AAS 195th Meeting, January 2000
Session 43. SN 1987A and Other Supernova Remnants
Display, Thursday, January 13, 2000, 9:20am-6:30pm, Grand Hall

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[43.04] HST Spectroscopy of a Brightening Spot on the Circumstellar Ring of SN~1987A

C.S.J. Pun, G. Sonneborn, S. Maran (NASA-GSFC), E. Michael, R. McCray, S. Zhekov (JILA), R.P. Kirshner, P.M. Garnavich, P. Challis (CfA), SINS Collaboration

We present HST\//STIS spectroscopy of the bright spot near the inner circumstellar ring of the Supernova 1987A. Ultraviolet and optical spectra covering a wavelength range 1150~-- 10000~Å\ were obtained. The spot is brightening fast~--- \ion{N}{5}~\lambda\lambda 1239, 1243 emission increases by a factor of 5.4 from 1997.7 to 1999.7. Emission of this brightening spot is likely to be produced by the shock interaction between the supernova blast wave and the dense gas in the ring. A large number of emission lines of various ionization stages (for example, H, He~{\sc i}--{\sc ii}, N~{\sc i}--{\sc v}, O~{\sc i}--{\sc iv}, S~{\sc ii}--{\sc iii}) are observed. The FWHM width of the optical emission lines at \ga 250~{\rm km \ s}-1 indicates the presence of a radiative shock travelling into the dense (n > 104 \ \rm{cm}2) gas of the circumstellar ring. The strong \ion{N}{5} emission observed suggest that the post-shock temperature is high (T ~106~K). Preliminary shock calculations with a plane-parallel steady-state shock running into a spherical/conical ring protrusion do not provide a good fit to the observed spectrum and we discuss possible explanations for the discrepency.

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.

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The author(s) of this abstract have provided an email address for comments about the abstract: pun@congee.gsfc.nasa.gov

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