Based on the first 13.4 yr of Fermi science data in the energy range from 300 MeV to 500 GeV, we discovered a bright GeV gamma-ray source with a ∼5.64 σ detection, named Fermi J1242.5+3236, which has an offset of about 0fdg0996 from a nearby star-forming galaxy NGC 4631. When using the 12-yr data, the detection significance of Fermi J1242.5+3236 is about 4.72 σ. Fermi J1242.5+3236 is a steady point source without significant temporal variability and has a hard gamma-ray photon index of about -1.60 ±0.24. The spatial offset and the hard gamma-ray spectrum disfavor this source as the diffuse gamma-ray emission from this galaxy. This new source might have a possible origin of an unidentified background blazar, which is more likely a high-synchrotron-peaked blazar for its hard gamma-ray photon index. A follow-up optical observation would help distinguish origin of Fermi J1242.5+3236.
@article{arxiv.2212.06305,
title = {Possible Origin of a Newly Discovered GeV Gamma-ray Source Fermi J1242.5+3236},
author = {Xiu-Rong Mo and Ming-Hong Luo and Hong-bin Tan and Qing-Wen Tang and Ruo-Yu Liu},
journal= {arXiv preprint arXiv:2212.06305},
year = {2023}
}
Comments
8 pages,6 figures, published in Research in Astronomy and Astrophysics