The spectra of SN.

Abstract

Absolute spectral-energy distributions have been obtained for a number of supernovae of Types I and II. Included is a comprehensive set of observations, spanning 230 days of the bright Type I supernova 1972e in NGC 5253. Three general conclusions are reached: (1) Both SN I's and SN II's have a continuum which changes slowly and uniformly with time and which carries the bulk of the radiated flux. (2) There exist lines in both SN l's and SN II's which have P Cygni profiles, i.e., broad emissions flanked on their violet edges by broad absorptions. (3) Lines exist which persist through the evolution of the spectrum and which are common to SN I's and SN II's. In SN II's, spectral lines are identified as Ha, H , Hy, H and K of Ca tt, the infrared triplet at A8600 of Ca ii, the sodium D-lines, the magnesium b-lines at ASi 80, and possibly also Fe it lines. At late stages the [0 t] lines AA6300, 6363, and a line which is tentatively identified as a blend of the [Ca it] lines AA7291, 7323 is also observed. In SN I's spectral lines are identified as H and K of Ca it, the infrared triplet of Ca it, the sodium D-lines, and the magnesium b-lines. Some two weeks after maximum there is evidence that Ha and Hy may appear. The H line is in a confused spectral region and its presence cannot be verified. The strong A4600 feature gradually drifts with time from 4600 A near maximum light to 4700 A after 250 days. When it is near 4600 A it may be a blend of Fe it lines; when it reaches 4700 A it perhaps should be identified with the He it line at A4686. The two SN II's observed have expansion velocities in the outermost regions of 15,000 km -i, while that of the SN I 1972e in NGC 5253 has 20,000 km -1 In the case of SN II's, some weeks after maximum light the photospheric temperature is about 5000 K and the electron density in the "reversing layer" is approximately 1 0 electrons cm -3. The dilution factor at this time is approximately 10- . The number of electrons per cm2 in the line of sight appears to be approximately 1024 which suggests that electron scattering is the main source of opacity. It is suggested that the chemical abundances in SN II's may be approximately solar while hydrogen may be very deficient in SN I's. Subject headings: abundances, stellar - line identifications - supernovae