Norberts's Supernova Remnants Page

Overview

X-ray images and medium to low resolution spectra of supernova remnants (SNRs) obtained by a number of X-ray telescopes (onboard EINSTEIN, EXOSAT, ROSAT and ASCA) have revealed a wealth on information on spatial morphology and the underlying X-ray emission. It is now clear that most of the supernova remnants emit thermal radiation form a hot optically thin plama with temperatures in the range of 1 to 10 times 10^6 K. Some show synchrotron emission with a power-law spectrum decreasing with energy. ASCA observed several SNRs with shell-like structures in morphology and thin thermal emission. Here quite a number of lines, especially from heavy elements (Si, S, Fe), indicate that they are not in collisional ionization equilibrium. They are mostly young remnants and the emission seem to consist of a superposition of a reverse shock propagating in the ejecta and a fore shock propagating in the interstellar matter. Examples are Cas-A, Kepler's & Tycho's Remnant.

Typical middle-aged SNRs (age > 10^4 yrs) may show X-ray emission from interstellar matter heated up by the shock wave. Recent observations of one of the schrapnels (A) in the Vel SNR revealed an X-ray spectrum that is dominated by a strong Si-K line.

High resolution X-ray spectroscopy of young and middle aged SNRs will result in more reliable determinations of element abundances and thus refine non-equlibrium thermal emission models. However, although the high spatial resolution of Chandra will result into a greatly improve our perception of the morphology of many SNRs, only a limited number of objects will be available to perform high resolution spectroscopy. Because the high resolution of the grating spectrometer is tightly related to the extend of a source. only SNR or features of SNR that do not extend beyond 20" are feasible for spectroscopic studies. That means, that remnants like Cas A or the Vela SNR are only feasible if they show bright spots in the arcsec domain. However, there are several objects in the LMC and SMC that are, because if their large distance, of quite less extend than galactic remnants and show bright compact rims and spots in their morphology. E0102-72 and N132D are the brightest remnants in the SMC and LMC (respectively) and are the best SNR candidates for grating observations as they are distant enough to subtend a small angular size yet bright enough to allow reasonable integration times. The ASCA spectrum of E0102-72 shows lines of He-like emission from O, Ne, and Mg. The line ratios of these elements cannot be explained using models with uniform abundances. Previous high-resolution studies of N132D using the Einstein Focal Plane Crystal Spectrometer (FPCS) have shown an oxygen overabundance. We plan to use plasma diagnostics of individual emmission lines to map the temperature, ionization and abundance structures of these two remnants:

Determine element abundances and ionization states
Refine Non-equilibrium Models in Young SNRs
Investigate Mosphology and Spectral Evolution in SNRs

High Resolution Spectra of extragalactic Supernova Remnants

TITLE: High resolution spectroscopy of E0102-72 in the SMC

TITLE: High resolution spectroscopy of N132D in the LMC