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IAUC 6587: C/1995 O1

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                                                 Circular No. 6587
Central Bureau for Astronomical Telegrams
Mailstop 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
IAUSUBS@CFA.HARVARD.EDU or FAX 617-495-7231 (subscriptions)
URL http://cfa-www.harvard.edu/cfa/ps/cbat.html
Phone 617-495-7244/7440/7444 (for emergency use only)

     R. West, European Southern Observatory; and M. Kidger,
Instituto de Astrofisica de Canarias, report on behalf of the
European Comet Hale-Bopp Team:  "High-resolution observations taken
with the 1-m Jacobus Kapteyn Telescope of the Observatorio del
Roque de los Muchachos by J. Licandro (Instituto de Astrofisica de
Canarias) and P. Rudd (Royal Greenwich Observatory) on Mar. 6.2 UT
broadly confirm the observations of Birkle and Boehnhardt reported
on IAUC 6583.  Observations were taken through a CN and a blue
continuum filter, with Laplacian filtering applied to the reduced
images.  The images reveal both spiral-jet and arc structures.  The
spiral jet is seen in both filters and leaves the nucleus at p.a.
about 200 deg, turning through a right angle at about 3" from the
nucleus and continuing in p.a. 110 deg.  A bright shell is also
seen in both filters 20" to the southwest of the nucleus, which
corresponds to a recently separated jet.  Two diffuse arc
structures are also seen to the north and east of the nucleus.  The
northern arc is only seen in the CN images, centered at 18" from
the nucleus, and it extends from p.a. 90 deg to 270 deg through the
north, being clearly elliptical, with the major axis in p.a. 340
deg.  A second and fainter arc can be seen only in the continuum-
subtracted CN image and extends from p.a. 30 deg to 120 deg,
centered about 27" from the nucleus.  The CN and continuum images
can be found at http://www.iac.es/comet/ima97/mar5ifin.jpg.
Assuming, as on IAUC 6583, that the two arcs are ejected by the
same active spot and that the nucleus rotates with an 11.47-hr
period (Lecacheaux et al., IAUC 6560; Jorda et al., IAUC 6583), we
obtain an expansion velocity for CN of 1.3 km/s for a 60-deg
rotation between arc emissions, very close to the velocity
calculated by Birkle and Boehnhardt."
     J. E. Wink, Institut de Radio Astronomie Millimetrique (IRAM),
Grenoble, reports on behalf of the continuum and molecular-lines
observing teams (headed by W. J. Altenhoff, Max Planck Institut fur
Radioastronomie; and D. Bockelee-Morvan, Observatoire de Paris,
respectively):  "We have detected the millimeter-wave continuum of
C/1995 O1 with the IRAM Plateau de Bure Interferometer at 3 mm
(resolution 3".5) and at 1 mm (resolution 1".5) on Mar. 9 and 11.
On Mar. 11.4 UT, the flux density of the unresolved nucleus was 24
+/- 1 mJy at 229 GHz.  This flux can be accounted for by thermal
radiation at blackbody temperature 380 K from a 1600-km**2 area,
which corresponds to a sphere of diameter 45 km.  These
observations were made simultaneously with molecular-line
observations, which detected cometary emissions centered at the
continuum position."

                      (C) Copyright 1997 CBAT
1997 March 14                  (6587)            Daniel W. E. Green

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