Ultraviolet Absorption Lines from High-Velocity Gas in the VELA Supernova Remnant: New Insights from Space Telescope Imaging Spectrograph Echelle Observations of HD 72089
Kaiser, Mary Elizabeth; Tripp, Todd M.; Jenkins, Edward B.; Valenti, Jeff A.; Fitzpatrick, Edward L.; Robinson, Richard D.; Kimble, Randy A.; Woodgate, Bruce E.; Danks, Anthony C.; Joseph, Charles L.; Lindler, Don; Bowers, Charles W.; Timothy, J. Gethyn; Beck, Terrence L.; Kraemer, Stephen B.
United States, Canada
Abstract
The star HD 72089 is located behind the Vela supernova remnant and shows a complex array of high- and low-velocity interstellar absorption features arising from shocked clouds. A spectrum of this star was recorded over the wavelength range 1196.4-1397.2 Å at a resolving power of λ/Δλ = 110,000 and a signal-to-noise ratio of 32 by the Space Telescope Imaging Spectrograph on the Hubble Space Telescope. We have identified seven narrow components of C I and have measured their relative populations in excited fine-structure levels. Broader features at heliocentric velocities ranging from -70 to 130 km s-1 are seen in C II, N I, O I, Si II, S II, and Ni II. In the high-velocity components, the unusually low abundances of N I and O I, relative to S II and Si II, suggest that these elements may be preferentially ionized to higher stages by radiation from hot gas immediately behind the shock fronts.
Based on observations with the NASA/ESA Hubble Space Telescope obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy (AURA), Inc., under NASA contract NAS5-26555. The analysis was supported by NASA grant NAG5-30110 to Princeton University.