Gamma-ray halo around 3C 279: looking through the Sun on the 8th of October

Understand

We discuss how the solar occultations of bright sources of energetic gamma rays can be used to extract non-trivial physical and astrophysical information, including the angular size of the image when it is significantly smaller than the experiment's angular resolution.

• We analyze the EGRET data and discuss prospects for other instruments.
• The Fermi Gamma Ray Space Telescope will be able to constrain the size of a possible halo around 3C~279 from observations it makes on the 8th of October each year.