# Collisionless shock heating of heavy ions in SN 1987A

## TL;DR

This study uses high-resolution X-ray observations and 3-D hydrodynamic simulations of SN 1987A to investigate collisionless shock heating, revealing that ion temperatures exceed proton temperatures and increase linearly with ion mass.

## Contribution

It introduces a novel analysis method combining observations with detailed simulations to measure ion and proton temperatures in supernova remnant shocks.

## Key findings

- Ion to proton temperature ratio is always above one.
- Ion temperature increases linearly with ion mass.
- The method accurately reproduces spectral line broadening.

## Abstract

Astrophysical shocks at all scales, from those in the heliosphere up to the cosmological shock waves, are typically "collisionless", because the thickness of their jump region is much shorter than the collisional mean free path. Across these jumps, electrons, protons, and ions are expected to be heated at different temperatures. Supernova remnants (SNRs) are ideal targets to study collisionless processes because of their bright post-shock emission and fast shocks. Although optical observations of Balmer-dominated shocks in young SNRs showed that the post-shock proton temperature is higher than the electron temperature, the actual dependence of the post-shock temperature on the particle mass is still widely debated. We tackle this longstanding issue through the analysis of deep multi-epoch and high-resolution observations of the youngest nearby supernova remnant, SN 1987A, made with the Chandra X-ray telescope. We introduce a novel data analysis method by studying the observed spectra in close comparison with a dedicated full 3-D hydrodynamic simulation. The simulation is able to reproduce self-consistently the whole broadening of the spectral lines of many ions altogether. We can therefore measure the post shock temperature of protons and selected ions through comparison of the model with observations. We have obtained information about the heating processes in collisional shocks by finding that the ion to proton temperature ratio is always significantly higher than one and increases linearly with the ion mass for a wide range of masses and shock parameters.