3C 66A
• Quantitative comparisons of VHE gamma-ray blazar flares with relativistic reconnection models
• Multi-wavelength emission from 3C 66A: clues on its redshift and gamma-ray emission location