First Results from the Goddard High-Resolution Spectrograph: C i, S i, and CO toward XI Persei and the Physical Conditions in Diffuse Clouds
Ebbets, Dennis C.; Savage, Blair D.; Lambert, David L.; Smith, Andrew M.; Bruhweiler, Frederick C.; Cardelli, Jason A.; Lyu, Cheng-Hsuan; Sheffer, Yaron
United States
Abstract
Observations made by the Goddard High Resolution Spectrograph of the cool, neutral interstellar gas in the line of sight to Xi Per are reported. Heliocentric velocities and equivalent widths were measured for absorption lines of C I and S I. Synthetic spectra were computed and fitted to the observed CO(2-0) and (3-0) bands in the A IPi - X 1Sigma(+) system. Derived populations of the C I ground-state fine-structure levels and the CO ground-state rotational levels were used to derive densities of two of the three, and possibly four, detected cloud components. The velocity component displaying the strongest C I absorption reveals extraordinarily high pressure.