Possible Origin of a Newly Discovered GeV Gamma-Ray Source Fermi J1242.5+3236. (1st February 2023)

• Record Type: Journal Article
• Authors: Mo, Xiu-Rong; Luo, Ming-Hong; Tan, Hong-Bin; Tang, Qing-Wen; Liu, Ruo-Yu
• Is Part Of: Research in astronomy and astrophysics. Volume 23:Number 2(2023)
• Publication Date: 2023-02-01
• Subjects: galaxies: starburst -- galaxies: star formation -- gamma-rays: galaxies -- galaxies: active; Astronomy -- Periodicals; Astrophysics -- Periodicals; 520.5
• DOI: 10.1088/1674-4527/acab45
• Languages: English
• ISSNs: 1674-4527

Abstract

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 ∼5.64 σ detection, named Fermi J1242.5+3236, which has an offset of about 0.°0996 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.