CO Observations of the Type Ia Supernova Remnant 3C 397 by the Nobeyama 45-m Radio Telescope: Possible Evidence for the Single-Degenerated Explosion
Abstract
We present a new CO observation toward the Type Ia supernova remnant (SNR) 3C 397 using the Nobeyama 45-m radio telescope at an unprecedent angular resolution of 18''. We newly found that the CO cloud at VLSR = 55.7-62.2 km s-1 (60 km s-1 cloud) shows a good spatial correspondence with the radio continuum shell. We also found an expanding gas motion of the 60 km s-1 cloud with an expansion velocity of 3 km s-1, which is thought to be formed by the pre-and/or post-supernova feedback. By considering the positions of Galactic spiral arms and the X-ray/HI absorption studies, we concluded that 3C 397 is physically associated with the 60 km s-1 cloud rather than the previously known CO cloud at VLSR 30 km s-1. Given that the previously measured pre-shock density is 2-5 cm-3, the expanding motion of the 60 km s-1 cloud was likely formed by the pre-supernova feedback known as optically thick wind. The scenario is consistent with that 3C 397 exploded inside a wind-blown bubble as a single degenerate system.
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