Study of the γ-ray source 1AGL J2022+4032 in the Cygnus region

CHEN, A.; PIANO, G.; TAVANI, M.; TROIS, A.; DUBNER, G.; GIACANI, E. & 55 COAUTHORS

ASTRONOMY AND ASTROPHYSICS

EDP SCIENCES S A

Año: 2011 vol. 525 p. 33 - 40

0004-6361

Context. Identification of γ-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 γ-ray pulsar, LAT PSR J2021+4026. Aims: We present long-term observations of 1AGL J2022+4032 with the AGILE γ-ray telescope, measuring its flux and light curve. Methods: 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. Results: We evaluate the possibility that the γ-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. Conclusions: 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 γ-ray variabilty of LAT PSR J2021+4026.