New Hubble Space Telescope observations of high-velocity Lyα and Hα in SNR 1987A

We describe and model high-velocity (approximate to 15,000 km s(-1)) Ly alpha and H alpha emission from the supernova remnant SNR 1987A seen in 1997 September and October with the Space Telescope Imaging Spectrograph. Part of this emission comes from a reverse shock located at approximate to 75% of the radius of the inner boundary of the inner circumstellar ring and confined within +/- 30 degrees of the equatorial plane. Departure from axisymmetry in the Ly alpha and H alpha emission correlates with that seen in nonthermal radio emission and reveals an asymmetry in the circumstellar gas distribution. We also see diffuse high-velocity Ly alpha emission from supernova debris inside the reverse shock that may be due to excitation by nonthermal particles accelerated by the shock.