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

• Published in: The Astrophysical journal Vol. 922; no. 2; pp. 140 - 158
• Main Authors: Ravi, Aravind P., Park, Sangwook, Zhekov, Svetozar A., Miceli, Marco, Orlando, Salvatore, Frank, Kari A., Burrows, David N.
• Format: Journal Article
• Language: English
• Published: Philadelphia The American Astronomical Society 01.12.2021; IOP Publishing
• Subjects: Astrophysics; Broadband; Circumstellar matter; Ejecta; Electron temperatures; Emission measurements; Evolution; High resolution; Interstellar medium; Space telescopes; Spectral analysis; Spectral emittance; Spectroscopic analysis; Spectrum analysis; Supernova remnants; Supernovae; X ray spectra; X ray telescopes; X-ray emissions; X-rays
• ISSN: 0004-637X; 1538-4357
• DOI: 10.3847/1538-4357/ac249a

Abstract Based 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.