TAOS Detected Occultation by an Asteroid
(21 Feb. 2004)
A bright star HIP 079407 (MV = 8.80) was occulted by
an asteroid (51) Nemausa (MV = 11.9, diameter = 150 km)
at around 18:55 21st Feb. 2004 (UTC).
This event was predicted by Dr. Sato with a maximal occultation duration
around 7.5 seconds.
Its shadow was expected to pass through the central part of Taiwan
where the TAOS site is located.
Using a special zipper mode operation,
TAOS telescope is able to identify this event.
Above picture is a low resolution version of part of the raw data
taken by TAOS B telescope.
The time interval is 0.5 seconds between the readout of two row blocks.
Each row block has a physical size of 2048 by 64 pixels
in this observation.
An occultation lasts for more than ten row blocks
(640 pixels in the vertical direction)
is clearly visible in the above picture.
A magnitude drop about 3.5 magnitude was detected.
The next picture is the enlarged version but rotated by 90 degrees clockwise.
This event was also recorded by Lulin One-meter Telescope (LOT)
which is right next to TAOS telescopes.
Observers at National Cheng-Kung University,
National Taiwan Normal University, and
Taipei Astronomical Museum pointed their telescopes
at the same target at the same time.
However, they detected no occultation signal.
TAOS enclosures were opened by local assistant.
Limit switches were temporarily disabled because of the low
elevation angle (around 30 degrees) of this event.
Both TAOS A and TAOS B telescopes were controlled remotely from Taipei.
Though, the image from TAOS A suffered from some autofocus problem.
It shows us the power of TAOS zipper mode operation
and the capability of this robotic system.
TAOS is a collaboration between Academia Sinica (Taiwan),
National Central University (Taiwan),
Lawrence Livermore National Laboratory (US),
Yonsei University (Korea),
and other individuals from
University of Pennsylvenia (US),
UC Berkeley (US), NASA Ames (US),
SLAC (US), University of Arizona (US).
Last Updated by S. K. King 2/26/2004
