The Spectroscopic and Photometric Evolution of Type II Supernovae

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Session 19 -- Supernovae and SNRs
Oral presentation, Monday, 2:30-4:00, Zellerbach Auditorium Room

[19.02] The Spectroscopic and Photometric Evolution of Type II Supernovae

A.V.Filippenko (UC Berkeley)

The spectral evolution of several Type II supernovae will be illustrated and discussed. These include SNe 1988Z, 1990H, 1992H, 1993G, and 1993J. Possible correlations with light curves will be mentioned.

SN 1988Z, for example, had a very extended light curve with a fairly linear decline, a blue continuum, and Balmer emission lines with essentially no evidence for blueshifted absorption. The peculiar properties of SN 1988Z were probably caused, in part, by the interaction of the ejecta with a dense circumstellar medium. Direct evidence for dense gas ($n_e \approx 10^7$ cm$^{-3}$) comes from the appearance of narrow [O~III] emission lines in the early-time spectrum; the intensity ratio of [O~III] $\lambda$4363 to [O~III] $\lambda$5007 is too high to be consistent with a significantly lower density, regardless of the electron temperature.

SNe 1990H and 1992H, by contrast, had classical ``plateau'' light curves. Their spectra became red very rapidly and exhibited Balmer lines with prominent P Cygni profiles. Narrow emission lines produced by ionized circumstellar gas were weak or absent in these objects. Thus, it appears as though interaction with a circumstellar wind does not play as important a role in typical Type II-plateua supernovae, at least during the early stages of their evolution.

The spectra and light curves of two very recent Type II SNe, 1993G and 1993J, will be compared with those of the above SNe II. At the time this abstract was submitted, it appeared as though SN 1993G and probably SN 1993J are of the Type II-plateau variety. On the other hand, there is significant evidence for the presence of circumstellar gas in the early-time spectrum of SN 1993J, so it is possible that its light curve will exhibit some of the properties of the Type II-linear or peculiar Type II (e.g., SN 1988Z) subclasses.

Monday program listing