2023/09/04 by Domček, V., Santisteban, J. V. Hernández, Chiotellis, A. +6 · 1 citation
#Astrophysics of Galaxies (astro-ph.GA) #FOS: Physical sciences #Solar and Stellar Astrophysics (astro-ph.SR)
paper · doi:10.48550/arxiv.2309.01768
We present the first optical study of the supernova remnant (SNR) G7.7-3.7, with the aim of determining its evolutionary phase since it has been suggested to be the remnant of SN 386 AD. We obtained narrow-band images in the filters Hα + [NII], Hβ, [OIII], [SII] that revealed faint optical emission in the southern region of the SNR consisting of two filaments elongated in the east-west direction aligned with the X-ray emitting region of the remnant. The filaments were seen in Hα + [NII], [OIII] images and marginally in the [SII] images, with a non-detection in Hβ. Long-slit spectroscopy of three regions along one filament revealed large ratios of [SII] / Hα = (1.6-2.5), consistent with that expected for a shock-heated SNR. The [SII] doublet ratio observed in two of the regions implies an upper limit for the electron density of the gas, with estimates falling below 400 cm-3 and 600 cm-3 in the respective areas. We discuss potential physical mechanisms that formed the observed optical filaments and we suggest that most likely they resulted by a collision of the SNR with a dense circumstellar shell lying at the southern region of the remnant.