Ramakrishnan Vandana, Dwarkadas Vikram V
Department of Astronomy and Astrophysics, University of Chicago 5640 S Ellis Avenue, Chicago, IL 60637, USA.
Current Address: Department of Physics and Astronomy, Purdue University 525 Northwestern Avenue, West Lafayette, IN 47907, USA.
Astrophys J. 2020 Oct 1;901(2). doi: 10.3847/1538-4357/abb087. Epub 2020 Sep 29.
Core-collapse supernovae (SNe) expand into a medium created by winds from the pre-SN progenitor. The SN explosion and resulting shock wave(s) heat up the surrounding plasma, giving rise to thermal X-ray emission, which depends on the density of the emitting material. Tracking the variation of the X-ray luminosity over long periods of time thus allows for investigation of the kinematics of the SN shock waves, the structure of the surrounding medium, and the nature of the progenitor star. In this paper, X-ray observations of five of the oldest known X-ray SNe-SN 1970G, SN 1968D, SN 1959D, SN 1957D, and SN 1941C-are analyzed, with the aim of reconstructing their light curves over several decades. For those SNe for which we can extract multiepoch data, the X-ray luminosity appears to decline with time, although with large error bars. No increase in the X-ray emission from SN 1970G is found at later epochs, contrary to previous reports. All five SNe show X-ray luminosities that are of comparable magnitude. We compare the late-time X-ray luminosities of these SNe to those of supernova remnants (SNRs) in the Galaxy, which are a few hundred years old, and find that when the tentative decline is taken into account, the luminosity of the old SNe studied herein could fall below the luminosity of some of the younger SNRs within a few hundred years. However, the X-ray luminosity should begin to increase as the SNe expand in the Sedov phase, thus reaching that of the observed SNRs.
核心坍缩超新星（SNe）会膨胀进入由超新星前身恒星的星风所形成的介质中。超新星爆发以及产生的激波会加热周围的等离子体，从而产生热X射线辐射，这种辐射取决于发射物质的密度。因此，长时间追踪X射线光度的变化有助于研究超新星激波的运动学、周围介质的结构以及前身恒星的性质。在本文中，我们分析了五颗已知最古老的X射线超新星——SN 1970G、SN 1968D、SN 1959D、SN 1957D和SN 1941C——的X射线观测数据，目的是重建它们在几十年间的光变曲线。对于那些我们能够提取多历元数据的超新星，尽管误差条较大，但X射线光度似乎随时间下降。与之前的报告相反，在后期没有发现SN 1970G的X射线辐射增加。所有五颗超新星的X射线光度量级相当。我们将这些超新星的晚期X射线光度与银河系中已有几百年历史的超新星遗迹（SNRs）的进行比较，发现如果考虑到这种初步下降，本文所研究的古老超新星的光度可能在几百年内低于一些较年轻的超新星遗迹的光度。然而，随着超新星在塞多夫阶段膨胀，X射线光度应该会开始增加，从而达到观测到的超新星遗迹的光度。
