TEMPERATURE AND VELOCITY DIAGNOSTICS OF THE RED RECTANGLE FROM UV SPECTRA OF CO AND C-I

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 Angstrom C I multiplet, and the 1931 Angstrom C I line. All of th e lines and bands display both absorption and emission components. The components do not display P Cygni profiles, but are nearly symmetrica lly reversed and show different spreads of radial velocity. The widths and Doppler shifts of each component provide information about the en vironment of its origin, as do the rotational and vibrational distribu tions in CO. The 1657 Angstrom multiplet is too complex for analysis, but the 1931 Angstrom line can be deconvolved into two components: emi ssion with narrow velocity dispersion, 25 km s(-1), and absorption wit h a broad velocity dispersion, 230 km s(-1). The radial velocity of th ese atomic features is consistent with the velocity of the center of m ass of this known spectroscopic binary. For the CO bands, we obtained a best fit from a four-component model, consistent for all three bands . There are three emission components and one absorption component. Tw o emission components display narrow velocity spreads (29 km s(-1)), a nd one shows a rotational temperature of 50 K, the other, of about 300 0 K. The third emission component has a very wide velocity spread (600 km s(-1)) and a rotational temperature of about 100 K. The absorption component shows a wide velocity spread (230 km s(-1)) and a rotationa l temperature of about 100 K. The high-temperature emission displayed partially-resolved rotational line structure corresponding to levels o f J = 50. The Doppler shifts of these features place the narrow, cold emission with one of the binary components and the narrow, hot emissio n with the center of mass. 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 young stellar objects.