Electronic Telegram No. 3398
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
CBAT Director:  Daniel W. E. Green; Hoffman Lab 209; Harvard University;
 20 Oxford St.; Cambridge, MA  02138; U.S.A.
e-mail:  cbatiau@eps.harvard.edu (alternate cbat@iau.org)
URL http://www.cbat.eps.harvard.edu/index.html
Prepared using the Tamkin Foundation Computer Network


DETECTION OF A STELLAR OCCULTATION BY (87) SYLVIA I (ROMULUS)
     J. Berthier, Institut de Mecanique Celeste et de Calcul des Emerides,
Institut de Mecanique Celeste et de Calcul des Emerides (IMCCE); E. Frappa,
Euraster; A. Klotz, Universite de Toulouse, Centre National de la Recherche
Scientifique, Institut de Recherche en Astrophysique et Planetologie; and J.
Lecacheux, Laboratoire d'Etudes Spatiales et d'Instrumentation en
Astrophysique, Observatoire de Paris, on behalf of the European
asteroidal-occultation network of observers, report the successful stellar
occultations by the triple minor-planet system (87) Sylvia on Jan. 6.06742 UT
of the star HD 244394 (mag 10.8).  Astrometric positions of the star were
refined from observations collected on 2012 Dec. 1 by P. Descamps (IMCCE) with
the 0.6-m Makes telescope at Reunion Island (R.A. = 5h31m27s.251, Decl. =
+27d29'19".19, equinox 2000.0).  The occultation paths made by the satellites
of (87) Sylvia were predicted by F. Vachier (IMCCE) and F. Marchis (SETI
Institute, IMCCE) from adaptive-optics observations collected between 2001 and
2011 and using the dynamical model analysis of Vachier et al. (2012, A.Ap. 543,
A68, 9).  Among 33 reports (published on the Euraster website; see URL
http://www.euraster.net/results/2013/index.html#0106-87), twelve positive
chords of the occultation by the primary, lasting between 4 s and 26 s,
were successfully reported.  Observations recorded by E. Frappa and A. Klotz
(TAROT north robotic telescope at Calern observatory), by the Occultation Team
of Observatoire de la Cote d'Azur (P. Bendjoya, L. Abe, O. Suarez, and P.
Tanga; 1-m C2PU telescope at Calern and 0.35-m telescope at Tourrette Levens),
by M. Devogele (Institut d'Astrophysique de l'Universite de Liege, C2PU), and
by P. Dubreuil with a 0.2-m telescope at Aspremont, permitted the detection of
a brief (0.5-2 s) stellar occultation at the expected position of the large
satellite Romulus.  Preliminary analysis of the Romulus chords suggest that
the shape of the satellite is extremely elongated or irregular (a/b > 2), with
a major axis oriented toward the primary, and an equivalent diameter between
18 and 28 km.  S. Preston (IOTA) posted the path of an occultation of a star
of V magnitude 12.4 by the Sylvia triple system on 2013 Feb. 4.86 (see website
URL http://www.asteroidoccultation.com/2013_02/0204_87_29471.htm).  The
expected path of Romulus is available, and additional observations are
strongly encouraged.


NOTE: These 'Central Bureau Electronic Telegrams' are sometimes
      superseded by text appearing later in the printed IAU Circulars.

                         (C) Copyright 2013 CBAT
2013 February 4                  (CBET 3398)              Daniel W. E. Green