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IAUC 7588: S/2001 (87) 1; JUPITER I (IO); XTE J1543-568

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                                                  Circular No. 7588
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Mailstop 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
IAUSUBS@CFA.HARVARD.EDU or FAX 617-495-7231 (subscriptions)
CBAT@CFA.HARVARD.EDU (science)
URL http://cfa-www.harvard.edu/iau/cbat.html  ISSN 0081-0304
Phone 617-495-7440/7244/7444 (for emergency use only)


S/2001 (87) 1
     M. E. Brown and J. L. Margot, California Institute of
Technology, report the discovery of a satellite to (87) Sylvia.
The projected separation between primary and secondary was 0".59
(1200 km) in p.a. 97 deg on H-band images obtained on Feb. 18.5 UT
using the adaptive-optics system at the 10-m W. M. Keck II
telescope on Mauna Kea.  Little relative motion was apparent in
images obtained an hour apart (upper limit 0".02).  The brightness
ratio was measured to be 420 +/- 70, implying a about 1:20 ratio of
diameters.  Confirming observations were obtained at the Keck II
telescope by I. de Pater and H. Roe on Feb. 19.4, 20.4, and 22.4,
and the data indicate an orbital period on the order of 4 days.


JUPITER I (IO)
     I. de Pater, F. Marchis, and H. Roe, University of California
at Berkeley; B. Macintosh, Lawrence Livermore National Laboratories;
and S. Acton and D. Le Mignant, Keck Observatory, report an extreme
volcanic outburst on Jupiter I:  "We observed Io on Feb. 19, 20,
and 22 UT with the Adaptive Optics system on the Keck II telescope
in the bands J, H, and K'.  On Feb. 20 and 22, we observed the
hemisphere that approximately faced Jupiter.  On Feb. 22, the
region to the northeast of Loki was very bright in all three bands
(K' about 5), being detectable even against the sunlit disk of Io.
The hot spot is located at west longitude 334 +/- 3 deg and north
latitude 40 +/- 3 deg, close to the position of Surt.  This region
did not show any discernible activity on Feb. 20.  From the 3-band
photometry, the temperature is estimated to be about 1000-1100 K;
an H-band spectrum taken at the same time suggests a temperature of
about 1700-1800 K.  We encourage follow-up observations to
determine the time evolution of this outburst."


XTE J1543-568
     R. Kaptein, BeppoSAX Science Operation Center, Rome, and Space
Research Organization Netherlands (SRON), Utrecht; J. J. M. in 't
Zand, Astronomical Institute, Utrecht University, and SRON; and J.
Heise, SRON, write:  "The Wide Field Cameras on BeppoSAX have for
the first time detected XTE J1543-568.  In an observation with unit
1 during Feb. 5.3-8.7 UT, the average flux was about 9 mCrab (2-9
keV) at position R.A. = 15h44m01s, Decl. = -56o45'.9 (equinox
2000.0; 99-percent-confidence error radius 2'.0).  The position
provides an improvement by a factor of 4 in accuracy (cf. IAUC
7369)."

                      (C) Copyright 2001 CBAT
2001 February 23               (7588)            Daniel W. E. Green

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