Geoscience Reference
In-Depth Information
first part of this article, we report our preliminary results concerning the
lightcurves of the twelve Karin family members, though detailed statistical
discussions will be presented in a separate paper.
4
Next, we move on to the
result of our multicolor observation of the largest member of this family,
(832) Karin. Since (832) Karin is the largest fragment of a recent asteroid
disruption, it is possible that this asteroid has both young and old surfaces
together: a young surface that was exposed from the interior of the parent
body by the family-forming disruption, and an old surface that used to be
the parent body surface exposed to space radiation over a long time. If the
mixture of these two surfaces is detected by our multicolor observation, it
could have significant implication for research on the evolution of asteroid
surface spectra.
We briefly report the lightcurves of several Karin family members in
Sec. 2. In Sec. 3 we describe our multi-color observations of (832) Karin in
2003 as well as in 2004. The method and results of our multicolor obser-
vations are summarized in this section. Section 4 goes to some discussions
and interpretation of the results.
2. Lightcurves of the Karin Family Asteroids
For our lightcurve observations of the Karin family asteroids, we have used
eight telescopes: The 90-inch Bok reflector at the Steward Observatory (AZ,
USA), the 1.8-m Vatican Advanced Technology Telescope (AZ, USA), the
1.5-m telescope at Maidanak Observatory (Uzbekistan), the 1-m telescope
at Lulin Observatory (Taiwan), the 1-m Schmidt telescope at Kiso Obser-
vatory (Japan), the 0.5-m telescope at the National Astronomical Obser-
vatory (Japan), the 0.4-m telescope at Fukuoka University of Education
(Japan), and the 0.25-m telescope at Miyasaka Observatory (Japan). We
used
R
-band filter all through the observations because asteroids are gen-
erally brightest in the
R
-band wavelength. Exposure time was 2-8 min so
that asteroids had the appearance of point sources. We also observed several
Landolt photometric standard stars
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to determine extinction coecients.
Photometric reduction and aperture photometry were performed using the
APPHOT/IRAF package. Magnitudes of the asteroid at different air masses
were corrected by the extinction coecient at each band. Asteroid bright-
ness was measured with respect to that of the field stars in the USNO-A2
catalogue in the same frame.
Lightcurves from the photometric data are constructed following the
procedure proposed by Harris and Lupishko.
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Principally it is an iterative
