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B.E. Sugerman, S.S. Lawrence (Columbia University), P. Bouchet (CTIO), A.P.S. Crotts (Columbia University), S.R. Heathcote (CTIO)
As the interaction (hot spots) between the ejecta from SN 1987A and its circumstellar equatorial ring (ER) intensifies, this region will undergo radical changes, providing an unprecedented opportunity to observe, at high spatial, spectral and temporal resolution, the birth of a supernova remnant. We report results from continued study of the ER using new and archival HST WFPC2 and STIS data (including the most recent STIS data taken of the SNR from May 2001), as well as ground-based monitoring from the CTIO 4-m Tip-Tilt with first order wavefront correction in near-IR lines.
Ground-based data from March 2001 reveals the continuing brightening of the first seven known spots in \ion{He}{1}~1.083\mum and the appearance of at least the first three spots in P\beta. Difference imaging (Tomaney & Crotts 1996) of HST data between 2000 and 1999 reveals the probable appearance of two additional hot spots along the western half of the ER, bringing the total count to at least 11. A detailed study of the ER geometry and hot spot positions suggests that the ring may be intrinsically ellipsoidal, that significant inhomogeneity exists in the ejecta outflow on large and small scales, and may explain the early appearance of the first spot. We study the temporal evolution of these spots, which can reveal information about the structure of the ER and shocks on spatial scales smaller than the imaging resolution of HST, by constructing multi-wavelength lightcurves for the first seven spots. We find that different spots do not vary uniformly, but appear to brighten more rapidly if located on protrusions from the inner ER with high-flux gradients. Also, the first hot spot appears to be advancing to a new stage of evolution as its lightcurve turns over.
This research was supported by NASA grant NAG5-3502 and STScI grants GO 8806 and GO 8872.