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IAUC 8836: S/2007 S 1, S/2007 S 2,, S/2007 S 3; (4951); P/2007 C2

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IAUC number

                                                  Circular No. 8836
Central Bureau for Astronomical Telegrams
Mailstop 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
IAUSUBS@CFA.HARVARD.EDU or FAX 617-495-7231 (subscriptions)
URL http://www.cfa.harvard.edu/iau/cbat.html  ISSN 0081-0304
Phone 617-495-7440/7244/7444 (for emergency use only)

S/2007 S 1, S/2007 S 2, AND S/2007 S 3
     Further to IAUC 8727, S. S. Sheppard, D. C. Jewitt, and J.
Kleyna have reported the discovery of three new satellites of
Saturn in data obtained earlier this year with the Subaru 8.2-m
reflector at Mauna Kea, aided by B. G. Marsden's ongoing linkages
and search ephemerides.  The astrometry and orbital data appear on
MPECs 2007-G38 and 2007-J09, showing orbital periods of 895, 793,
and 992 days for S/2007 S 1, S/2007 S 2, and S/2007 S 3,
respectively; the latter two objects have retrograde orbits.

(4951) IWAMOTO
     V. Reddy, Department of Earth System Science and Policy,
University of North Dakota, Grand Forks; R. Dyvig, Badlands
Observatory, Quinn, SD; P. Pravec and P. Kusnirak, Ondrejov
Observatory; A. Galad, L. Kornos, S. Gajdos, and J. Vilagi, Modra
Observatory; D. Pray, Carbuncle Hill Observatory, Greene, RI; W.
Cooney, J. Gross, and D. Terrell, Sonoita Research Observatory,
Sonoita, AZ; Yu. Krugly, Kharkiv Observatory; J. Ries, McDonald
Observatory; K. Archer, Ironwood Observatory, Oahu, HI; J. Oey,
Leura, N.S.W., Australia; M. Pikler and M. Husarik, Skalnate Pleso
Observatory; R. Durkee, Minneapolis, MN; F. Colas, Pic du Midi
Observatory; and A. Harris, Space Science Institute, report that
photometric observations obtained during 2006 Dec. 25.1 to 2007 Mar.
23.9 UT reveal that minor planet (4951) is a synchronous binary
system with a period of 118.0 +/- 0.2 hours.  A combined rotation
lightcurve has an amplitude of 0.34 mag, and superimposed mutual
events indicate a lower limit on a secondary-to-primary mean-
diameter ratio of 0.76.  An estimated mean absolute magnitude in
the Cousins R system of 13.26 +/- 0.05 and measured color index of
V-R = +0.48 +/- 0.03 give an absolute V magnitude of 13.74 +/- 0.06.
This yields estimated mean diameters for the two bodies of 4.0 and
3.5 km (uncertain by about 20 percent), assuming a geometric V
albedo of 0.20 +/- 0.07 for its 'S' classification from 'SMASS II'
visible spectroscopy.  The system's parameters are extraordinary in
comparison with other known small binaries, in terms of system
angular momentum and evolution to its present synchronous state;
thus, further observations are warranted.

     Further to IAUC 8806, G. Sostero reports that R-band exposures
by H. Mikuz with the Crni Vrh 0.6-m reflector on Feb. 13.85 UT
reveal a faint extension some 10"-12" long in p.a. about 345 deg.

                      (C) Copyright 2007 CBAT
2007 May 11                    (8836)            Daniel W. E. Green

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