Central Bureau for Astronomical Telegrams
IAUC 6495: C/1996 Q1; P/1996 N2
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Circular No. 6495
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
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)
BMARSDEN@CFA.HARVARD.EDU or DGREEN@CFA.HARVARD.EDU (science)
Phone 617-495-7244/7440/7444 (for emergency use only)
COMET C/1996 Q1 (TABUR)
K. Dennerl, J. Englhauser, and J. Truemper, Max-Planck-
Institut fuer Extraterrestrische Physik, Garching; and C. Lisse,
Goddard Space Flight Center, NASA, communicate: "X-ray emission
from comet C/1996 Q1 was detected with the ROSAT High Resolution
Imager. The observations were performed on several occasions
between Sept. 26 and Oct. 6, when Delta = 0.51-0.42 AU and r =
1.09-0.99 AU. The x-ray emission was highly variable on time
scales of hours (or less), both in intensity (at least by a factor
of five) and morphology, with episodes of considerable deviation
from the crescent shape of C/1996 B2 (Hyakutake) observed under
similar phase angles (IAUC 6373). The brightest parts of the
emission were always concentrated in an area with a typical extent
of 5' (90 000 km) and displaced sunward from the nucleus by about
100" (30 000 km). They reached a peak surface brightness of 0.01
count sE-1 arcminE-2, similar to that of comet C/1996 B2 during its
close approach to the earth in Mar. The rapid morphological
changes seem to rule out any scattering of solar x-rays by material
in the comet's coma as the dominant mechanism for producing the
bright parts of the x-ray emission."
COMET P/1996 N2 (ELST-PIZARRO)
H. Boehnhardt, University of Munich, reports on behalf of the
European Southern Observatory (ESO) Rosetta/ISO Target Comets
Imaging Team: "Images of the comet were taken by R. Schulz (Max-
Planck-Institut fuer Aeronomie, Katlenburg-Lindau), G. P. Tozzi
(Arcetri Observatory), and H. Rauer (Meudon Observatory) on Sept.
16 and Oct. 4 with, respectively, the 2.2-m MPG/ESO telescope (+
EFOSC2) and the Danish 1.54-m telescope (+ DFOSC) at La Silla.
These images show a long antitail in p.a. 254-255 deg and a
previously undetected antisolar tail in p.a. 69 deg (as predicted
on IAUC 6473). Preliminary analysis by Z. Sekanina and myself
indicates that dust was being released from the object over a
period of many weeks or months until approximately mid-July 1996,
when the comet was discovered (IAUC 6456). This evidence
eliminates the possibility that the features are products of an
instant event (e.g., a collision). Dust particles subjected to
solar-radiation-pressure accelerations of up to 0.05 the solar
attraction are clearly apparent in the antisolar tail."
(C) Copyright 1996 CBAT
1996 October 19 (6495) Daniel W. E. Green
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