AAS 200th meeting, Albuquerque, NM, June 2002
Session 73. Interim Stellar Materials: Gas, Dust and Clouds
Display, Thursday, June 6, 2002, 9:20am-4:00pm, SW Exhibit Hall

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[73.14] High-Ionization Gas Associated with a Supershell Surrounding the Perseus OB1 Association

D. C. Knauth, J. C. Howk (Johns Hopkins), K. R. Sembach (STScI), J. T. Lauroesch, D. M. Meyer (Northwestern)

We present Far-Ultraviolet Spectroscopic Explorer (FUSE) and Space Telescope Imaging Spectrograph (STIS) observations of high-ionization interstellar absorption toward HD~14434, an O5.5 V star in the Per OB1 Association. This star lies in the direction of the H~{\small I} supershell GS139-03-69 (Heiles 1979, ApJ, 229, 533). In addition, a supershell-like bubble is detected from WHAM maps of the Perseus arm (Madsen, Haffner, & Reynolds astro-ph/0112232). We detect intermediate velocity interstellar Si~{\small IV} and C~{\small IV} absorption centered at VLSR = -73~km~s-1, while low-ionization Perseus arm gas is detected at approximately -50 km s-1. Neither N~{\small V} nor O~{\small VI} is detected at these velocities, although Fe~{\small III}, a tracer of warm ionized gas, is seen. The column densities in the -73~km~s-1 component are \log N({\rm C~{\small IV}})~=~13.93 ± 0.02, \log N({\rm Si~{\small IV}})~=~13.35 ± 0.02, \log N({\rm N~{\small V}}) \leq 12.65, and \log N({\rm O~{\small VI}}) \leq 13.32. The observed C~{\small IV}/Si~{\small IV} ratio of 3.8 ± 0.3 is similar to the Galactic average. Analysis of the C~{\small IV} and Si~{\small IV} line widths yields a temperature of T ~ 12,000~K for this component. No C~{\small IV} or Si~{\small IV} is produced via collisions at such low temperatures. We explore two models for the origins of the intermediate velocity C~{\small IV} and Si~{\small IV} absorption: photoionization or non-equilibrium collisional processes. Either of these could be related to the origins of the high-ionization gas with a supershell.

This work is based on data obtained for the Guaranteed Time Team by the NASA-CNES-CSA FUSE mission. Financial support has been provided by NASA contract NAS5-32985.

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Bulletin of the American Astronomical Society, 34
© 2002. The American Astronomical Soceity.