Study of the gamma-ray source 1AGL J2022+4032 in the Cygnus Region

Abstract

Identification of gamma-ray-emitting Galactic sources is a long-standing problem in astrophysics. One such source, 1AGL J2022+4032, coincident with the interior of the radio shell of the supernova remnant Gamma Cygni (SNR G78.2+2.1) in the Cygnus Region, has recently been identified by Fermi as a gamma-ray pulsar, LAT PSR J2021+4026. We present long-term observations of 1AGL J2022+4032 with the AGILE gamma-ray telescope, measuring its flux and light curve. We compare the light curve of 1AGL J2022+4032 with that of 1AGL J2021+3652 (PSR J2021+3651), showing that the flux variability of 1AGL J2022+4032 appears to be greater than the level predicted from statistical and systematic effects and producing detailed simulations to estimate the probability of the apparent observed variability. We evaluate the possibility that the gamma-ray emission may be due to the superposition of two or more point sources, some of which may be variable, considering a number of possible counterparts. We consider the possibility of a nearby X-ray quiet microquasar contributing to the flux of 1AGL J2022+4032 to be more likely than the hypotheses of a background blazar or intrinsic gamma-ray variabilty of LAT PSR J2021+4026.

arXiv comment7 pages, 7 figures, accepted for publication in Astronomy & Astrophysics

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Cited by in corpus (11)

• Search for Spatially Extended Fermi-LAT Sources Using Two Years of Data
• PSR J2021+4026 in the Gamma Cygni region: the first variable gamma-ray pulsar seen by the Fermi LAT
• Gamma-ray Pulsar Revolution
• The AGILE monitoring of Cygnus X-3: transient gamma-ray emission and spectral constraints
• Gamma-ray observations of Cygnus X-1 above 100 MeV in the hard and soft states
• AGILE detection of Cygnus X-3 γ-ray active states during the period mid-2009/mid-2010
• The Second AGILE Catalog of Gamma-Ray Sources
• An updated list of AGILE bright gamma-ray sources and their variability in pointing mode
• Very Hight Energy Observationa of Shell-Type Supernova Remnants with SHALON Mirror Cherenkov Telescopes
• AGILE study of the gamma-ray emission from the SNR G78.2+2.1 (Gamma Cygni)
• A variability study of the AGILE first catalog of γ-ray sources on 2.3 years of AGILE pointed observations