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

Abstract

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.

Monitoring the magnetar SGR 1935+2154 with the MAGIC telescopes

“…This is the most energetic emission ever recorded from these events, with two photons detected above 1 GeV. SGR 1935+2154 is a Galactic magnetar, located at a distance of 6.6-12.5 kpc [6,7]. It is embedded in the supernova remnant SNR G57.2+0.8 and it is likely associated with a molecular cloud (MC; ).…”

The Fast Radio Burst-emitting magnetar SGR 1935+2154 -- proper motion and variability from long-term Hubble Space Telescope monitoring

“…SGR 1935+2154 is one of the most active magnetars in the Galaxy and the possibilities it now offers to observe an FRB-emitting system in intricate detail has compounded its astrophysical interest. It is spatially coincident with the supernova remnant SNR G57.2+08 (Gaensler 2014), which is typically inferred to be the result of the magnetar-producing supernova (Kothes et al 2018;Zhou et al 2020;dos Anjos et al 2021). The supernova itself, based on a study of the remnant, does not appear to be extraordinary by core-collapse standards (Zhou et al 2020), hinting that magnetar production in the deaths of massive stars may be more widespread than initially thought.…”

“…It is spatially coincident with the supernova remnant SNR G57.2+08 (Gaensler 2014), which is typically inferred to be the result of the magnetar-producing supernova (Kothes et al 2018;Zhou et al 2020;dos Anjos et al 2021). The supernova itself, based on a study of the remnant, does not appear to be extraordinary by core-collapse standards (Zhou et al 2020), hinting that magnetar production in the deaths of massive stars may be more widespread than initially thought. This scenario is appealing given the current tension for 'normal' corecollapse supernovae between the theoretical expectations of purely radioactively-powered explosions (Ertl et al 2020;Woosley et al 2021) and observations (Sollerman et al 2021).…”

“…Estimates range anywhere from ∼6 to 14 kpc (e.g. Park et al 2013;Pavlovic et al 2014;Surnis et al 2016;Kothes et al 2018;Zhou et al 2020). For our purposes we will adopt the distance of 6.6 ± 0.7 kpc determined in a recent study by Zhou et al (2020) of molecular clouds impacted by SNR G57.2+08.…”

Observation of burst activity from SGR1935+2154 associated to first galactic FRB with H.E.S.S.

“…Following its discovery in 2014 [9], SGR 1935+2154 has probably become the most burstactive SGR, emitting dozens of X-ray bursts over the past few years [10]. SGR 1935+2154 is associated with the middle-aged galactic SNR G57.2+0.8 at a distance of about 6.6 kpc [11]. In late April and May 2020 SGR 1935+2154 showed renewed X-ray burst activity culminating with a "forest of bursts" as detected by BAT onboard the Neil Gehrels Swift Observatory.…”