[Show abstract][Hide abstract] ABSTRACT: The Karin family is a very young asteroid family created by an asteroid
breakup 5.8 Myr ago. Since the members of this family probably have not
experienced significant orbital or collisional evolution yet, it is possible
that they still preserve properties of the original family-forming event in
terms of their spin state. As we carried out a series of photometric
observations of the Karin family asteroids, here we report an analysis result
of lightcurves including the rotation period of eleven members. The mean
rotation rate of the Karin family members turned out to be much lower than
those of NEAs or smaller MBAs (diameter D<12 km), and even lower than that of
larger MBAs (D>130 km). We investigated a correlation between the peak-to-peak
variation magnitude reduced to zero solar phase angle and the rotation period
of the eleven Karin family asteroids, and found a possible trend that elongated
members have lower spin rate, and less elongated members have higher spin rate.
However, this has to be confirmed by another series of future observations.
[Show abstract][Hide abstract] ABSTRACT: Asteroid (832) Karin is the largest member of the Karin family which was re-cently identified and estimated to be 5.8 Myr old by Nesvorn et al. (2002) with a sophisticated numerical integration technique. The Karin family is regarded as an outcome of a collision in such recent times. In order to make clear the physical aspect of this family-forming event, we performed photometric observations of Karin from July to September, 2003. We report here its lightcurve and colors in optical bands. The rotational period of asteroid Karin was determined to be 18.346 ± 0.096 hr. Its absolute magnitude (H) and the slope parameter (G) of the phase curve at R-band are 11.49 ± 0.02 and 0.19 ± 0.04, respectively. Based on our color observations, we confirmed that this asteroid belongs to the S-type asteroid group. Moreover, we prob-ably found that there is a color variation over the surface of Karin. We infer that the color variation is due to the difference between the fresh surface excavated by the family-forming disruption and the weathered surface exposed to the space radiation and particle bombardment for a long time.
Publications- Astronomical Society of Japan 12/2004; 56. · 2.44 Impact Factor