High Resolution Spectroscopy of SN1987A's Rings: He I 10830 and H-alpha from the Hotspots

TL;DR

This study provides high-resolution spectroscopic analysis of SN1987A's ring hotspots, revealing differences in line profiles of He I 10830 and H-alpha, which indicate varying shock velocities and gas temperatures.

Contribution

First high-dispersion spectra of He I 10830 from SN1987A's hotspots, comparing line profiles to H-alpha and [N II], revealing shock-related gas dynamics.

Findings

He I profiles are broader than H-alpha and [N II]

He I shows enhanced high-speed emission with asymmetry

Different line profiles suggest distinct shock velocities and gas temperatures

Abstract

We present the first high-dispersion spectroscopy of He I 10830 from the hotspots in the ring around SN1987A, obtained at Gemini South, spatially resolving the near and far sides of the ring. We compare these line profiles to similar echelle spectra of H$\alpha$ and [N II] 6583 obtained at the Magellan Observatory. We find that the He I profiles are much broader than H-alpha or [N II], but the He I profiles also have different shapes -- they have enhanced emission at high speeds, with extra blueshifted emission on the north side of the ring, and extra redshifted emission on the south side. To explain this, we invoke a simple geometric picture where the extra He I emission traces hotter gas from faster shocks that strike the apex of the hotspots directly, while the H-alpha preferentially traces cooler lower-ionization gas from slower transverse shocks that penetrate into the sides of the ring.