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C.S.J. Pun (NASA's GSFC, AURA/NOAO), G. Sonneborn (NASA's GSFC), P. Lundqvist (Stockholm Obs.), R. McCray, E. Michael, S. Zhekov (JILA), R.P. Kirshner (CfA), SINS collaboration
We present HST\//STIS spectroscopy of some new bright spots (spots 2-4) near the inner circumstellar ring of the Supernova 1987A. Medium resolution (\Delta v ~50~{\rm km \ s}-1) spectra covering a wavelength range 6295-6867~Å\ were obtained. Emissions of these brightening spots are likely to be produced by the shock interaction between the supernova blast wave and the dense gas in the ring. Emission line profiles of a few lines, including H\alpha, [\ion{O}{1}] \lambda\lambda6300, 6364, and [\ion{N}{2}] \lambda\lambda6548, 6583, are obtained.
The results of the new spots are compared with those from the first hotspot which appeared about 2 years before the new ones (Michael et al. 2000, ApJ, 542, L53). The new spots have similar line profile shapes and widths (v\rm FWHM ~200~{\rm km \ s}-1) as that of spot~1. The emission from the new spots, located on the far side of the ring, all peak at ~+50~{\rm km \ s}-1 whereas the emission from spot~1, located on the near side of the ring, peaks at ~-50~{\rm km \ s}-1. Moreover, the observed line ratios, [\ion{N}{2}]/H\alpha, and [\ion{O}{1}]/H\alpha, vary by a factor of ~3 between the spots, suggesting different physical conditions in the line forming regions. The constraints on the geometry of the shock structure will also be discussed.
Support for this work is provided by NASA through grant GO-08243 from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. C.S.J.P. acknowledges support by the STIS IDT through AURA/NOAO by NASA.