IUE Observations of Comets P/Brorsen-Metcalf and Okazaki-Levy-Rudenko

Comet P/Brorsen-Metcalf (1989o) was observed with the International Ultraviolet Explorer (IUE) on several dates from 27 July 1989 through 5 August 1989; comet Okazaki-Levy-Rudenko (1989r) was observed in low dispersion with IUE on 2 and 22 December 1989. The water production rates for P/Brorsen-Metcalf derived from OH measurements using the vectorial model of Festou (1981) were 4.2, 4.6, 5.3, 4.9, 6.2, and 6.7 x 1028 on 27.2 and 31.1 July, 1.8, 2.4, 3.9, and 5.2 August 1989, respectively. These are plotted in Fig: 1. For perspective, water production rates estimated from postperihelion visual magnitudes using the method of Newburn (1981; see also Roettger et al., 1990) are also plotted. Fig. 2 shows the water production rates (squares) for comet Okazaki- Levy- Rudenko, which were 5.3 and 4.0 x 1028 on 21.9 and 22.2 December 1989. The 21 December measurement has a greater uncertainty, as it was derived from the OH (1,1) band, in a noisier region of the IUE camera. Results using a newer version code for the vectorial model are also plotted, (diamonds); they are within a few percent of the previous results. The numbers listed are from the older code, to maintain consistency with published results for other comets. Also plotted in Fig. 2 are two estimates of the water production rate from the OI emission around 1304 Å (octagons),. The higher point is from a Haser model, and should be an overestimation as oxygen is primarily a granddaughter product. The lower point was obtained by analogy with observations of comet Bradfield 1979X, a comet with similar IUE spectra and geometric parameters. These should be considered rough estimates only.