Is the Universe More Transparent to Gamma Rays Than Previously Thought?

Abstract

The MAGIC collaboration has recently reported the detection of the strong gamma-ray blazar 3C279 during a 1-2 day flare. They have used their spectral observations to draw conclusions regarding upper limits on the opacity of the Universe to high energy gamma-rays and, by implication, upper limits on the extragalactic mid-infrared background radiation. In this paper we examine the effect of gamma-ray absorption by the extragalactic infrared radiation on intrinsic spectra for this blazar and compare our results with the observational data on 3C279. We find agreement with our previous results, contrary to the recent assertion of the MAGIC group that the Universe is more transparent to \gray s than our calculations indicate. Our analysis indicates that in the energy range between ~80 and ~500 GeV, 3C279 has a best-fit intrinsic spectrum with a spectral index ~1.78 using our fast evolution model and ~2.19 using our baseline model. However, we also find that spectral indices in the range of 0.0 to 3.0 are almost as equally acceptable as the best fit spectral indices. Assuming the same intrinsic spectral index for this flare as for the 1991 flare from 3C279 observed by EGRET, viz., 2.02, which lies between our best fit indices, we estimate that the MAGIC flare was ~3 times brighter than the EGRET flare observed 15 years earlier.

version accepted for publication in ApJ Letters

References in corpus (18)

• The Cosmic Infrared Background: Measurements and Implications
• Very-High-Energy Gamma Rays from a Distant Quasar: How Transparent Is the Universe?
• The Bulk of the Cosmic Infrared Background Resolved by ISOCAM
• Intergalactic Photon Spectra from the Far IR to the UV Lyman Limit for $0<z<6$ and the Optical Depth of the Universe to High Energy Gamma-Rays
• Implications of Cosmological Gamma-Ray Absorption II. Modification of gamma-ray spectra
• PAHs contribution to the infrared output energy of the Universe at z~2
• Absorption of 10--200 Gev Gamma Rays by Radiation from BLR in Blazars
• An Empirically Based Calculation of the Extragalactic Infrared Background
• Blazar Gamma-Rays, Shock Acceleration, and the Extragalactic Background Light
• Hard TeV spectra of blazars and the constraints to the IR intergalactic background
• An Empirically Based Model for Predicting Infrared Luminosity Functions, Deep Infrared Galaxy Counts and the Diffuse Infrared Background
• A Bridge from Optical to Infrared Galaxies: Explaining Local Properties, Predicting Galaxy Counts and the Cosmic Background Radiation
• Corrected Table for the Parametric Coefficients for the Optical Depth of the Universe to Gamma-rays at Various Redshifts
• Modification of the gamma-ray spectra by internal absorption in OVV blazars: The example cases of 3C 273 and 3C 279
• Absorption of 10 Gev--1 Tev Gamma Rays by Radiation from Broad-Line Region in 3C 279
• The Spectrum of 1ES0229 + 200 and the Cosmic Infrared Background
• A Simple Analytic Treatment of the Intergalactic Absorption Effect in Blazar Gamma-ray Spectra
• Hard Electron Energy Distribution in the Relativistic Shocks of GRB Afterglows

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