P. A. Charles
X-ray emission from supernova remnants
1976 (supervisor: J. L. Culhane)

Using data from the Mullard Space Science Laboratory's X-ray telescopes on the satellite OAO-Copernicus, the five supernova remnants, the Crab Nebula, the Cygnus Loop, IC443, Cas A and Pup A, have been studied in detail in the 0.5 - 7.5 keV range. Both spectral and spatial information are available for each remnant, from which the following conclusions may be drawn.

(1) The neutral hydrogen column density in the line of sight to the Crab is 3.1 +/- 0.5 x 10^21 cm^-2. This is at least a factor of 2 above radio (21 cm) determinations of N_H, and methods of resolving the discrepancy are discussed.

(2) The temperature of the Northern and North-Eastern filamentary regions of the Cygnus Loop is 0.17 +/- 0.05 keV, lower than, but within the uncertainties of, earlier measurements. The 0.5 - 1.5 keV X-ray emission from these regions is compared with the results of multiple scan observations which have to be reconstructed. Correlation with the radio structure is established.

(3) The 0.5 - 1.5 keV X-ray emission from IC443 is directly associated with the intense optical filaments. The discrepancy between the filamentary velocity and X-ray shock velocity in this object (and the Cygnus Loop) is examined in the light of the observed spatial distribution of the X-rays.

(4) The spectrum of Cas A is shown to be two-component thermal and this is interpreted in terms of the blast wave model of supernova remnants. Because of the small angular exent of the source, the spatial structure had to be derived using a reconstruction technique (ART) which deconvolved the instrumental response from the data. The results show interesting correlations with the radio shell. The effect of the deconvolution on the results and the level of confidence in them is discussed in detail.

(5) The X-ray spectrum of Pup A is hotter than previously supposed and is fit by an emission line spectrum. A spatial map of the source was also produced with ART showing detailed structure. The possibility of part of the source having a very soft spectrum is examined.