Raising the Dead: Clues to Type Ia Supernova Physics from the Remnant 0509−67.5

Abstract

We present Chandra X-ray observations of the young supernova remnant (SNR) 0509-67.5 in the Large Magellanic Cloud (LMC), believed to be the product of a Type Ia supernova (SN Ia). The remnant is very round in shape, with a distinct clumpy, shell-like structure that extends to an average radius of 148 (3.6 pc) in the X-ray band. Our Chandra data reveal the remnant to be rich in silicon, sulfur, and iron. The yields of our fits to the global spectrum confirm that 0509-67.5 is the remnant of an SN Ia and show a clear preference for delayed-detonation explosion models for SNe Ia. The Chandra spectra extracted from radial rings are in general quite similar; the most significant variation with radius is a drop in the equivalent widths of the strong emission lines right at the edge of the remnant. We study the spectrum of the single brightest isolated knot in the remnant and find that it is enhanced in iron by a factor of roughly 2 relative to the global remnant abundances. This feature, along with similar knots seen in Tycho's SNR, argues for the presence of modest small-scale composition inhomogeneities in SNe Ia. The presence of both Si and Fe, with abundance ratios that vary from knot to knot, indicates that these came from the transition region between the Si- and Fe-rich zones in the exploded star, possibly as a result of energy input to the ejecta at late times because of the radioactive decay of 56Ni and 56Co. Two cases for the continuum emission from the global spectrum were modeled: one in which the continuum is dominated by hydrogen thermal bremsstrahlung radiation, the other in which the continuum arises from nonthermal synchrotron radiation. The former case requires a relatively large value for the ambient density (~1 cm-3). Another estimate of the ambient density comes from using the shell structure of the remnant in the context of dynamical models. This requires a much lower value for the density (<0.05 cm-3) that is more consistent with other evidence known about 0509-67.5. We therefore conclude that the bulk of the continuum emission from 0509-67.5 has a nonthermal origin.