2025/07/06 by Oka, Tomohiko, Ishizaki, Wataru, Mori, Masaki +3 · 1 citation
#FOS: Physical sciences #High Energy Astrophysical Phenomena (astro-ph.HE)
paper · doi:10.48550/arxiv.2507.04407
While decades of observations in the TeV gamma-ray band have revealed more than 200~sources with radio or X-ray counterparts, there remain dozens of unidentified TeV sources, which may provide crucial information of cosmic ray (CR) accelerators. HESS J1626-490 is an unidentified TeV gamma-ray source but is expected to originate from CRs that escaped from the nearby supernova remnant (SNR) G335.2+0.1 and are interacting with dense interstellar clouds. To test this scenario, we scrutinize the properties of the SNR and search for non-thermal counterparts by analyzing observational data in the radio, X-ray, and GeV gamma-ray bands. From analysis of the H \sc i and 12CO (J=1-0) line data, we identify the cloud associated with the SNR and compare the morphologies of the cloud and the gamma-ray emission. The distance and age of the SNR are estimated to be 3.3 ± 0.6~kpc and ∼5~kyr, respectively. From X-ray and GeV gamma-ray data analyses, we find an extended GeV gamma-ray emission overlapping with the SNR and H.E.S.S. source regions but no X-ray emission. The location of the peak of the extended GeV emission changes from near the SNR at \lesssim 1~GeV to the H.E.S.S. source at >10~GeV. We find a spectral hardening at ∼50~GeV, which is consistent with the existence of two components in the gamma-ray emission. We find that a combination of emission from the escaped CRs and the SNR itself can reproduce the observed broadband spectrum, on the assumption that the SNR has accelerated protons to \gtrsim100~TeV in the past.