Central Bureau for Astronomical Telegrams
IAUC 6459: P/1996 N2; GRS 1915+105
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Circular No. 6459
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 P/1996 N2 (ELST-PIZARRO)
P. Pravec, Ondrejov Observatory, writes: "Measurements of my
CCD images of P/1996 N2 taken with the 0.65-m telescope on Aug.
21.973-21.977 UT reveal the presence of a stellar nucleus and a
straight, narrow tail 3'.5 long extending from the nucleus along a
line in p.a. 251.4 +/- 0.4 deg with dispersion of a few arcsec.
This is only 1 deg less than the p.a. of the line of variation of T
for the orbit published on IAUC 6457, but it is nearly opposite the
antisolar direction. If the tail is composed of material spread
along the orbit, the material is distributed within an interval of
Delta(T) from 0.00 to +0.15 day with respect to the object's
position. However, the projection of a relatively normal dust tail
could cause a similar phenomenon, if the tail deviates from the
prolonged radius vector, because the earth is very close to the
object's orbital plane."
Z. Sekanina, Jet Propulsion Laboratory, reports: "The comet's
narrow, straight, structureless tail is likely to be a signature of
a past dust-emission episode. Even though the very low inclination
strongly degrades the accuracy with which the event's timing can be
determined, the 1-sigma error of the tail's position angle reported
by Pravec (above) suggests that the presumed outburst probably
occurred between late May and early July 1996, or some 40 to 80
days after perihelion, in which case the maximum effect of solar
radiation pressure on dust in the tail was between 0.05 and
about 0.4 the solar attraction (implying the presence of micron- or
submicron-sized grains). Information from the Elst tail-length
estimate in mid-July and from Offutt's observation on Aug. 21
(IAUC 6456) leads to similar constraints. In an effort to improve
the time determination of the presumed outburst, it is desirable to
measure the tail's position angle with maximum possible accuracy.
It is also recommended that a search be initiated for possible
prediscovery observations from the critical interval to ascertain
the object's physical appearance at the time."
GRS 1915+105
S. Sazonov and R. Sunyaev, Space Research Institute, Moscow,
on behalf of the GRANAT/WATCH team, report x-ray observations on
June 7, simultaneous with those reported on IAUC 6455, when GRS
1915+105 was in a high flaring state, with a flux of approximately
0.4 Crab in the range 8-20 keV.
(C) Copyright 1996 CBAT
1996 August 22 (6459) Daniel W. E. Green
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