Observations of Far-uv Absorption Lines at 2 km/s Resolution with IMAPS

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Session 65 -- The Galaxy and Galactic ISM
Oral presentation, Thursday, 2, 1994, 10:00-11:30

[65.05] Observations of Far-uv Absorption Lines at 2 km/s Resolution with IMAPS

E.B.Jenkins, P.M.Zucchino, M.A.Reale (Princeton U. Obs.), C.L.Joseph (U. Wisc.), G.Sonneborn, R.S.Polidan (GSFC), T. Williams (Rutgers U.)

The Interstellar Medium Absorption Profile Spectrograph (IMAPS) flew on the ORFEUS-Spas mission that was launched on STS-51 in September, 1993 for a joint science program sponsored by the US and German space agencies, NASA and DARA. IMAPS is an objective-grating echelle spectrograph that records the spectra of bright stars in the wavelength region 950$-$1150\AA\ at a resolution of 1 to 2 km ${\rm s}^{-1}$. The central objective of IMAPS is to study the interstellar lines of ${\rm H}_2$ and some key atomic species, but it is also useful for observing stellar phenomena.

The following stars were observed: $\gamma$ Cas, $\alpha$ Eri, $\epsilon$ Ori, $\zeta$ Ori, $\kappa$ Ori, $\zeta$ Pup, $\gamma^2$ Vel, $\beta$ Cru, $\eta$ UMa, and $\beta$ Cen A. Data processing is still underway, but we present some preliminary results, in particular, well resolved velocity components of ${\rm H}_2$ toward $\epsilon$ and $\zeta$ Ori. In $\zeta$ Ori, ${\rm H}_2$ at a heliocentric velocity $v_{\sun} \approx -2$ km ${\rm s}^{-1}$ shows pronounced changes in width for different rotational quantum numbers $J$, and ionized gas shown by the strong features of C~II and N~II can be seen over the velocity ranges $-95 < v_{\sun} < -70$ and $-45 < v_{\sun} < +50$ km ${\rm s}^{-1}$.

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