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Astronomical Journal, (2004), 127, 3023-3033 Scott S. Sheppard and David Jewitt Institute for Astronomy, University of Hawaii 2680 Woodlawn Drive, Honolulu, HI 96822 sheppard@ifa.hawaii.edu, jewitt@ifa.hawaii.edu Extensive time-resolved observations of Kuiper Belt object 2001 QG298 show a lightcurve with a peak-to-peak variation of 1.14 +-0.04 magnitudes and single-peaked period of 6.8872 +- 0.0002 hr. The mean absolute magnitude is 6.85 magnitudes which corresponds to a mean effective radius of 122 (77) km if an albedo of 0.04 (0.10) is assumed. This is the first known Kuiper Belt object and only the third minor planet with a radius > 25 km to display a lightcurve with a range in excess of 1 magnitude. We find the colors to be typical for a Kuiper Belt object (B-V = 1.00 +- 0.04, V-R = 0.60 +- 0.02) with no variation in color between minimum and maximum light. The large light variation, relatively long double-peaked period and absence of rotational color change argue against explanations due to albedo markings or elongation due to high angular momentum. Instead, we suggest that 2001 QG298 may be a very close or contact binary similar in structure to what has been independently proposed for the Trojan asteroid 624 Hektor. If so, its rotational period would be twice the lightcurve period or 13.7744 +- 0.0004 hr. By correcting for the effects of projection, we estimate that the fraction of similar objects in the Kuiper Belt is at least 10% to 20% with the true fraction probably much higher. A high abundance of close and contact binaries is expected in some scenarios for the evolution of binary Kuiper Belt objects.
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Download a PDF version of the 2001 QG298 paper shepjewQG298.pdf (PDF) -> All text, figures, and tables in one file
See the paper on our first sample of 22 Kuiper Belt Objects variability here
See the paper on our second sample of 11 more Kuiper Belt Objects variability observations here
This is Figure 5 in the paper. Blue stars represent KBOs, Black circles represent large asteroids and purple squares show other extreme minor planets. Region A: the observed variations are best explained by albedo, elongation or binaries. Region B: the observed variations are best explained by rotational elongation of the object. Region C: the observed variations are best explained by binary objects.
This is Figure 3 in the paper. It shows the double peaked light curve of 2001 QG298.
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