New HST Observations of High Velocity Lyman Alpha and Balmer Alpha in SNR 1987A

TL;DR

This paper presents high velocity Lyman alpha and Balmer alpha observations of SNR 1987A, revealing asymmetries and diffuse emissions linked to the reverse shock and circumstellar environment, enhancing understanding of supernova remnant dynamics.

Contribution

It provides the first detailed modeling of high velocity hydrogen emission lines in SNR 1987A, highlighting asymmetries and diffuse emissions associated with the reverse shock.

Findings

High velocity (~15,000 km/s) hydrogen emission observed.

Asymmetry in emission correlates with radio data.

Diffuse emission possibly excited by nonthermal particles.

Abstract

We describe and model high velocity (~15,000 km/s) Lyman alpha and Balmer alpha emission from supernova remnant 1987A seen in September and October 1997 with the Space Telescope Imaging Spectrograph. Part of this emission comes from a reverse shock located at ~75% of the radius of the inner boundary of the inner circumstellar ring and confined within 30 degrees of the equatorial plane. Departure from axisymmetry in the Lyman alpha and Balmer alpha emission correlates with that seen in nonthermal radio emission and reveals an asymmetry in the circumstellar gas distribution. We also see diffuse high velocity Lyman alpha emission from supernova debris inside the reverse shock that may be due to excitation by nonthermal particles accelerated by the shock.