Spectral Evolution of the X-Ray Remnant of SN 1987A: A High Resolution Chandra HETG Study

Based on continuing observations in the X-ray energy band using Chandra X-ray Observatory, we present the latest spectral evolution of the X-ray remnant of SN 1987A (SNR 1987A). We present a high-resolution spectroscopic analysis using our latest deep (314 ks) Chandra HETG observation in March 2018. We perform detailed spectral model-fits to quantify changing plasma conditions over the last 14 years. Changing electron temperatures and volume emission measures suggest that shocks moving through the inner ring have started interacting with less dense circumstellar material (CSM), probably beyond the inner ring. Heα to Lyα line flux ratios for the Si and Mg ions have considerably decreased (by ~40%) between 2011 and 2018, consistent with changing electron temperatures. We place an upper limit on the recently suggested thermal line broadening. We do not yet observe any clear evidence of substantial abundance enhancement, suggesting that the X-ray emission component from the reverse shocked ejecta is not yet significant.