ULTRAVIOLET OBSERVATIONS OF SN 1987A WITH THE IUE SATELLITE

Ultraviolet (lambda: 1150-3300 Angstrom) observations of SN 1987A with the IUE satellite provide a unique data set. Observations started the day after discovery, 1987 February 24 (day 1.6), and a total of 751 spectra were obtained through 1992 June 9 (day 1567). The data have been processed to generate a complete catalog of SN 1987A ultraviolet spectra. The data reduction procedure includes careful line-by-line extraction, removing hits and hot pixels, and, most importantly, a scrupulous subtraction of the contribution from stars near SN 1987A within the IUE aperture. In addition to processing the data, we have also extracted light curves, and combined them with the ground-based optical data and HST observations (day 1278 to 2431) to extend the study in both wavelength and time. The data-processing procedures of our IUE study produce results that are consistent with the HST data where they overlap, but not with the IUE study by Sanz Fernandez de Cordoba (1993) because of its incorrect background subtraction. The IUE data are consistent with the ground-based Walraven VBLUW photometry, while we found that flux scale of the Soviet ASTRON satellite spectroscopic data is low by similar to 15%. The UV flux plummeted during the earliest days of observations because of the drop in the photospheric temperature and the increase in opacity. However, after reaching a minimum of 0.04% on day 44, the UV flux increased by 175 times in its contribution to 7% of the total UVOIR bolometric luminosity at day 800. A revised set of bolometric data has been constructed which includes the contribution of UV from day 1 to day 1352. Studies of the UV colors show that the supernova started to get bluer in UV around the time when dust started to form in the ejecta. Our results are consistent with the possibility that the dust condensed may be metal-rich.