A Binary System was Resolved in the Occultation by (87) Sylvia
(18 December, 2006)
Light Curves (observed both at Lulin and in Taichung City)
(Picture Courtesy: Kiwi Zhang and Chilong Lin)
The catalogued star TYC 1947-00293-1 (V = 10.0) was occulted by
the asteroid (87) Sylvia (V = 12.6, size = 192x132x116 km)
at around 19:00 UT, 2006 December 18.
This event was
predicted
with a maximal occultation duration around 23.4 seconds.
Its shadow was expected to pass through the northern half of Taiwan
where the TAOS site (Lulin) is near the southern edge.
The asteroid (87) Sylvia is known as
a triple asteroidal system,
that is very special (other than the Pluto and Charon quartet)
in our Solar System.
Using a special zipper mode operation,
two working TAOS telescopes (TAOS A and TAOS B)
are able to identify this event clearly
while running in synchronous mode.
A 40-cm telescope at Lulin (running by Hung-Chin Lin)
and a 10-inch telescope (F/4, with WATEC-902H CCD &
was recorded by SHARP-Z5U DV)
in Taichung City (running by Dr. Chilong Lin)
observed this event at the same time.
(Here
is a map of Taichung-Lulin area.)
There was no satellite occultation event detected.
However, both the TAOS telescopes and the 40-cm telescope
observed a ~32% flux drop (nearly 0.4 magnitudes)
lasted for about 20.5 seconds.
The Taichung team saw two (32% and 57%) flux drops
separated by two or three video frames.
The duration of these two flux drops are about 23.9 seconds and 10.8 seconds
respectively.
All flux drops measured are consistent with the assumption that
the background star is really a binary system.
Their brightness ratio is about 1.8.
The
spectrum
(picture courtesy: National Central University)
of this binary system shows that the primary should be an F-type star.
This is a previous unknown binary system
that was first resolved by this observation.
TAOS telescopes were controlled remotely from Taipei
and were running in synchronous mode by S. K. King.
The TAOS collaboration includes
Academia Sinica (Taiwan),
Harvard-Smithsonian Center for Astrophysics (US),
Lawrence Livermore National Laboratory (US),
National Central University (Taiwan),
Yonsei University (Korea),
and other individuals from
University of Pennsylvenia (US),
UC Berkeley (US), NASA Ames (US),
SLAC (US), and University of Arizona (US).
Prediction
The detail of this event is available at
Steve Preston's webpage
on Asteroid Occultation Updates.
Here is the
predicted path plot
and an enlarged view.
GIF Movie
GIF animations of this occultation observed by the TAOS A and TAOS B
are available
here
(prepared by Andrew Wang, ASIAA).
The total time included in these GIF animations is about 51 seconds
for each telescope.
Light Curves
- observed by TAOS A and TAOS B at Lulin (from Kiwi Zhang):
- observed by a 40-cm telescope at Lulin (from Soumen Mondal):
- observed by Dr. Lin in Taichung City (from Kiwi Zhang):
- expressed in flux:
JPG
and
PDF
TAOS homepage
Last Updated by S. K. King 19 March, 2007
