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IAUC 6555: C/1995 O1

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                                                 Circular No. 6555
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Mailstop 18, 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)
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COMET C/1995 O1 (HALE-BOPP)
     E. Kreysa, W. Altenhoff, and C. G. T. Haslam, Max-Planck-
Institut fur Radioastronomie, Bonn; and A. Sievers, Institut de
Radio Astronomie Millimetrique (IRAM), Granada, report the
detection of comet C/1995 O1 in the continuum at 250 GHz with the
IRAM 30-m radio telescope on Pico Veleta.  The preliminary results
(with internal/absolute errors) are:  Feb. 1.355 UT, 102 +/- 6/15.3
mJy; 2.345, 92 +/- 2/13.8 mJy.  Multiple scans through the comet
give no indication for a significant beam broadening.  Under the
assumption of a nuclear diameter of order 30 km, more than 90
percent of the observed signal must come from the (ice) particle
halo."
     C. W. Hergenrother and S. M. Larson, Lunar and Planetary
Laboratory; and B. G. Marsden, Center for Astrophysics, report the
appearance of changing structure in jets of C/1995 O1 from
processed R-band CCD images obtained with the 1.2-m Whipple
Observatory telescope on Feb. 1.5 UT.  Confirming CCD observations
were obtained by R. Tucker (Goodricke-Pigott Observatory) with a
0.36-m telescope on Feb. 1.5 and 3.5.  Bright linear jets are seen
at p.a. 25, 166, and 208 deg and fainter ones at 91 and 306 deg.
An additional bright but curved jet is seen close to and south of
the central condensation on both days with different orientations
-- though apparently related to the two southern jets, which
contain at least five periodic brightness enhancements 8" apart
extending along each jet.  Each enhancement in both of these jets
has curved tail-like extensions fading towards the approximate
anti-solar direction.  Further observations providing better
temporal coverage are encouraged to see if the production mechanism
is rotationally modulated, or if some other process is responsible.
     H. Mikuz, Crni Vrh Observatory, reports the following total
integrated magnitudes from V-filtered CCD images taken through
camera lenses of focal lengths 180 (f/2.8) and 90 mm (f/4):  Jan.
16.22 UT, 2.8 (180); 17.20, 2.8 (180); 29.20, 2.2 (90); 31.21, 2.3
(90); Feb. 3.20, 2.0 (90, 180); 4.21, 1.9 (90, 180).  The coma
diameters were about 50' in the 180-mm lens and about 60' in the
90-mm lens.  Further naked-eye m1 estimates:  Jan. 9.53 UT, 3.1 (A.
Hale, Cloudcroft, NM); 13.21, 2.8 (R. Haver, Frasso Sabino, Italy);
17.45, 2.7 (J. E. Bortle, Stormville, NY); 21.50, 2.5 (G. W. Kronk,
Troy, IL); 26.21, 2.4 (M. Plsek, Lelekovice, Czech Rep.); 27.23,
2.5 (R. J. Bouma, Groningen, The Netherlands); 31.24, 2.3 (B. H.
Granslo, Fjellhamar, Norway); Feb. 2.17, 2.0 (K. Sarneczky,
Budapest, Hungary; 7 deg tail in p.a. 330 deg); 3.21, 1.9 (V.
Znojil, Brno, Czech Rep.); 4.14, 1.8 (A. Baransky, Kiev, Ukraine).

                      (C) Copyright 1997 CBAT
1997 February 5                (6555)            Daniel W. E. Green

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