Circular No. 6645
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Mailstop 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
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COMET C/1995 O1 (HALE-BOPP)
     P. Colom, Observatoire de Paris (OP); D. Despois, Observatoire
de Bordeaux; B. Germain, OP; R. Moreno and G. Paubert, Institut de
Radioastronomie Millimetrique (IRAM); N. Biver, D. Bockelee-Morvan,
J. Crovisier, E. Gerard, E. Lellouch, and H. Rauer, OP; J. K.
Davies, Joint Astronomy Centre, Hilo; and W. R. F. Dent, Royal
Observatory, Edinburgh, report:  "On Apr. 5 UT, we detected the
blend of J(21-20) lines of CH_3OCHO (methyl formate) in C/1995 O1
at 227.562 GHz with the IRAM 30-m telescope.  The total integrated
line area in the main-beam brightness temperature scale is 0.22 +/-
0.03 K km sE-1.  A preliminary estimate of the CH_3OCHO production
rate is 6 x 10E27 molecules/s, which corresponds to an abundance
relative to CH_3OH of about 3 percent."
     R. W. Russell, D. K. Lynch, and A. L. Mazuk, The Aerospace
Corporation, report the clear detection of features at 11.8 and
11.25 microns in the high signal-to-noise BASS spectra of comet
C/1995 O1 in 1996 October and November, similar to features seen in
the spectra of comet 1P/Halley.  Spectral-synthesis modeling
results in the identification of both features with emission by
crystalline olivine grains, adding strength to their earlier
detection (Bregman et al. 1987, A.Ap. 187, 616) and identification
with crystalline olivine (Campins and Ryan 1989, Ap.J. 341, 1059)
in 1P/Halley.  In contrast to the earlier work, this model uses
laboratory emissivity data on celestial dust-analogue samples as
inputs.  The presence of all of the expected structure in the
region 8-13 microns strengthens the identification with a
crystalline component of olivine-like composition in this comet.


GS 1843+00
     K. Dennerl, Max-Planck-Institut fur Extraterrestrische Physik,
Garching; and J. Greiner, Astrophysical Institute, Potsdam, write:
"This x-ray binary pulsar was very likely observed with the ROSAT
High Resolution Imager (HRI) on Apr. 4.6608-4.6662 UT, when it had
already declined back to the BATSE detectability threshold.  A
source was found at R.A. = 18h45m36s.9, Decl. = +0o51'45" (equinox
2000.0; 90-percent confidence error radius 10"), with an average
countrate of 0.05 +/- 0.01 HRI count/s.  This source -- the only
object detected in this observation -- is within the 2' error
radius of RXTE (cf. IAUC 6605).  It was not present during an HRI
observation on 1994 Apr. 8.5596-8.6348, which yields a 3-sigma
upper limit of 8 x 10E-4 HRI count/s.  A direct identification with
GS 1843+00 by detecting the 29.6-s pulsations is impossible due to
limited photon statistics."

                      (C) Copyright 1997 CBAT
1997 May 7                     (6645)            Daniel W. E. Green