New spectroscopic data obtained on SNR candidates and H II regions in M31 are used to confirm the SNR diagnostic and to derive abundances. With all data available in the literature, confirmation is obtained for 12 SNR from a detailed study of some characteristic line ratios. In the absence of a direct temperature determination for the H II regions and the SNR, empirical methods are used to derive oxygen and nitrogen abundances. While N/H and N/O gradients are present with values comparable to the ones found in our Galaxy, no evidence exists for one in oxygen, in view of the large uncertainties in the abundance determinations. The SN rate is found to be about one in 200 yr, at variance with the higher rate (one every 40 yr) found from SN statistics. The difference between the two determinations is found to be smaller in M33.
No takes yet. Share an insight, caveat, or question.
Dennefeld et al. (1981) studied this question.