Sloan Digital Sky Survey Observations of Kuiper Belt Objects: Colors and Variability

Abstract

Colors of trans-Neptunian objects (TNOs) are used to study the evolutionary processes of bodies in the outskirts of the solar system and to test theories regarding their origin. Here I describe a search for serendipitous Sloan Digital Sky Survey (SDSS) observations of known TNOs and Centaurs. I present a catalog of SDSS photometry, colors, and astrometry of 388 measurements of 42 outer solar system objects. I find weak evidence, at the ≈ 2σ level (per trial), for a correlation between the g – r color and inclination of scattered disk objects and hot classical Kuiper Belt objects. I find a correlation between the g – r color and the angular momentum in the z direction of all the objects in this sample. These findings should be verified using larger samples of TNOs. Light curves as a function of phase angle are constructed for 13 objects. The steepness of the slopes of these light curves suggests that the coherent backscatter mechanism plays a major role in the reflectivity of outer solar system small objects at small phase angles. I find weak evidence for an anticorrelation, significant at the 2σ confidence level (per trial), between the g-band phase-angle slope parameter and the semimajor axis, as well as the aphelion distance, of these objects (i.e., they show a more prominent "opposition effect" at smaller distances from the Sun). However, this plausible correlation should be verified using a larger sample. I discuss the origin of this possible correlation and argue that if this correlation is real it probably indicates that "Sedna"-like objects have a different origin than other classes of TNOs. Finally, I identify several objects with large variability amplitudes.

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