Infrared photometry of SN 1987A.

The authors present infrared (1 μm - 14 μm) photometric and spectroscopic observations of SN 1987A obtained at ESO La Silla between February 28 and March 16, 1987. A preliminary interpretation of the photometry suggests an expanding photosphere with T_eff decreasing from 5800K on March 1, to 5200K on March 11; adopting a distance of 55 kpc, the luminosity increased from 3.2 to 5.5×10⁷L_sun;, and the effective radius from 5600 to 9100 solar radii. No significant excess could yet be detected longward on the L band filter. The spectrum is dominated by hydrogen emission lines whose intensities and shapes vary on timescales as short as one day. Some of these lines show P-Cygni profiles, indicative of expansion velocities of 6000 - 10000 km/s.