Central Bureau for Astronomical Telegrams
IAUC 6575: C/1995 O1
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Circular No. 6575
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/1995 O1 (HALE-BOPP)
J. M. Veal and L. E. Snyder, University of Illinois; M. C. H.
Wright, J. R. Forster, W. Hoffman, M. Pound, I. de Pater, T.
Helfer, R. L. Plambeck, G. Engargiola, and T. Wong, University of
California at Berkeley; L. M. Woodney and M. F. A'Hearn, University
of Maryland; P. Palmer, University of Chicago; and Y.-J. Kuan,
Institute of Astronomy and Astrophysics, Academia Sinica, Taiwan,
report the detection of HCO+ from comet C/1995 O1 using seven
antennae of the Berkeley-Illinois-Maryland-Association Array in
autocorrelation mode: "The J=1-0 transition at rest frequency
89.189 GHz was detected in emission on Feb. 19, 22, and 28 UT with
peak antenna temperatures (Ta*) of 80, 80, and 100 mK, respectively.
The HCO+ spectral lines are consistently asymmetric with a redward
wing. The full widths at half maximum (not including the redward
wing) are equal to 3.0 +/- 0.2, 4.5 +/- 0.2, and 3.0 +/- 0.2 km/s,
with line centers (also not including the redward wing) at +1.6 +/-
0.2, +1.8 +/- 0.2, and +1.1 +/- 0.2 km/s with respect to the comet
nucleus, respectively. Relative to the main emission component,
the redward wing is about 1/3 the peak temperature and is displaced
by about +3.7 km/s from the line center. We believe this to be the
first detection of HCO+ in a comet."
T. Kawabata and K. Ayani, Bisei Astronomical Observatory (BAO),
report observations with K. Kinoshita and M. Fujii at the BAO 1-m
telescope: "High-resolution (instrumental FWHM = 0.06 nm) slit
spectra of C/1995 O1 show emission lines of Na D1 and D2 on Feb.
26.9 UT; the observed velocities within 7" of the comet's nucleus
in the north-south slit were -32 and -29 km/s for D1 and D2,
respectively, while nearby absorption lines have an average
velocity of -48 +/- 3 km/s. It appears that the Na emission has an
asymmetric spatial profile and is more extended toward the south
(dust-tail side) than the north."
F. Mannucci, CAISMI, CNR, Florence; and G.-P. Tozzi,
Osservatorio Astrofisico di Arcetri, write: "Near-infrared J, H,
and K observations with the TIRGO telescope between Feb. 3 and 10
show several shells with a projected velocity of 0".80/hr,
confirming a rotation period of about 12 hr (cf. IAUC 6560).
Preliminary analysis shows that the nucleus' spin-axis position is
almost perpendicular to the line-of-sight with p.a. about 40 deg;
the latitude of the active spot (about -65 deg) is more uncertain.
The jet velocity appears to be on the order of 0.35-0.45 km/s."
(C) Copyright 1997 CBAT
1997 March 4 (6575) Daniel W. E. Green
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