Session 99 - Supernovae & Supernova Remnants.
Oral session, Friday, January 09
Lincoln,

## [99.01] Studies of the SN 1987A Debris with HST\/ Observations

C. S. J. Pun (NASA/GSFC, AURA/NOAO), R. P. Kirshner, P. M. Garnavich, P. Challis (CfA-Harvard)

The HST\/ observations of Supernova 1987A provide for the first time information on the shape and expansion of a late time supernova atmosphere. The photometric and spectroscopic evolution of Supernova 1987A have been continuously monitored by the Supernova INtensive Study (SINS) collaboration which cover a span of 7 years (1990 August --- 1997 July). The supernova debris is resolved in the HST\/ image and its size can be directly measured. The debris profile is fitted with a brightness function derived from the spectroscopic data. The debris has a diameter of \sim 0\hbox.\!\!^\prime\prime2 and it expands homologously at \sim 2800 km s^-1 at all wavebands. The measured velocity reflects that of the radioactive Fe core materials and suggests severe mixing in the supernova envelope. With the post service mission images, the shape and asymmetry of the debris can also be studied. The measured major to minor axes ratio of the debris is \sim 1.15 --- 1.20, with the major axis nearly aligned with the axis of the circumstellar ring system. With the last set of images taken in 1997 July (day 3791), small scale structures can be identified in the SN 1987A debris. The observed structure is consistent with a model with clumps of materials ejected above and below the plane of the circumstellar ring. Detailed studies of the shape of the debris provide additional constraints on the progenitor models and explosion dynamics of the supernova.