Computer Science
Scientific paper
Dec 2002
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2002phdt........20m&link_type=abstract
Thesis (PhD). UNIVERSITY OF COLORADO AT BOULDER, Source DAI-B 63/06, p. 2874, Dec 2002, 195 pages.
Computer Science
5
Scientific paper
We investigate emission observed from Supernova Remnant (SNR) 1987A and develop theoretical models to explain its origin. The supernova (SN) progenitor was surrounded by an equatorial ring of gas which was illuminated by the SN's initial flash of ionizing radiation. As the SN ejecta expands into this circumstellar gas a double-shock structure forms, consisting of a blast wave which propagates into the circumstellar material and a reverse- shock front which propagates back into the SN ejecta. We establish that the brightening emission observed from SNR 1987A is created by these shock fronts. We interpret Hubble Space Telescope (HST) observations of the optical and ultraviolet spectra of the first brightening spot on the equatorial ring. This spot marks the location of radiative shocks created where the blast wave has impacted dense gas protruding inward from the ring. The observed line widths indicate that only shocks with velocities <250 km s-1 have become radiative, while line ratios indicate that much of the emission must come from slower ( ≲ 135 km s-1) shocks. We discuss the X-ray emission observed from SNR 1987A with the Chandra X-ray Observatory. The X-ray spectra are well fit by plane-parallel shock models with post-shock electron temperatures of ≈2.6 keV and ionization ages of ≈6 × 1010 cm-3 s, characteristic parameters of the shocked plasma behind the blast wave. The X-ray line profile has a width of ≈5000 km s-1, indicating a blast-wave velocity of ≈3500 km s-1 (mean post-shock temperature of ≈17 keV). This is direct evidence for incomplete electron-ion temperature equilibration behind the blast wave. We present line profiles of high-velocity Lyα and Hα emission from SNR 1987A obtained with HST. This emission comes from hydrogen in the ejecta which passes through the reverse shock. The observed emission is confined within ≈±30° about the equatorial plane and has a radius of ≈75% of the distance to the ring. The measured reverse-shock geometry is consistent with the expansion of the ejecta into a bipolar hourglass-shaped nebula. We determine the expansion rate of the reverse-shock surface to be 3600 ± 900 km s-1 from the reverse-shock's light curve.
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