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IAUC 6561: C/1997 BA6

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                                                  Circular No. 6561
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)
URL http://cfa-www.harvard.edu/cfa/ps/cbat.html
Phone 617-495-7244/7440/7444 (for emergency use only)


COMET C/1997 BA6 (SPACEWATCH)
     MPEC 1997-C05 and 1997-C13 give observations of what appeared (using
telescopes of aperture up to 1.2 m) to be an asteroidal object discovered by
the Spacewatch program on Jan. 31 (with also prediscovery images on Jan. 11).
The object, designated 1997 BA6, was distant and intrinsically bright
(r = 9.0 AU, H = 10.0).

     J. W. Parker and H. F. Levison, Southwest Research Institute;
and R. Fesen, Dartmouth College, report that 21 two-minute exposures with
the M.I.T.-Dartmouth-Michigan 2.4-m Hiltner Telescope at Kitt Peak on
Feb. 10 show 1997 BA6 clearly to have a coma.  All the images were centroided,
shifted and summed to produce an equivalent 42-min exposure wherein the
object was stationary.  The FWHM's of comparison stars (similarly
centroided, shifted and summed) were all consistently 1".2, while the
FWHM of 1997 BA6 was 1".7.

     K. Meech, O. Hainaut and J. Bauer, University of Hawaii, report:
"CCD images of 1997 BA6, obtained with the University of Hawaii 2.2-m
telescope on Mauna Kea on Feb. 17 and 18 UT, show a low-surface-brightness
coma surrounding the object.  The images were taken through the
Kron-Cousins R filter, and the coma was visible in a 1200-s integration on
the first night, while a deeper image (4800 s) was obtained on Feb. 18 in
conditions of moderate seeing (0".9).  The asymmetric coma extends
to a distance of 3".7 (2.1 x 10**4 km) in p.a. 7 deg.  The brightness
falls off very rapidly from the core--by steeper than rho**-2}, rho being
the projected distance from the image center."

     The following orbital elements are taken from MPC 29067:

                    Epoch = 1999 Dec.  8.0 TT
     T = 1999 Dec.  4.3655 TT         Peri. = 286.1624
     e = 0.987450                     Node  = 317.6522  2000.0
     q = 3.447727 AU                  Incl. =  72.4459

1997 TT     R. A. (2000) Decl.     Delta      r    Elong. Phase      m2
Feb. 21     9 13.28    +12 58.5    7.929    8.885  164.1    1.8     19.5
Mar.  3     9 08.63    +12 58.8    7.926    8.821  153.0    2.9     19.5
     13     9 04.40    +12 57.7    7.953    8.758  142.1    4.0     19.6
     23     9 00.73    +12 54.8    8.004    8.695  131.3    4.9     19.6
Apr.  2     8 57.75    +12 49.6    8.077    8.631  120.8    5.7     19.7
     12     8 55.54    +12 41.9    8.165    8.568  110.5    6.3     19.7
     22     8 54.14    +12 31.5    8.264    8.504  100.4    6.7     19.7

                      (C) Copyright 1997 CBAT
1997 February 19               (6561)              Brian G. Marsden

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