Infrared Spectroscopy of U Equulei’s Warm Circumstellar Gas

Medium and high resolution spectroscopy of U Equulei from 1 to 4 micronsduring 1997-2003 has revealed information about its unusual circumstellarenvelope, observed previously at optical and radio wavelengths. Strongabsorption bands of H2O and of CO dominate the 1-4um spectrum. The gas has amean temperature of 600 K and 12C/13C =< 10. The CO 2-0 line profiles andvelocities imply no net ejection or infall and indicate either rapid radial gasmotions being seen along a narrow continuum beam, or absorption by orbiting gasthat is nearly coincident with a highly extended continuum source. The gascould be located in a disk-like structure. The observed high column densitiesof warm CO and H2 normally would be associated with sufficient dust tocompletely obscure the star at optical wavelengths. The observations thusindicate either a highly abnormal gas-to-dust ratio, consistent with theearlier optical observation of abundant refractory metal oxides in thecircumstellar gas, or peculiar geometry and/or illumination.Comment: 21 pages incl. 8 postscript figures and 1 table; typos correcte