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arXiv · astro-ph/9710373

Spatially Resolved STIS Spectroscopy of SN 1987A: Evidence for Shock Interaction with Circumstellar Gas

Abstract

Visual and ultraviolet spatially resolved (~ 0."1) spectra of SN 1987A obtained on days 3715 and 3743 with the Space Telescope Imaging Spectrograph on the Hubble Space Telescope show that the high-velocity SN debris is colliding with circumstellar gas. Very broad Ly-alpha emission with velocities extending to ~ +/- 20,000 km/s originates inside the inner circumstellar ring and appears to fill most of the surface area within 0."67 +/- 0."03 (0.14 pc at a distance of 50 kpc) of the ring's center. The observed Ly-alpha flux from the shocked ejecta is (1.85 +/- 0.53) 10^{-13} erg/cm2/s and (1.25 +/- 0.51) 10^{-12} erg/cm2/s after correcting for extinction. A spatially unresolved blue-shifted emission feature was discovered in H-alpha (and other lines) on the inner ring at p.a. 31 +/- 8 degree. The H-alpha emission extends to -250 km/s with no corresponding red-shifted emission. This highly localized interaction appears to be the initial contact of the supernova blast wave with an inward protrusion of the inner ring. The broad Ly-alpha emission and the `hot spot' are separate interaction phemonena associated with the reverse and forward shocks, respectively. We also find that the size of the inner ring in forbidden lines of oxygen has a dependence on ionization potential, in agreement with photoionization models of the ring.

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G. Sonneborn, C. S. J. Pun, R. A. Kimble, T. R. Gull, P. Lundqvist, R. McCray, P. Plait, A. Boggess, C. W. Bowers, A. C. Danks, J. Grady, S. R. Heap, S. Kraemer, D. Lindler, J. Loiacono, S. P. Maran, H. W. Moos, B. E. Woodgate. 1997-10-31. Spatially Resolved STIS Spectroscopy of SN 1987A: Evidence for Shock Interaction with Circumstellar Gas. https://doi.org/10.1086/311106

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