An Echo of Supernova 2008bk

TL;DR

This paper reports the discovery and analysis of a light echo around Supernova 2008bk, revealing dust properties and environmental conditions through HST archival images.

Contribution

It provides the first detailed analysis of a light echo around SN 2008bk, including dust location, composition, and implications for the supernova's extinction and environment.

Findings

Light echo is a partial ring brighter to the north and east.

Dust responsible for the echo is located about 15 pc from the SN.

The supernova experienced minimal overall extinction.

Abstract

I have discovered a prominent light echo around the low-luminosity Type II-Plateau Supernova (SN) 2008bk in NGC 7793, seen in archival images obtained with the Wide Field Channel of the Advanced Camera for Surveys on-board the Hubble Space Telescope (HST). The echo is a partial ring, brighter to the north and east than to the south and west. The analysis of the echo I present suggests that it is due to the SN light pulse scattered by a sheet, or sheets, of dust located ~15 pc from the SN. The composition of the dust is assumed to be of standard Galactic diffuse interstellar grains. The visual extinction of the dust responsible for the echo is A_V ~ 0.05 mag, in addition to the extinction due to the Galactic foreground toward the host galaxy. That the SN experienced much less overall extinction implies that it is seen through a less dense portion of the interstellar medium in its environment. The late-time HST photometry of SN 2008bk also clearly demonstrates that the progenitor star has vanished.