Multi-wavelength observations of blazar AO 0235+164 in the 2008-2009 flaring state

Abstract

The blazar AO 0235+164 (z = 0.94) has been one of the most active objects observed by Fermi Large Area Telescope (LAT) since its launch in Summer 2008. In addition to the continuous coverage by Fermi, contemporaneous observations were carried out from the radio to γ -ray bands between 2008 September and 2009 February. In this paper, we summarize the rich multi-wavelength data collected during the campaign (including F-GAMMA, GASP- WEBT, Kanata, OVRO, RXTE, SMARTS, Swift, and other instruments), examine the cross-correlation between the light curves measured in the different energy bands, and interpret the resulting spectral energy distributions in the context of well-known blazar emission models. We find that the γ -ray activity is well correlated with a series of near-IR/optical flares, accompanied by an increase in the optical polarization degree. On the other hand, the X-ray light curve shows a distinct 20 day high state of unusually soft spectrum, which does not match the extrapolation of the optical/UV synchrotron spectrum. We tentatively interpret this feature as the bulk Compton emission by cold electrons contained in the jet, which requires an accretion disk corona with an effective covering factor of 19% at a distance of 100 Rg . We model the broadband spectra with a leptonic model with external radiation dominated by the infrared emission from the dusty torus.

48 pages, 8 figures

References in corpus (17)

• Fermi Large Area Telescope Bright Gamma-ray Source List
• Magnetic acceleration of relativistic AGN jets
• Modeling the Emission Processes in Blazars
• Multifrequency monitoring of the blazar 0716+714 during the GASP-WEBT-AGILE campaign of 2007
• Radio/gamma-ray time delay in the parsec-scale cores of active galactic nuclei
• The Outburst of the Blazar AO 0235+164 in 2006 December: Shock-in-Jet Interpretation
• Testing the inverse-Compton catastrophe scenario in the intra-day variable blazar S5 0716+71, III. Rapid and correlated flux density variability from radio to sub-mm bands
• Multifrequency variability of the blazar AO 0235+164. The WEBT campaign in 2004-2005 and long-term SED analysis
• Bulk Comptonization spectra in blazars
• Radio-to-UV monitoring of AO 0235+164 by the WEBT and Swift during the 2006--2007 outburst
• Harmonic QPOs and Thick Accretion Disk Oscillations in BL Lac Object AO 0235+164
• A structure and energy dissipation efficiency of relativistic reconfinement shocks
• Simultaneous Radio to (Sub-) mm-Monitoring of Variability and Spectral Shape Evolution of potential GLAST Blazars
• High-Energy Aspects of Astrophysical Jets
• Spectroscopic monitoring of the BL Lac object AO 0235+164
• Polarization of synchrotron emission from relativistic reconfinement shocks
• Monitoring the radio spectra of selected blazars in the Fermi-GST era. The Effelsberg 100 m telescope covering the cm band

Cited by in corpus (26)

• Constraining the Location of Gamma-Ray Flares in Luminous Blazars
• Probing Acceleration and Turbulence at Relativistic Shocks in Blazar Jets
• Temporal Correlations Between Optical and Gamma-ray Activity in Blazars
• Comprehensive Monitoring of Gamma-ray Bright Blazars. I. Statistical Study of Optical, X-ray, and Gamma-ray Spectral Slopes
• Quasi-Periodic Oscillations in the long term radio light curves of the blazar AO 0235+164
• The F-GAMMA program: Multi-frequency study of Active Galactic Nuclei in the Fermi era. Program description and the first 2.5 years of monitoring
• Constraining the Physical Conditions in the Jets of Gamma-Ray Flaring Blazars using Centimeter-Band Polarimetry and Radiative Transfer Simulations. I. Data and Models for 0420-014, OJ 287, and 1156+295
• The Variability and Period Analysis for the BL Lac AO 0235+164
• Detection of a quasi-periodic oscillation in the optical light curve of the remarkable blazar AO 0235+164
• Curvature of the spectral energy distribution, the dominant process for inverse Compton component and other jet properties in Fermi 2LAC blazars
• A comprehensive study on the variation phenomena of AO 0235+164
• A Multi-wavelength View of OJ 287 Activity in 2015-2017: Implications of Spectral Changes on Central-engine Models and MeV-GeV Emission Mechanism
• Study of correlation between optical flux and polarization variations in BL Lac objects
• The $\gamma$-ray sky seen at X-ray energies II: the Swift hunt of Fermi BL Lac objects among unidentified gamma-ray sources
• Correlation between optical and $\gamma$-ray flux variations in BL Lacs
• General Physical Properties of Gamma-Ray-emitting Radio Galaxies
• Multi-wavelength temporal variability of the blazar PKS 1510-089
• Multiwavelength variability of the blazar AO 0235+164
• The Repeating Flaring Activity of Blazar AO 0235+164
• Study of variability in long-term multiwavelength optical lightcurves of blazar AO 0235+164
• Monte-Carlo Applications for Partially Polarised Inverse External-Compton Scattering (MAPPIES) -- I. Description of the code and First Results
• The flaring activity of blazar AO 0235+164 during year 2021
• Monte-Carlo Applications for Partially Polarized Inverse External-Compton Scattering (MAPPIES) II -- Application to the UV/Soft X-ray Excess in Blazar Spectra
• Constraints on VHE gamma-ray emission of Flat Spectrum Radio Quasars with the MAGIC telescopes
• A numerical study on the role of instabilities on multi-wavelength emission signatures of blazar jets
• Distinguishing radiation mechanisms and particle populations in blazar jets through long-term multi-band monitoring with RINGO3 and Fermi