Revisiting the Distance, Environment, and Supernova Properties of SNR G57.2+0.8 that Hosts SGR 1935+2154

• Published in: The Astrophysical journal Vol. 905; no. 2; pp. 99 - 110
• Main Authors: Zhou, Ping, Zhou, Xin, Chen, Yang, Wang, Jie-Shuang, Vink, Jacco, Wang, Yuan
• Format: Journal Article
• Language: English
• Published: Philadelphia The American Astronomical Society 01.12.2020; IOP Publishing
• Subjects: Astrophysics; Carbon monoxide; Emission; Explosions; Flux density; Magnetars; Milky Way; Molecular clouds; Molecular gases; Physical properties; Radio bursts; Radio transient sources; Soft gamma-ray repeaters; Supernova; Supernova remnants; Supernovae; Velocity; X-ray bursts; X-ray emissions
• ISSN: 0004-637X; 1538-4357
• DOI: 10.3847/1538-4357/abc34a

We have performed a multiwavelength study of supernova remnant (SNR) G57.2+0.8 and its environment. The SNR hosts the magnetar SGR 1935+2154, which emitted an extremely bright millisecond-duration radio burst on 2020 April 28. We used the 12CO and 13CO J = 1-0 data from the Milky Way Image Scroll Painting CO line survey to search for molecular gas associated with G57.2+0.8, in order to constrain the physical parameters (e.g., the distance) of the SNR and its magnetar. We report that SNR G57.2+0.8 is likely impacting the molecular clouds (MCs) at the local standard of rest (LSR) velocity and excites a weak 1720 MHz OH maser with a peak flux density of 47 mJy beam−1. The chance coincidence of a random OH spot falling in the SNR is ≤12%, and the OH-CO correspondence chance is 7% at the maser spot. This combines to give <1% false probability of the OH maser, suggesting a real maser detection. The LSR velocity of the MCs places the SNR and magnetar at a kinematic distance of 6.6 0.7 kpc. The nondetection of thermal X-ray emission from the SNR and the relatively dense environment suggests G57.2+0.8 be an evolved SNR with an age . The explosion energy of G57.2+0.8 is lower than , which is not very energetic even assuming a high ambient density . This reinforces the opinion that magnetars do not necessarily result from very energetic supernova explosions.