We report far-infrared and submillimeter observations of supernova 1987A, the star whose explosion was observed on 23 February 1987 in the Large Magellanic Cloud, a galaxy located 160,000 light years away. The observations reveal the presence of a population of cold dust grains radiating with a temperature of about 17 to 23 kelvin at a rate of about 220 times the luminosity of the Sun. The intensity and spectral energy distribution of the emission suggest a dust mass of about 0.4 to 0.7 times the mass of the Sun. The radiation must originate from the supernova ejecta and requires the efficient precipitation of all refractory material into dust. Our observations imply that supernovae can produce the large dust masses detected in young galaxies at very high redshifts.

The radio and X-ray observations of SN 1993J during the rst year can be consistently explained as a result of interaction of the expanding ejecta with a circumstellar medium. The density of the circumstellar gas can be deduced from the free-free absorption of the radio emission and from the X-ray luminosity. During the rst two weeks, both sets of observations indicate a mass loss rate of 4 10 5 M yr 1 for a wind velocity of 10 km s 1 . The subsequent radio and X-ray observations indicate a density gradient / r s , with 1:5 < s < 1:7, as opposed to the Subject headings: circumstellar matter { -rays: general { radio: general { supernovae: individual (SN 1993J) { X-rays: general

The optical/UV light curves of SN 1987A are analyzed with the multienergy group radiation hydrodynamics code STELLA. The calculated monochromatic and bolometric light curves are compared with observations shortly after shock breakout, during the early plateau, through the broad second maximum, and during the earliest phase of the radioactive tail. We have concentrated on a progenitor model calculated by Nomoto & Hashimoto and Saio, Nomoto, & Kato, which assumes that 14 of the stellar M _ mass is ejected. Using this model, we have updated constraints on the explosion energy and the extent of mixing in the ejecta. In particular, we determine the most likely range of E/M (explosion energy over ejecta mass) and (radius of the progenitor). In general, our best models have energies in the range R 0 E \ (1.1^0.3) ] 1051 ergs, and the agreement is better than in earlier, Ñux-limited di †usion calculations for the same explosion energy. Our modeled B and V Ñuxes compare well with observations, while the Ñux in U undershoots after D10 days by a factor of a few, presumably owing to NLTE and line transfer e †ects. We also compare our results with IUE observations, and a very good quantitative agreement is found for the Ðrst days, and for one IUE band (2500È3000 as long as for 3 months. We point out A ) that the V Ñux estimated by McNaught & Zoltowski should probably be revised to a lower value.

High-quality spectropolarimetry (range 417-860 nm; spectral resolution 1.27 nm and 0.265 nm/pixel) of the SN Ia 2001el were obtained with the ESO Very Large Telescope Melipal (+ FORS1) at 5 epochs. The spectra a week before maximum and around maximum indicate photospheric expansion velocities of about 10,000 km s −1 . Prior to optical maximum, the linear polarization of the continuum was ≈ 0.2 − 0.3% with a constant position angle, showing that SN 2001el has a well-defined axis of symmetry. The polarization was nearly undetectable a week after optical maximum.The spectra are similar to those of the normally-bright SN 1994D with the exception of a strong double-troughed absorption feature seen around 800 nm (FWHM about 22 nm). The 800 nm feature is probably due to the Ca II IR triplet at very high velocities (20,000 -26,000 km s −1 ) involving ∼ 0.004 M ⊙ of calcium and perhaps 0.1 M ⊙ total mass. The 800 nm feature is distinct in velocity space from the photospheric Ca II IR triplet and has a significantly higher