Fermi LARGE AREA TELESCOPE OBSERVATIONS OF BLAZAR 3C 279 OCCULTATIONS BY THE SUN

Abstract

Observations of occultations of bright γ-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 ≈3σ, 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 γ-ray emission at a 3σ confidence level.

Keywords: Sun: X-rays, gamma rays; astroparticle physics; gamma rays: general; occultations; quasars: individual (3C 279).

Figure 1.

Solar track (the solid line is added for guidance) is clearly seen in the residual map (>1 GeV) and corresponds to observations between 2008 September 17 and October 28. The color bar shows counts per pixel, pixel size is $0_{.}^{°}25\times 0_{.}^{°}25$. The central position of the map corresponds to the position of 3C 279 (oversubtracted). Positions of bright sources are shown with circles.