Central Bureau for Astronomical Telegrams
IAUC 7051: Sats, RINGS OF NEPTUNE; P/1998 U3
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Circular No. 7051
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)
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Phone 617-495-7244/7440/7444 (for emergency use only)
SATELLITES AND RINGS OF NEPTUNE
C. Roddier, F. Roddier, J. E. Graves, O. Guyon, and M. J.
Northcott, Institute for Astronomy, University of Hawaii (UH); and
B. Sicardy, Paris-Meudon Observatory, report: "Infrared (1.72-
micron) images of Neptune taken on July 6 with the UH adaptive
optics system (Hokupa'a) mounted on the Canada-France-Hawaii 3.6-m
telescope have now been thoroughly processed. In addition to the
observations of Neptune VI (Galatea), VII (Larissa), and VIII
(Proteus) reported on IAUC 6987, Neptune V (Despina) and Neptune's
ring arcs have also been detected. Despina, which was far from
maximum elongation, moved substantially during the 600-s exposure
time, but its average position is consistent within +/- 1 deg of
that estimated from Voyager 2 data in 1989 (as for Proteus and
Larissa). Each of the three brightest arcs Liberte, Egalite, and
Fraternite are identified. The fainter leading arc Courage cannot
be confirmed. The positions of the main arcs are close to that
given by the second orbital solution of Nicholson et al. (1995,
Icarus 113, 295), which corresponds to a mean motion of 820.1118
deg/day. Photometric profiles of the arcs have been obtained and
compared with those of Porco (1991, Science 253, 995), allowing
for the blur due to our 600-s integration time. For the two
trailing arcs (Fraternite and Egalite), the fit is very good. It
shows that the arcs are 4 +/- 2 deg ahead of the position estimated
from Nicholson's second solution. For Liberte the uncertainty is
larger due to noise. Four 200-s exposures made in the J band were
also analyzed. The arcs were not detected. However, the data
confirm that Galatea is 5 +/- 1 deg ahead of the nominal predicted
position (IAUC 6987). In these data, Despina is closer to maximum
elongation. Its image is sharper and its position is again
consistent within +/- 1 deg with that predicted from Voyager data.
We note that the uncertainties in the orbital parameters derived
from Voyager data by Owen et al. (1991, A.J. 101, 1511) lead to the
following standard errors on the current satellite longitudes: +/-
2.9 deg for Proteus, +/- 5.2 deg for Larissa, +/- 9.1 deg for
Despina, and +/- 8.1 deg for Galatea. The estimated errors are
believed to be conservative by typically a factor of two (ibid.).
Further analysis is thus required to see if the Galatea O-C is
significant or a mere effect of the accumulation of error between
1989 and 1998."
COMET P/1998 U3 (JAGER)
Visual m_1 estimates by K. Hornoch, Lelekovice, Czech Republic
(0.35-m reflector): Oct. 30.84 UT, 12.0; Nov. 11.80, 11.2; 12.82,
11.3.
(C) Copyright 1998 CBAT
1998 November 14 (7051) Daniel W. E. Green
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