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| Format: | Preprint |
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2025
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| Online-Zugang: | https://arxiv.org/abs/2501.05725 |
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| _version_ | 1866916561026023424 |
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| author | Shen, Yun-Zhi Chen, Yang Zhang, Xiao Tu, Tian-Yu Zhong, Wen-Juan Zhang, Qian-Qian Liu, Qian-Cheng |
| author_facet | Shen, Yun-Zhi Chen, Yang Zhang, Xiao Tu, Tian-Yu Zhong, Wen-Juan Zhang, Qian-Qian Liu, Qian-Cheng |
| contents | We investigate the molecular environment of the supernova remnant (SNR) Kesteven 67 (G18.8+0.3) using observations in $^{12}$CO, $^{13}$CO, HCO$^+$,and HCN lines and possible associated $γ$-ray emission using 16-yr Fermi-LAT observation. We find that the SNR is closely surrounded by a molecular belt in the southeastern boundary, with the both recessed in the band-like molecular gas structure along the Galactic plane. The asymmetric molecular line profiles are widely present in the surrounding gas around local-standard-of-rest velocity +20 km s$^{-1}$. The secondary components centered at $\sim$+16km s$^{-1}$ in the belt and $\sim$+26 km s$^{-1}$ in the northern clump can be ascribed to the motion of a wind-blown molecular shell. This explanation is supported by the position-velocity diagram along a line cutting across the remnant, which shows an arc-like pattern, suggesting an expanding gas structure. With the simulation of chemical effects of shock propagation, the abundance ratios $N$(HCO$^+$)/$N$($^{12}$CO) $\sim2.6\times 10^{-5}$--$3.6\times 10^{-4}$ obtained in the belt can be more naturally interpreted by the wind-driven bubble shock than by the SNR shock. The belt and northern clump are very likely to be parts of an incomplete molecular shell of bubble driven by O-type progenitor star's wind. The analysis of 0.2--500 GeV $γ$-ray emission uncovers a possible point source (`Source~A') about 6.5$σ$ located in the north of the SNR, which essentially corresponds to northern molecular clump. Our spectral fit of the emission indicates that a hadronic origin is favored by the measured Galactic number ratio between CR electrons and protons $\sim0.01$. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2501_05725 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Expanding Molecular Shell and Possible γ-ray Source Associated with Supernova Remnant Kesteven 67 Shen, Yun-Zhi Chen, Yang Zhang, Xiao Tu, Tian-Yu Zhong, Wen-Juan Zhang, Qian-Qian Liu, Qian-Cheng High Energy Astrophysical Phenomena We investigate the molecular environment of the supernova remnant (SNR) Kesteven 67 (G18.8+0.3) using observations in $^{12}$CO, $^{13}$CO, HCO$^+$,and HCN lines and possible associated $γ$-ray emission using 16-yr Fermi-LAT observation. We find that the SNR is closely surrounded by a molecular belt in the southeastern boundary, with the both recessed in the band-like molecular gas structure along the Galactic plane. The asymmetric molecular line profiles are widely present in the surrounding gas around local-standard-of-rest velocity +20 km s$^{-1}$. The secondary components centered at $\sim$+16km s$^{-1}$ in the belt and $\sim$+26 km s$^{-1}$ in the northern clump can be ascribed to the motion of a wind-blown molecular shell. This explanation is supported by the position-velocity diagram along a line cutting across the remnant, which shows an arc-like pattern, suggesting an expanding gas structure. With the simulation of chemical effects of shock propagation, the abundance ratios $N$(HCO$^+$)/$N$($^{12}$CO) $\sim2.6\times 10^{-5}$--$3.6\times 10^{-4}$ obtained in the belt can be more naturally interpreted by the wind-driven bubble shock than by the SNR shock. The belt and northern clump are very likely to be parts of an incomplete molecular shell of bubble driven by O-type progenitor star's wind. The analysis of 0.2--500 GeV $γ$-ray emission uncovers a possible point source (`Source~A') about 6.5$σ$ located in the north of the SNR, which essentially corresponds to northern molecular clump. Our spectral fit of the emission indicates that a hadronic origin is favored by the measured Galactic number ratio between CR electrons and protons $\sim0.01$. |
| title | Expanding Molecular Shell and Possible γ-ray Source Associated with Supernova Remnant Kesteven 67 |
| topic | High Energy Astrophysical Phenomena |
| url | https://arxiv.org/abs/2501.05725 |