[ITAL]Far Ultraviolet Spectroscopic Explorer[/ITAL] Observations of CO and H[TINF]2[/TINF] Emission in Comet C/2001 A2 (LINEAR)

Abstract

Observations of comet C/2001 A2 (LINEAR) were made with the Far Ultraviolet Spectroscopic Explorer beginning 2001 July 12.58 and coinciding with a photometric increase of ∼1.5 mag. Spectra were obtained in the 905-1180 A ˚ range at 0.25 A ˚ spectral resolution using the aperture. Several new cometary emissions 30 # 30 were identified, particularly the bands of the CO Hopfield-Birge systems C-X and at 1088 and 1151 A ˚ , (0, 0) B-X respectively, O i (1 D-1 D) at 1152 A ˚ , and three lines of the H 2 Lyman system at 1071.6, 1118.6, and 1166.8 A ˚ , pumped by solar Lyb fluorescence. Also detected were O i multiplets at 989, 1027, and 1040 A ˚ and several lines of the H i Lyman series. The rotational envelopes of the CO bands are resolved and appear to consist of both "cold" and "hot" components, the cold component accounting for 70% of the flux and with a rotational temperature of K. The hot component may be indicative of a CO 2 source. The CO bands, H 2 lines, and O i l1152 all 55 5 decreased by a factor of 2 over the 7.5 hr observation. The derived time-averaged production rates are Q(CO) p molecules s and molecules s. These values may be uncertain by as much 27 1 2 9 1