IAUC 3593: Sats OF SATURN; PKS 0735+178 AND 3C 371
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Read IAUC 3594
Circular No. 3593
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Postal Address: Central Bureau for Astronomical Telegrams
Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
TWX 710-320-6842 ASTROGRAM CAM Telephone 617-864-5758
SATELLITES OF SATURN
B. A. Smith, Lunar and Planetary Laboratory, reports that observations
by S. M. Larson and J. W. Fountain with the 1.5-m Catalina
reflector and new focal-plane coronagraph on Apr. 1.25 UT
showed 1980 S 6 ('Dione B') to lead Dione (Saturn IV) by 48o.1 +/- 0o.2,
in close agreement with the prediction on IAUC 3572. Further, an
unidentified satellite, designated 1981 S 1, with motion indistinguishable
from that of Enceladus (Saturn II), was recorded five
times during Apr. 1.27-1.32. Differential coordinates with respect
to the center of Saturn on Apr. 1.3003 UT were: Delta R.A. = +35".7 +/- 0".3,
Delta Decl. = +1".9 +/- 0".3. The object appears to be embedded in the E ring.
However, if it is actually located just outside the E ring, the satellite,
estimated at mv ~ 18, could be controlling the particle
distribution in the core of the E ring.
C. Veillet, CERGA, describing observations made on IIIa-J
plates at the direct Cassegrain focus of the 1.54-m Danish telescope
at the European Southern Observatory, notes that 31 observations
of 1980 S 6 during six nights Apr. 6-14 yield a mean separation
from Dione of 47o.89 +/- 0o.24 (p.e.). An unidentified satellite,
designated 1981 S 2, observed during six consecutive nights (Apr. 9-14)
has the following orbital elements: P = 1.8821 days, greatest
apparent eastern elongation = 1981 Apr. 11.1267 UT, 47".19 from the
center of Saturn. These elements fit the 41 available positions
within 0".35 (s.d.). 1981 S 2 may correspond to one or more of 1980
S 13, S 24 and S 25; its magnitude is at least 17. The above orbit
is very close to that of Tethys (Saturn III). If 1981 S 2 is supposed
to move in Tethys' orbit, its longitude difference from
Tethys is ~ 57o.9, close to the Saturn:Tethys L5 libration point.
PKS 0735+178 AND 3C 371
H. R. Miller, Georgia State University, writes that the BL Lac
object PKS 0735+178 and the N galaxy 3C 371 (which is related to
the BL Lac class of objects) are currently in a bright phase. The
following V magnitudes of PKS 0735+178 were obtained with the 1.3-m
telescope at Kitt Peak National Observatory: Mar. 29, 15.03; Mar.
30, 15.10; Mar. 31, 15.13; Apr. 1, 15.12. Corresponding V magni-
tudes of 3C 371 were: Mar. 31, 14.38; Apr. 1, 14.30. Both objects
have a history of optical variability, and spectrographic and radio
observations at this time would be particularly desirable.
1981 April 16 (3593) Brian G. Marsden
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