Type Ib supernovae 1983n and 1985f - Oxygen-rich late time spectra

Abstract

Spectroscopic observations of SN 1983n obtained on February 28 and March 1, 1984 (8 mo after maximum light) and of SN 1985f obtained on March 25, 1985 (25 d after discovery), both using the IDS spectrograph on the 2.7-m telescope at McDonald Observatory, are reported and analyzed. The spectra are presented graphically and compared. The spectra of SN 1983n exhibit broad emission lines including the forbidden lines of O I at 6300 and 6364 A and of Ca II at 7291 and 7324 A, the lines of Na I at 5890 and 5896 A, and the semiforbidden line of Mg I at 4562 A. Very similar features are found in the spectrum of SN 1985f, in agreement with the observations of the discoverers (Filippenko and Sargent, 1985), suggesting that both objects are SN of type Ib. From the evidence of H deficiency and the presence of O, circumstellar nebulae, and associated H II regions it is inferred that the progenitors of type Ib SN may be Wolf-Rayet stars.