IMAPS Observations of the ISM Toward Gamma Cassiopeiae

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Session 12 -- Interstellar medium
Display presentation, Monday, 9, 1995, 9:20am - 6:30pm

[12.05] IMAPS Observations of the ISM Toward Gamma Cassiopeiae

G. Sonneborn (NASA/GSFC), U. J. Sofia (NASA/GSFC, NRC), E. B. Jenkins (Princeton Univ. Obs.)

The interstellar medium on the line of sight toward $\gamma$ Cassiopeiae was observed in the 950-1150\AA\ region at a resolving power of $\sim200,000$ by the Interstellar Medium Absorption Profile Spectrograph (IMAPS) as part of the ORFEUS-SPAS space shuttle flight in September 1993. The $\gamma$ Cas sightline was previously studied with the Copernicus satellite (see Ferlet et al. 1980, ApJ, 242, 576) where a four-component structure was derived ($V_{LSR} = -24.6, -17.1, -7.8, 1.3$ km/sec). However, at the Copernicus resolution of 15 km/sec this velocity structure was somewhat uncertain and several ambiguities remain. With the higher resolution of IMAPS ($\sim2$ km/sec) it is now possible to address some of the longstanding questions about the complex velocity structure of this sightline. This paper presents an analysis of several atomic lines (e.g. C II 1036-37, N I 1134-35, N II 1084-85, Ar I 1048, 1066, P II 1124, 1152) and lines of the H$_2$ Lyman bands. The velocity structure and column densities are compared with the Copernicus results.

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