The Post-impact Evolution of the X-ray Emitting Gas in SNR 1987A Viewed by XMM-Newton

TL;DR

This study analyzes over a decade of X-ray data from SNR 1987A, revealing the evolution of its hot plasma components, chemical abundances, and shock interactions, providing insights into the remnant's post-impact development.

Contribution

It presents a detailed, multi-epoch X-ray spectral analysis of SNR 1987A, highlighting the evolution of plasma components and chemical abundances with new insights into shock dynamics.

Findings

The low-temperature plasma emission measure is decreasing, indicating the blast wave leaving the equatorial ring.

The high-temperature plasma emission measure is increasing as the blast wave propagates into high-latitude gas.

Fe K lines show increasing flux and energy, suggesting a hot component from shock-heated Fe-rich ejecta or reflected shocks.

Abstract

Since 1996 the blast wave driven by SN 1987A has been interacting with the dense circumstellar material, which provides us with a unique opportunity to study the early evolution of a newborn supernova remnant (SNR). Based on the XMM-Newton RGS and EPIC-pn X-ray observations from 2007 to 2019, we investigated the post-impact evolution of the X-ray emitting gas in SNR 1987A. The hot plasma is represented by two non-equilibrium ionization components with temperature of $\sim0.6$ keV and $\sim2.5$ keV. The low-temperature plasma has a density $\sim2400$ cm$^{-3}$, which is likely dominated by the lower density gas inside the equatorial ring (ER). The high-temperature plasma with a density $\sim550$ cm$^{-3}$ could be dominated by the H II region and the high-latitude material beyond the ring. In the last few years, the emission measure of the low-temperature plasma has been decreasing, indicating that the blast wave has left the main ER. But the blast wave is still propagating into the high-latitude gas, resulting in the steadily increase of the high-temperature emission measure. In the meantime, the average abundances of N, O, Ne, and Mg are found to be declining, which may reflect the different chemical compositions between two plasma components. We also detected the Fe K lines in most of the observations, showing increasing flux and centroid energy. We interpret the Fe K lines as from a third hot component, which may come from the reflected shock-heated gas or originate from Fe-rich ejecta clumps, shocked by the reverse shock.