X-Ray Detection of Presupernova Evolution for the SN 1993J Progenitor
Abstract
We report on the first detection of presupernova evolution in the X-ray regime. The results are based on ROSAT observations of SN 1993J ranging from 6 days to 5 years after the outburst. The X-ray observations are used to probe the SN shell interaction with the ambient circumstellar matter (CSM). After exploring various scenarios that might explain the observed X-ray light curve with a t-0.27 rate of decline, we present a coherent picture in terms of the interaction of the SN shock front with the CSM deposited by the progenitor's stellar wind. During the observed period, the SN shell reaches a radius of 3×1017 cm from the site of the explosion, corresponding to ~104 yr in the progenitor's stellar wind history. Our analysis shows that the mass-loss rate of the progenitor has decreased constantly from M=4×10-4 to 4×10-5 Msolar yr-1 (vw/10 km s-1) during the late stage of the evolution. Assuming a spherically symmetric expansion, the circumstellar matter density profile is found to be significantly flatter (ρcsm~r-1.63) than expected for a constant mass-loss rate and constant wind velocity profile (r-2). The observed evolution reflects a decrease in the mass-loss rate, an increase in the wind speed, or a combination of both, indicating that the progenitor likely was making a transition from the red to the blue supergiant phase during the late stage of its evolution.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- November 2001
- DOI:
- 10.1086/324407
- arXiv:
- arXiv:astro-ph/0109212
- Bibcode:
- 2001ApJ...561L.107I
- Keywords:
-
- Stars: Mass Loss;
- X-rays: individual (SN 1993J);
- X-Rays: ISM;
- Astrophysics
- E-Print:
- 5 pages, 3 figures, accepted for publication in the Astrophysical Journal Letters