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Circular No. 6370 Central Bureau for Astronomical Telegrams INTERNATIONAL ASTRONOMICAL UNION Postal Address: Central Bureau for Astronomical Telegrams Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A. IAUSUBS@CFA.HARVARD.EDU or FAX 617-495-7231 (subscriptions) BMARSDEN@CFA.HARVARD.EDU or DGREEN@CFA.HARVARD.EDU (science) Phone 617-495-7244/7440/7444 (for emergency use only) COMET C/1996 B2 (HYAKUTAKE) P. D. Feldman, Johns Hopkins University; M. Festou, Observatoire de Midi-Pyrenees, for the IUE ToO Team for Comet Observations; and P. M. Rodriguez and R. Gonzalez, European Space Agency IUE Observatory, report: "Further observations (IAUC 6355) were made in both the SWP and LWP range on Mar. 27.6 and 27.7 UT with the International Ultraviolet Explorer (IUE) on the nuclear region of comet C/1996 B2. The observations clearly show the presence of the strongest CO Cameron bands at 199.3, 206.3, and 215.8 nm, as well as the CO+ first negative bands at 211.4 and 219.1 nm. At this time, the water-production rate was derived as 2.4 x 10E29 sE-1, which is close to the level seen on Mar. 23.12, and significantly less than observed on Mar. 25.06, suggesting that the nucleus lost some small pieces. The Cameron bands are produced primarily by the photodissociation of CO2 and a preliminary estimate of Q(CO2) is 2.5 x 10E28 sE-1. The CO-production rate is found to be 7 x 10E27 sE-1, derived from the observed optically- thin fourth positive bands at 154.5 and 159.7 nm. This is considerably lower than the CO-production rate derived from sub- millimeter observations earlier in the month (IAUC 6353), and suggests that most of the CO in the coma is derived from a distributed source, as was the case for 1P/Halley." Visual m1 estimates, made in strong moonlight: Apr. 1.21 UT, 2.1 (C. E. Spratt, Victoria, BC, naked-eye); 1.84, 1.8 (M. L. Paradowski, Lublin, Poland, 7x35 binoculars); 2.06, 2.0 (G. W. Kronk, Troy, IL, naked eye). COMET 29P/SCHWASSMANN-WACHMANN 1 I. Ferrin, Universidad de los Andes, Merida, reports that CCD images of comet 29P were taken in V, R, and I on Mar. 24.35 UT with the 1-m Schmidt telescope of the National Observatory of Venezuela, showing a coma diameter of 216" and an intense jet between p.a. 238 and 288 deg (maximum intensity at p.a. 269 deg; solar direction 281 deg). There is also the remains of a second jet at p.a. 338 deg. Preliminary photometry of the whole coma gives V = 12.9 +/- 0.15. Further total visual magnitude estimates (cf. IAUC 6351): Mar. 24.05 UT, 11.1 (J. Carvajal, Teruel, Spain, 0.44-m reflector); 27.88, 10.9 (K. Hornoch, Lelekovice, Czech Republic, 0.35-m reflector). (C) Copyright 1996 CBAT 1996 April 2 (6370) Daniel W. E. Green
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