THE ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES, 99:223-261, 1995 July

          ULTRAVIOLET OBSERVATIONS OF SN 1987A WITH THE IUE SATELLITE

                     CHUN S.J. PUN AND ROBERT P. KIRSHNER
        Harvard-Smithsonian Center for Astrophysics, 60 Garden Street,
                              Cambridge, MA 02138

                               GEORGE SONNEBORN
   Laboratory for Astronomy and Solar Physics, Code 681, NASA/Goddard Space
                      Flight Center, Greenbelt, MD 20771

                     PETER CHALLIS AND GEORGE NASSIOPOULOS
        Harvard-Smithsonian Center for Astrophysics, 60 Garden Street,
                              Cambridge, MA 02138

     RICHARD ARQUILLA, D. MICHAEL CRENSHAW, CHRIS SHRADER, AND TERRY TEAYS
    Computer Sciences Corporation, NASA/GSFC Code 681, Greenbelt, MD 20771

  ANGELO CASSATELLA, ROBERTO GILMOZZI, ANTONIO TALAVERA, AND WILLEM WAMSTEKER
           ESA IUE Observatory, VILSPA, Villafranca, Apartado 50727,
                             E-28080 Madrid, Spain

                                CLAUS FRANSSON
             Stockholm Observatory, S-133 36 Saltsjobaden, Sweden

                                      AND

                                 NINO PANAGIA
           Space Telescope Science Institute, 3700 San Martin Drive,
                              Baltimore, MD 21218


                                   ABSTRACT

        Ultraviolet (lambda: 1150-3300 A) 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, A&A, 276, 103) 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 ~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.

     Subject headings: ultraviolet: stars -- stars: individual (SN 1987A)