The exceptional X-ray evolution of SN 1996cr in high resolution

Abstract

We present X-ray spectra spanning 18 years of evolution for SN 1996cr, one of the five nearest SNe detected in the modern era. Chandra HETG exposures in 2000, 2004, and 2009 allow us to resolve spectrally the velocity profiles of Ne, Mg, Si, S, and Fe emission lines and monitor their evolution as tracers of the ejecta-circumstellar medium (CSM) interaction. To explain the diversity of X-ray line profiles, we explore several possible geometrical models. Based on the highest signal-to-noise 2009 epoch, we find that a polar geometry with two distinct opening angle configurations and internal obscuration can successfully reproduce all of the observed line profiles. The best fit model consists of two plasma components: (1) a mildly absorbed (2×10 21 cm −2 ), cooler (≈2 keV) with high Ne, Mg, Si, and S abundances associated with a wide polar interaction region (half-opening angle ≈58 • ); (2) a moderately absorbed (2×10 22 cm −2 ), hotter ( > ∼ 20 keV) plasma with high Fe abundances and strong internal obscuration associated with a narrow polar interaction region (half-opening angle ≈20 • ). We extend this model to seven further epochs with lower signal-to-noise ratio and/or lower spectral-resolution between 2000-2018, yielding several interesting trends in absorption, flux, geometry and expansion velocity. We argue that the hotter and colder components are associated with reflected and forward shocks, respectively, at least at later epochs. We discuss the physical implications of our results and plausible explosion scenarios to understand the X-ray data of SN 1996cr.

Seven Years of SN 2014C: A Multiwavelength Synthesis of an Extraordinary Supernova

“…The forward shock interacting with a high-density medium would be the most straightforward explanation for the rise in X-ray emission. On a longer timescale, the contribution to the X-ray flux from the reverse shock may be expected to dominate at some time after the shock has interacted with the dense CSM, as suggested by simulations, and analysis of the emission line profiles, of SN 1996cr (Dwarkadas et al 2010;Quirola-Vásquez et al 2019).…”

X-ray supernova remnants in the starburst region of M 82

“…D.1, also Fig. 4), which is unusual but have been seen in a small number of SNe, such as SN1987A and SN1996cr (Quirola-Vásquez et al 2019;Dwarkadas 2014). Likewise, the flux of the relatively bright Xp5 is rather stable over 16 yr without a sign of declining.…”

“…Compared to SN1993J, the L 2−8 of which dropped below 10 37 erg s −1 after 20 yr (Kundu et al 2019), all our X-ray SNRs have L 4−8 > 10 37 erg s −1 , despite some of their ages, which are known to be >20 yr from radio observations. Since our X-ray SNRs are all embedded in the starbursting molecular disc, the surrounding dense interstellar medium (ISM) could amplify X-ray brightness, as suggested for the X-ray-luminous class of Type IIn SNe (Fox et al 2000;Ofek et al 2013;Chandra et al 2015;Ross & Dwarkadas 2017;Quirola-Vásquez et al 2019).…”

X-ray supernova remnants in the starburst region of M82

“…Compared to SN1993J, the L 2−8 of which dropped below 10 37 erg s −1 after 20 yr (Kundu et al 2019), all our X-ray SNRs have L 4−8 > 10 37 erg s −1 , despite some of their ages, which are known to be > 20 yr from radio observations. Since our X-ray SNRs are all embedded in the starbursting molecular disc, the surrounding dense interstellar medium (ISM) could amplify X-ray brightness, as suggested for the Xray-luminous class of Type IIn SNe (Fox et al 2000;Ofek et al 2013;Chandra et al 2015;Ross & Dwarkadas 2017;Quirola-Vásquez et al 2019).…”