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IAUC 8389: S/2004 S 1, S/2004 S 2; (854); 2004dj

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                                                  Circular No. 8389
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://cfa-www.harvard.edu/iau/cbat.html  ISSN 0081-0304
Phone 617-495-7440/7244/7444 (for emergency use only)

S/2004 S 1 AND S/2004 S 2
     C. C. Porco, CICLOPS, Space Science Institute, Boulder; and
the Cassini Imaging Science Team (cf. Porco et al. 2004, Science,
in preparation) report the discovery of two new satellites of
Saturn, S/2004 S 1 and S/2004 S 2, both orbiting between Saturn I
(Mimas) and Saturn II (Enceladus).  Revolution periods, orbital
semimajor axes, and estimated satellite diameters are as follows:
S/2004 S 1, 1.01 days, 194000 km, 3 km; S/2004 S 2, 1.14 days,
211000 km, 4 km.  There is a slight possibility that S/2004 S 1 is
identical with S/1981 S 14, observed in a single Voyager image on
1981 Aug. 23 (IAUC 6162), but this is still under investigation.
Both orbits appear to be approximately circular and equatorial.
Estimated diameters assume disk-integrated reflectivities of 0.15
at a phase angle of 67 degrees.  Visual magnitudes seen from the
earth are estimated to be in the range of about 22-23.  The objects
were first discovered in imaging sequences taken on 2004 June 1
that were specifically designed to search for new satellites in the
inner saturnian system.  In these sequences, S/2004 S 1 was
observed over 6.0 hr, while S/2004 S 2 was observed over 9.3 hr.
All exposures were 4.6 s and taken with the narrow-angle camera
through the clear filters (Porco et al. 2004, Space Sci. Rev., in
press).  S/2004 S 1 was subsequently found in other Cassini narrow-
angle camera images taken three weeks earlier with exposure times
of 18 s.

     R. Behrend, Geneva Observatory; L. Bernasconi, Les Engarouines,
France; A. Klotz, TAROT, Observatoire de Haute-Provence; and R.
Durkee, Minneapolis, MN, report that photometric observations of
(854), obtained during July 16-19, show a regularly shaped light
curve with period 1.565 day and amplitude 0.33 mag, with sharp
attenuations characteristic of mutual-eclipse/occultation events
(observed at minima of the regular light curve) having depth about
0.7 mag and duration about 3.7 hr -- strongly suggesting that (854)
is a binary system with properties similar to those of (1089),
(1313), and (4492).  The first complete event occurred on July
16.92 UT.

SUPERNOVA 2004dj IN NGC 2403
     Visual magnitude estimates:  Aug. 7.899 UT, 11.8 (R. J. Bouma,
Groningen, The Netherlands); 10.89, 12.1 (A. Mizser, Budapest,
Hungary); 13.916, 11.9 (K. Hornoch, Lelekovice, Czech Republic).

                      (C) Copyright 2004 CBAT
2004 August 16                 (8389)            Daniel W. E. Green

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