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D. Rabinowitz, S. Tourtellotte (Yale University), B. Schaefer (Louisiana State University)
We are monitoring the B-, V-, and I-band light curves of Centaurs and trans-Neptunian objects (TNOs) to determine the wavelength dependence of their solar phase curves. Since February 2003 we have used the SMARTS 1.3m telescope at Cerro Tololo to make ~1800 photometric measurements of 15 bodies. The observations span the observable phase-angle range of each target and average 34 nights per target. Our preliminary analysis show that the phase curves are nearly all linear, but with slopes varying from 0.048 to 0.287 mag/deg depending on the target. Most of these phase curves also show no significant wavelength dependence, with the notable exception of a few that steepen with increasing wavelength. This wavelength dependence occurs only for the reddest targets in our sample with V-I > 1.1 mag. Two of these are (50000) Quaoar and 2002 AW197, large bodies known to have modest albedos (~0.1). Our results may indicate that both coherent backscatter and shadow hiding influence the phase brightening of such TNOs. Since the influence of coherent backscatter increases with surface reflectance, the wavelength dependence of the phase curves for the bodies with very red colors would result from an increase in the magnitude of the coherent backscatter at longer wavelengths relative to the contribution from shadow hiding.
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Bulletin of the American Astronomical Society, 36 #4
© 2004. The American Astronomical Soceity.