Ravi, Aravind P.Aravind P.RaviPark, SangwookSangwookParkZhekov, Svetozar A.Svetozar A.ZhekovMiceli, MarcoMarcoMiceliORLANDO, SalvatoreSalvatoreORLANDOFrank, Kari A.Kari A.FrankBurrows, David N.David N.Burrows2022-05-302022-05-3020210004-637Xhttp://hdl.handle.net/20.500.12386/32109Based on observations with the 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 new deep (∼312 ks) Chandra HETG observation taken in 2018 March as well as archival Chandra grating spectroscopic data taken in 2004, 2007, and 2011 with similarly deep exposures (∼170-350 ks). We perform detailed spectral model fits to quantify changing plasma conditions over the last 14 yr. Recent changes in electron temperatures and volume-emission measures suggest that the shocks moving through the inner ring have started interacting with less dense circumstellar material, probably beyond the inner ring. We find significant changes in the X-ray line-flux ratios (among H- and He-like Si and Mg ions) in 2018, consistent with changes in the thermal conditions of the X-ray-emitting plasma that we infer based on the broadband spectral analysis. Post-shock electron temperatures suggested by line-flux ratios are in the range ∼0.8-2.5 keV as of 2018. We do not yet observe any evidence of substantial abundance enhancement, suggesting that the X-ray emission component from the reverse-shocked metal-rich ejecta is not yet significant in the observed X-ray spectrum.STAMPAenArticle10.3847/1538-4357/ac249a2-s2.0-85120772226https://iopscience.iop.org/article/10.3847/1538-4357/ac249aFIS/05 - ASTRONOMIA E ASTROFISICA