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S.D. Kern (MIT/U. Arizona), D.W. McCarthy (U. Arizona), M.W. Buie (Lowell Obs.), R.H. Brown, H. Campins, M. Rieke (U. Arizona)
Strong and variable absorption features on the surface of the Centaur 8405 Asbolus (1995 GO) indicate a significantly inhomogeneous surface. Our 1-2 micron spectra were obtained by HST/NICMOS and have been modeled by water ice mixed with additional unknown constituents. The observed spectra vary from a complicated absorption spectrum to a nearly featureless continuum with a red slope. The continuum spectrum agrees with ground based observations from Keck (Brown, M. E., 2000 AJ). The integrated flux during the 1.7 hour interval of observation is consistent with previous lightcurve measurements. The accepted rotation period of 8.9351 hours (Davies et al. 1998, Icarus, 134, 213) assumes a shape dominated lightcurve, while our observations indicate that the lightcurve may in fact be dominated by albedo variations. This suggests that Asbolus may be rotating faster (4.47 hours) than previously suspected. Asbolus is one of twelve Centaurs and Kuiper Belt objects which we have observed with HST/NICMOS to establish a uniform spectral library for understanding and classifying such objects.
Support for this work was provided by NASA through grant GO-07822.01-96A from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Incorporated, under NASA contract NAS5-26555. We also acknowledge support from NASA project NAG-53359.
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