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Session 17 - ISM, Star Formation & Planets.
Oral session, Monday, June 09
North Main Hall C/D,
The UV spectrum of the Red Rectangle and its central source, HD 44179, was examined using the Goddard High Resolution Spectrograph (GHRS) of the Hubble Space Telescope (HST). Spectra have been obtained of the 0-0, 0-1, and 0-2 vibronic bands of the CO fourth positive system, the 1657 Å\ C I multiplet, and the 1931 Å\ C I line. All of the lines and bands display both absorption and emission components. The components do not display P Cygni profiles, but are nearly symmetrically reversed and show different spreads of radial velocity. The widths and Doppler shifts of each component provide information about the environment of origin, as do the rotational and vibrational distibutions in CO.
The 1657 Å\ multiplet is too complex for analysis, but the 1931 Å\ line can be deconvolved into two components: emission with a narrow velocity dispersion, 25 km/s, and absorption with a broad velocity dispersion, 230 km/s. For the CO bands we obtained a best fit from a four component model, consistent for all three bands. The four components are as follows: two emission components with narrow velocity spreads (29 km/s), one with rotational temperature of 50 K the other about 3000 K; a third emission component with a very wide velocity spread (600 km/s) and rotational temperature of about 100K; and an absorption component with a wide velocity spread (230 km/s) and rotational temperature of about 100 K. The high temperature emission displayed partially resolved rotational line structure corresponding to levels of J > 50.
Our previous observation (1996, ApJ, 467, L109) of the spin-forbidden CO Cameron bands in this object, also suggests that there is an environment where CO is being excited by charged particle impact. We discuss these observations with respect to the accretion disk model of this object. We also compare our UV CO observations with the work of others on the IR CO overtone spectra in YSOs.
Program listing for Monday