Abstract
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 nonequilibrium ionization components with temperatures of ∼0.6 keV and ∼2.5 keV. The low-temperature plasma has a density ∼2400 cm−3, which is likely dominated by the lower-density gas inside the equatorial ring (ER). The high-temperature plasma with a density ∼550 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 steady increase of the high-temperature emission measure. Meanwhile, the average abundances of N, O, Ne, and Mg are found to be declining, which may reflect the different chemical compositions between the two plasma components. We also detected Fe K lines in most of the observations, showing increasing flux and centroid energy. We interpret the Fe K lines as originating 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.
Highlights
As the nearest supernova (SN) observed since Kepler’s SN of 1604, SN 1987A provides us with a unique opportunity to observe in detail the onset of supernova remnant (SNR) formation and subsequent evolution for an SN whose observational properties are known in detail
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)
SN 1987A is surrounded by a peculiar circumstellar material (CSM) system represented by three coaxial rings, the origin of which may be explained by the merging of a binary system at about 20,000 yr before the explosion (Podsiadlowski et al 1992; Morris & Podsiadlowski 2007) or by collisions of a fast wind colliding with material from an earlier slow wind, during the progenitor’s post main sequence evolution (Chita et al 2008)
Summary
As the nearest supernova (SN) observed since Kepler’s SN of 1604, SN 1987A provides us with a unique opportunity to observe in detail the onset of supernova remnant (SNR) formation and subsequent evolution for an SN whose observational properties are known in detail. Starting from ∼ 4000 days, the blast wave encountered the dense clumps protruding from the inner edge of the ER, as evidenced by the appearance of several “hot spots” in the optical band (e.g., Sonneborn et al 1998; Lawrence et al 2000) Corresponding to this —as first observed by Chandra since ∼ 4600 days— the soft X-ray flux of SNR 1987A was found to exceed the linear extrapolation of the ROSAT light curve and brighten more rapidly than observed by ROSAT (Burrows et al 2000; Park et al 2002). The overall X-ray light curve has been well reproduced by three-dimensional hydrodynamic/magnetohydrodynamic simulations (e.g., Orlando et al 2015, 2019, 2020) These simulations indicate that the X-ray emission is dominated first by the shocked H II region, by the shocked dense ring, and that SNR 1987A will enter a third phase around 32–34 years after the explosion, which will be dominated by the SN ejecta heated by the reverse shock. This paper is organized as follows: Section 2 describes the observations and data reduction procedure, Section 3 presents the spectral modeling and the main results, Section 4 discusses the further implications of the results, and Section 5 gives a brief summary
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