Central Bureau for Astronomical Telegrams
IAUC 6223: C/1995 O1; GRO J1735-27
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Circular No. 6223
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/1995 O1 (HALE-BOPP)
Z. Sekanina, Jet Propulsion Laboratory, writes regarding the
items on IAUC 6216 and 6220: "The fact that the jet did not move
much in 24 hr, combined with the meager effect of radiation
pressure, implies that particle velocities must be very small (much
less than 100 m/s). Since the curvature of the jet cannot be due
to radiation pressure, it must be due to the spatial distribution
of particle velocity vectors --- i.e., the particles must have
been ejected from an area far from the pole. Furthermore, the
jet's foreshortening orientation suggests that the projected
direction of the spin axis was probably along the line near p.a.
100-280 deg; the earth could not be too close to the equatorial
plane, or we should see the spiral projected nearly edge-on. If
one assumes that the 'tip' of the jet near p.a. 290 deg was the
beginning of the emission episode and its 'top' (slightly east of
north) was its end, occurring at local sunset, one gets a compact
set of solutions for the spin-axis position (R.A. about 45 deg,
Decl. about +10 deg, obliquity 140-150 deg). In any event, the
emission began about when the source transited the subsolar
meridian. The rotation period is entirely indeterminate, except
that it could not be greater than about 10 days, but the emission
episode must have lasted very nearly 1/4 of the rotation period.
Assuming a particle velocity of 10 m/s (unforeshortened) on the
near side of the jet (relative to the nucleus), the age of the jet
(on Aug. 31) might be about 35 days. The available images suggest
that this emission episode was not the only one, a conclusion that
is consistent with the spiral reported in late July (IAUC 6194).
One can infer that C/1995 O1 might be (relatively) CO-rich and, at
the same time, dust-rich. If such CO supplies would last until
perihelion, then the comet could indeed become very bright. Yet,
it does not have to have an excessively large nucleus."
GRO J1735-27
A. J. Castro-Tirado, Laboratorio de Astrofisica Espacial y
Fisica Fundamental, Madrid, reports: "We examined the error box of
the x-ray transient source GRO J1735-27 (IAUC 6207, 6222) on a
Schmidt plate taken by K. Birkle at the German-Spanish Calar Alto
Observatory on Aug. 25; nothing obvious down to B about 17 is seen.
We also expanded our search to the error box of the Ginga source GS
1734-275 (IAUC 4571, 6212), slightly outside of the BATSE error
box; that result was negative as well. Further soft-x-ray
observations are encouraged to confirm whether GRO J1735-27 is
related to the x-ray transient observed by ROSAT (RX J1735.9-2726,
IAUC 6212) and Mir-Kvant/TTM (KS 1732-273, IAUC 6216)."
1995 September 8 (6223) Daniel W. E. Green
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