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IAUC 6335: C/1996 B2; GRO J1744-28

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IAUC number

                                                  Circular No. 6335
Central Bureau for Astronomical Telegrams
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)
Phone 617-495-7244/7440/7444 (for emergency use only)

     M. Senay, University of Hawaii (UH); H. Matthews, Joint
Astronomy Centre, Hilo, and Herzberg Institute of Astrophysics,
Ottawa; and D. Jewitt, UH, write:  "We report the detection of CO
(3-2) emission from C/1996 B2 at the James Clerk Maxwell Telescope
on Mauna Kea on Mar. 1.54 and 2.52 UT.  Observations on Mar. 1.54
showed the line at -57.96 +/- 0.03 km/s, with peak antenna
temperature 0.32 K, area 0.37 +/- 0.02 K km/s, width 1.08 +/- 0.07
km/s, and an ephemeris geocentric radial velocity -57.94 km/s.  All
quantities were confirmed on Mar. 2.52.  Assuming rotational
temperatures of 30 and 50 K, we estimate log Q(CO) = 28.00 and
28.04, respectively.  This compares with log Q(OH) = 28.73 on Mar.
1.5 (IAUC 6333).  The implied Q(CO)/Q(OH) = 0.2 is similar to
CO/H2O = 0.15 derived for 1P/Halley (Woods et al. 1986, Nature 324,
436).  Available evidence thus points to a comet that is like
1P/Halley both in its absolute gas production and in its CO/OH and
HCN/OH (IAUC 6318) ratios.  Sample spectra may be examined at

GRO J1744-28
     B. A. Harmon, Marshall Space Flight Center, NASA; J. van
Paradijs and W. S. Paciesas, University of Alabama, Huntsville; and
S. N. Zhang and C. Kouveliotou, Universities Space Research
Association, report for the BATSE Team:  "The 20- to 100-keV flux
of GRO J1744-28, as measured with BATSE using earth occultations,
has steadily decreased from 0.9 photon cmE-2 sE-1 on Feb. 19 to 0.5
photon cmE-2 sE-1 on Mar. 2.  This may signal the upcoming end of
the outburst of this unique source.  No convincing optical/infrared
counterpart of the source has so far been found, likely due to its
high interstellar extinction (Augusteijn et al., IAUC 6326).  The
non-detection of a V-band counterpart implies that the interstellar
column density, NH, is at least 2 x 10E22 cmE-2.  At a source
distance of 7 kpc, the unabsorbed apparent K magnitude is expected
to be about 13.  Since the K-band extinction, A(K), increases with
column density by A(K)/NH about 7.5 x 10E-23 mag cm**2, the only way
to identify a counterpart would appear to be deep K-band imaging
centered on the variable radio source (IAUC 6323) down to at least
mag 19.  In view of the possible upcoming termination of the
outburst, we urge observers that such images be made as soon as

                      (C) Copyright 1996 CBAT
1996 March 5                   (6335)            Daniel W. E. Green

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