Fermi LARGE AREA TELESCOPE OBSERVATIONS OF BLAZAR 3C 279 OCCULTATIONS BY THE SUN
Barbiellini, G. ; Bastieri, D. ; Bechtol, K. ; Cavazzuti, E. ; Giommi, P. ;
Apr - 2014
DOI: 10.1088/0004-637X/784/2/118
ISSN : 0004-637X ;
journal : The Astrophysical Journal

Volume : 784 ; Issue : 2
type: Article Journal

Abstract
Observations of occultations of bright \gamma-ray sources by the Sun may reveal predicted pair halos around blazars and/or new physics, such as, e.g., hypothetical light dark matter particles—axions. We use Fermi Gamma-Ray Space Telescope (Fermi) data to analyze four occultations of blazar 3C 279 by the Sun on October 8 each year from 2008 to 2011. A combined analysis of the observations of these occultations allows a point-like source at the position of 3C 279 to be detected with significance of 3\sigma, but does not reveal any significant excess over the flux expected from the quiescent Sun. The likelihood ratio test rules out complete transparency of the Sun to the blazar \gamma-ray emission at a 3\sigma confidence level.

keywords : Fermi LAT,High Energy Astrophysics,Sun: X-rays,astroparticle physics,gamma rays,gamma rays: general,occultations,quasars: individual (3C 279)