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IAUC 6162: Poss. Sats OF SATURN; AL Com

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                                                  Circular No. 6162
Central Bureau for Astronomical Telegrams
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)
Phone 617-495-7244/7440/7444     TWX 710-320-6842 ASTROGRAM CAM

     M. K. Gordon, C. D. Murray and K. Beurle, Queen Mary and
Westfield College, University of London, report on the possible
existence of additional satellites of Saturn in the Voyager 2 data.
They also quote S. P. Synnott as noting that the seven satellite
candidates discussed by him on IAUC 3651, 3656, and 3660 should be
reduced to three (S/1981 S 7, 10, and 11), together with a very
faint fourth one, designated S/1981 S 14, observed on 1981 Aug.
23.9955 UT around 2.0 x 10**5 km from Saturn.  Summarized below are
the 1981 Aug. UT dates of the new images (not the 'earth received'
times), approximate planet-centered distances (in units of 10**5 km)
and longitudes (in deg), assuming circular orbits in the equatorial
plane (in J2000.0 coordinates fixed on 1981 Aug. 21.2), and
estimated apparent visual geocentric opposition magnitudes:  S/1981
S 15, 21.2439, 1.74, 222, 18; S/1981 S 16, 21.2789, 2.20, 290, 18;
S/1981 S 17, 22.1928, 2.31, 282, 18; S/1981 S 18, 23.9050, 1.85,
206, 24; S/1981 S 19, 23.9866, 1.86, 109, 22.  Pointing-error
corrections in the Voyager database for S/1981 S 18 and 19 could
not be corrected; consequently, the error bars for these two
features are on the order of two to three thousand km.  The orbital
radii above are particularly sensitive to the assumption that the
possible satellites are on orbits in the equatorial plane.  Orbits
with moderate inclinations (1-1.5 deg) could produce changes of
several thousands of kilometers in the radial positions.  Based on
dynamical considerations, S/1981 S 16 and 18 may be separate
observations of a single small satellite coorbital with Mimas
(Saturn I) with an orbital inclination comparable to that of Mimas.

     W. Pych and A. Olech, Warsaw University Observatory, write:
"Time-series observations of AL Com were collected with the 0.60-m
telescope (+ Tek512 CCD camera) on three nights (Apr. 10.026-10.104,
10.805-10.896, and 11.783-11.994 UT) at the Ostrowik Observatory of
Warsaw University.  Observations were made in the Cousins I (first
night) and V bands.  We confirm the presence of coherent periodic
light variations (cf. IAUC 6157).  The best period for our entire
data set is 81.5 +/- 0.2 min.  Also, the first harmonic period
(40.8 min) is clearly detectable.  The peak-to-peak amplitude in
the V and I bands was about 0.05 and 0.06 mag, respectively."

1995 April 14                  (6162)            Daniel W. E. Green

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