EGRET observations of active galactic nuclei
- Conference date: 20−22 Sep 1993
- Location: College Park, Maryland (USA)
The full‐sky survey completed by EGRET during Phase 1 of the CGRO Mission resulted in 21 strong detections of active galactic nuclei (AGNs); 17 additional AGNs were marginally detected. All of these objects are radio bright (≳≊1 Jy near 5 GHz), and have flat radio spectra between 2 and 5 GHz. Many have been previously classified as having some combination of ‘‘superluminal’’ VLBI activity, large and rapid time variations, high polarization, etc. Seven strong and 30 marginal sources were detected for which no convincing identification has been found. Several AGNs were detected during the early portions of Phase 2 which had not been detectable during Phase 1.
A number of the sources were sufficiently bright to provide quite accurate energy spectra; all are found to be compatible with power laws over most of the EGRET energy range, although several are also compatible with a knee or roll‐off in the 2–10 GeV range. When compared with fluxes measured in lower frequency bands, the detected energy budget appears in most cases to be dominated by the gamma ray energy flux; a notable exception is Markarian 421 (the closest of the identified EGRET AGN detections), whose multiwavelength spectrum shows comparable νFν in the optical, X‐ray, and gamma ray ranges.
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