A postmortem investigation of the Type IIb supernova 2001ig

We present images taken with the GMOS instrument on Gemini-South, in excellent (<0.5 arcsec) seeing, of SN 2001ig in NGC 7424, ~1000 days after explosion. A point source seen at the site of the SN is shown to have colours inconsistent with being an H II region or a SN 1993J-like remnant, but can be matched to a late-B through late-F supergiant with A_V<1. We believe this object is the massive binary companion responsible for periodic modulation in mass loss material around the Wolf-Rayet progenitor which gave rise to significant structure in the SN radio light curve.Comment: 5 pages, 3 figures. Accepted for publication in MNRAS Letters. Fig. 1 resolution degraded to meet size limitations; full resolution version available from http://www.aao.gov.au/local/www/sdr/pubs/sn2001ig_gmos.ps.g

Abundances and density structure of the inner circumstellar ring around SN 1987A

We present optical spectroscopic data of the inner circumstellar ring around SN 1987A from the Anglo-Australian Telescope (AAT) and the Very Large Telescope (VLT) between ~1400 and ~5000 days post-explosion. We also assembled the available optical and near-infrared line fluxes from the literature between ~300 and ~2000 days. These line light curves were fitted with a photoionization model to determine the density structure and the elemental abundances for the inner ring. We found densities ranging from 1x10^3 to 3x10^4 atoms cm^-3 and a total mass of the ionized gas of ~0.058 Msun within the inner ring. Abundances inferred from the optical and near-infrared data were also complemented with estimates of Lundqvist & Fransson (1996) based on ultraviolet lines. This way we found an He/H-ratio (by number of atoms) of 0.17+-0.06 which is roughly 30% lower than previously estimated and twice the solar and the Large Magellanic Cloud (LMC) value. We found an N/O-ratio of 1.5+-0.7, and the total (C+N+O)/(H+He) abundance about 1.6 times its LMC value or roughly 0.6 times the most recent solar value. An iron abundance of 0.20+-0.11 times solar was found which is within the range of the estimates for the LMC. We also present late time (~5000 - 7500 days) line light curves of [O III], [Ne III], [Ne IV], [Ar III], [Ar IV], and [Fe VII] from observations with the VLT. We compared these with model fluxes and found that an additional 10^2 atoms cm^-3 component was required to explain the data of the highest ionization lines. Such low density gas is expected in the H II-region interior to the inner ring which likely extends also to larger radii at higher latitudes (out of the ring plane). At epochs later than ~5000 days our models underproduce the emission of most of these lines as expected due to the contribution from the interaction of the supernova ejecta with the ring.Comment: 17 pages, 8 figures, accepted for publication in Ap

Photometric and Spectroscopic Observations of SN 1990E in NGC 1035: Observational Constraints for Models of Type II Supernovae

We present 126 photometric and 30 spectral observation of SN 1990E spanning from 12 days before B maximum to 600 days past discovery. These observations show that SN 1990E was of type II-P, displaying hydrogen in its spectrum, and the characteristic plateau in its light curve. SN 1990E is one of the few SNe II which has been well observed before maximum light, and we present evidence that this SN was discovered very soon after its explosion. In the earliest spectra we identify, for the first time, several N II lines. We present a new technique for measuring extinction to SNe II based on the evolution of absorption lines, and use this method to estimate the extinction to SN 1990E, Av=1.5+/-0.3 mag. From our photometric data we have constructed a bolometric light curve for SN 1990E and show that, even at the earliest times, the bolometric luminosity was falling rapidly. We use the late-time bolometric light curve to show that SN 1990E trapped a majority of the gamma rays produced by the radioactive decay of 56Co, and estimate that SN 1990E ejected 0.073 Mo of 56Ni, an amount virtually identical to that of SN 1987A. [excerpt