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A&A 420, 383-388 (2004)
DOI: 10.1051/0004-6361:20034507

A study of Trans-Neptunian object 55636 (2002 TX $\mathsf}$)

J. L. Ortiz1, A. Sota1, R. Moreno2, E. Lellouch3, N. Biver3, A. Doressoundiram3, P. Rousselot4, P. J. Gutiérrez1, 5, I. Márquez1, R. M. González Delgado1 and V. Casanova1

1  Instituto de Astrofísica de Andalucía, CSIC, Apt 3004, 18080 Granada, Spain
2  I.R.A.M., 300 rue de la Piscine, 38406 St-Martin d'Hères Cedex, France
3  Observatoire de Paris, 5 place J. Jansen, 92195 Meudon, France
4  Observatoire de Besançon, BP 1615, 25010 Besançon Cedex, France
5  Laboratoire d'Astrophysique de Marseille, Traverse du Siphon, BP 8, 13376 Marseille Cedex 12, France

(Received 13 October 2003 / Accepted 3 March 2004 )

Abstract
We report on physical properties of the bright Trans-Neptunian Object 2003 TX 300 based on a large set of observations taken in different wavelength ranges. Broad band CCD observations aimed at studying the short-term rotational variability show a low amplitude periodic signal of $7.89 \pm 0.03$ h. We cannot yet determine whether the lightcurve is single-peaked (i.e. the rotation period would be 7.89 h) or double-peaked (i.e. the actual spin period would be 15.78 h). From a sinusoidal fit, the peak to peak amplitude of the brightness changes is $0.09 \pm 0.08$ mag. If the brightness changes are due to irregular shape, this amplitude implies a minimum axial ratio of 1.09. BVRI photometry indicates similar colors as other large Kuiper Belt members, with $B-V = 0.64 \pm 0.04$, $V-R = 0.40 \pm 0.07$, and $R-I = 0.22 \pm 0.05$. Thermal observations at 250 GHz (1.2 mm) result in no confident detection of the body, with a measured flux of $0.22 \pm 0.51$ mJy. Combining all the data and using the same thermophysical model as in Lellouch et al. (2002) we find (at a 3- $\sigma$ confidence level) a lower limit for the geometric albedo ( pv>0.06) and an upper limit for the size of this object ( D< 1110 km). A more relaxed 2- $\sigma$ confidence level implies a diameter D< 907 km and an albedo pv> 0.08, which is significantly higher than the typical 0.04 cometary value and also higher than that of Varuna.


Key words: minor planets, asteroids -- Kuiper Belt

Offprint request: J. L. Ortiz, ortiz@iaa.es




© ESO 2004


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