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arXiv · 2212.06305

Possible Origin of a Newly Discovered GeV Gamma-ray Source Fermi J1242.5+3236

Xiu-Rong Mo·Ming-Hong Luo·Hong-bin Tan·Qing-Wen Tang·Ruo-Yu Liu
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Abstract

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 $\sim$5.64 $\sigma$ 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 $\sigma$. 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 $\pm$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.

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Xiu-Rong Mo, Ming-Hong Luo, Hong-bin Tan, Qing-Wen Tang, Ruo-Yu Liu. 2022-12-13. Possible Origin of a Newly Discovered GeV Gamma-ray Source Fermi J1242.5+3236. https://doi.org/10.1088/1674-4527/acab45

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