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arXiv · 2212.01851

Multiwavelength studies of G298.6$-$0.0: An old GeV supernova remnant interacting with molecular clouds

Paul K. H. Yeung·Aya Bamba·Hidetoshi Sano
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Abstract

Hadronic $γ$-ray sources associated with supernova remnants (SNRs) can serve as stopwatches for the escape of cosmic rays from SNRs, which gradually develops from highest-energy particles to lowest-energy particles with time. In this work, we analyze the 13.7~yr \emph{Fermi}-LAT data to investigate the $γ$-ray feature in/around the SNR G298.6$-$0.0 region. With $γ$-ray spatial analyses, we detect three point-like components. Among them, Src-NE is at the eastern SNR shell, and Src-NW is adjacent to the western edge of this SNR. Src-NE and Src-NW demonstrate spectral breaks at energies around/below 1.8~GeV, suggesting an old SNR age of $>$10~kyr. We also look into the X-ray emission from the G298.6$-$0.0 region, with the Chandra-ACIS data. We detected an extended keV source having a centrally filled structure inside the radio shell. The X-ray spectra are well fit by a model which assumes a collisional ionisation equilibrium of the thermal plasma, further supporting an old SNR age. Based on our analyses of the NANTEN CO- and ATCA-Parkes HI-line data, we determined a kinematic distance of $\sim$10.1~kpc from us to G298.6$-$0.0. This distance entails a large physical radius of the SNR of $\sim$15.5~pc, which is an additional evidence for an old age of $>$10~kyr. Besides, the CO data cube enables us to three-dimensionally locate the molecular clouds (MCs) which are potentially interacting with SNR G298.6$-$0.0 and could account for the hadronic $γ$-rays detected at Src-NE or Src-NW. Furthermore, the multiwavelength observational properties unanimously imply that the SNR--MC interaction occurs mainly in the northeast direction.

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Paul K. H. Yeung, Aya Bamba, Hidetoshi Sano. 2023-01-17. Multiwavelength studies of G298.6$-$0.0: An old GeV supernova remnant interacting with molecular clouds. https://doi.org/10.1093/pasj%2Fpsad006

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