emission lines

emission lines

by Zequn Li -
Number of replies: 0

Spectra of the light echoes (see Fig. 3) show only absorption lines characteristic of cool stellar photospheres, but no evidence of emission lines. In particular, the CaII infrared triplet is only observed as absorption lines in the spectrum.

This seems nuts! This fact is also mentioned in the summary, but I want to talk about this. Why would the light echoes lack emission lines? Surely big explosions should be hot and ionized.