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Proposal Information for 2004A-0361


PI: Beatrice E.A. Mueller, NOAO, muller@noao.edu
Address: NTSS, 950 N Cherry Ave, Tucson, AZ 85719, U.S.A.

CoI: Nalin H. Samarasinha, NOAO

Title: Color Observations of Large Trans-Neptunian Objects as a Function of Rotational Phase

Abstract: Observationally there is widespread interest in comparing different classes of TNOs in color space. Currently, there are claims and counter claims of color differences and trends among different classes of TNOs (e.g., Tegler & Romanishin 2003, Boehnhardt \it et al. 2002, Jewitt & Luu 2001, Davies \it et al. 2000). Peixinho \it et al. (2003) find a clear bimodality for Centaur colors. Barucci \it et al. (2003), Hainaut & Delsanti (2002), and Doressoundiram \it et al. (2001) note the bimodal color distribution for centaurs but more data are needed to exclude that this is an artifact of the small numbers of available Centaur colors. We propose to observe colors of several bright (V brighter than 21.5mag) trans-Neptunian objects (TNOs) as a function of rotational phase, therefore complementing ongoing programs at bigger telescopes which primarily observe fainter objects. This approach is necessary because many TNOs show large peak to peak variations in their lightcurves and measured colors of the same objects from different authors (see Jewitt & Luu 2001) often lie outside the formal errors of each other. In addition, the measured colors are mostly at random rotational phases despite the evidence that some TNOs show color differences as a function of rotational phase. We will concentrate on the Centaurs to increase the data base for accurate colors to improve the statistics to confirm or rule out a bimodal distribution in color.


National Optical Astronomy Observatory, 950 North Cherry Avenue, P.O. Box 26732, Tucson, Arizona 85726, Phone: (520) 318-8000, Fax: (520) 318-8360



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