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IAUC 8432: Sats, RINGS OF SATURN; 2004fc

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                                                  Circular No. 8432
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)

     C. C. Porco, CICLOPS, Space Science Institute, Boulder; and
the Cassini Imaging Science Team (cf. IAUC 8389) report the
discovery of S/2004 S 5, a satellite orbiting in the region of
Saturn III (and Tethys) and Saturn IV (Dione).  The new satellite
was seen in a series of six consecutive narrow-angle, clear-filter
frames taken on Oct. 21, spanning 3 hr; it was also seen in two
wide-angle images taken 12 days later.  The spread of observations
around the orbit is too short to report the orbital distance and
configuration with confidence; if S/2004 S 5 is in a near-
equatorial and near-circular orbit, it may be a coorbital satellite
of Dione.  S/2004 S 5 is approximately 5 km across.  Also, S/2004 S
3 (cf. IAUC 8401) was recovered at phase angle 64 deg in a Cassini
image taken on Oct. 17 (118 days after the discovery sequence of
June 21).  This puts the revolution period and semimajor axis at
0.62095 day and 140580 km.  It is clear now that S/2004 S 3 is not
the same object as S/2004 S 4 (IAUC 8401).  Another object, S/2004
S 6, is also seen in the F-ring region, skirting the inner edge of
the tenuous dust sheet that surrounds the F ring, in a sequence of
movie images taken of that region at very high phase (153 deg) over
a period of 1 hr on Oct. 28; its approximate orbital period and
semimajor axis are 0.61 day and 140000 km.   The fact that the
object was seen at 153 deg phase may indicate that it is a clump
with associated dust that is visible at high phase angles.  It is
possible, but not likely, that S/2004 S 6 is the same object as
S/2004 S 4.  More observations of this region, aimed at imaging
orbiting satellites, are planned.  A new narrow ring in the F-ring
region, R/2004 S 2, is approximately 300 km wide and is located at
138900 km between the 'Atlas' ring (R/2004 S 1; IAUC 8401) and the
orbit of Saturn XVI (Prometheus).

     M. Salvo, B. Schmidt and S. Keller, Australian National
University (ANU), report that a spectrogram (range 400-700 nm) of
SN 2004fc (cf. IAUC 8422), obtained with the ANU 2.3-m telescope (+
Double-Beam Spectrograph) at Siding Spring on Oct. 22.56 UT, shows
it to be a type-II supernova before maximum light.  The spectrum
consists of a blue continuum with weak P-Cyg Balmer lines.
Adopting the NASA/IPAC Extragalactic Database recession velocity of
1829 km/s for the host galaxy, the expansion velocity derived from
the minimum of the H_beta line is 9700 km/s.

                      (C) Copyright 2004 CBAT
2004 November 8                (8432)            Daniel W. E. Green

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