EDP Sciences
Free access
Volume 391, Number 3, September I 2002
Page(s) 1133 - 1139
Section The solar system
DOI http://dx.doi.org/10.1051/0004-6361:20020903

A&A 391, 1133-1139 (2002)
DOI: 10.1051/0004-6361:20020903

Coordinated thermal and optical observations of Trans-Neptunian object (20 000)Varuna from Sierra Nevada

E. Lellouch1, R. Moreno2, J. L. Ortiz3, G. Paubert4, A. Doressoundiram1 and N. Peixinho1, 5

1  Observatoire de Paris, 5 place J. Janssen, 92195 Meudon, France
2  I.R.A.M. 300 Av. de la Piscine, 38406 St-Martin d'Hères Cedex, France
3  Instituto de Astrofísica de Andalucia, CSIC, Camino Bajo de Huetor 24, 18080 Granada, Spain
4  I.R.A.M. Avda. Divina Pastora 7, 18012 Granada, Spain
5  Centro de Astronomia e Astrofísica da Universidade de Lisboa, 1349-018 Lisboa, Portugal

(Received 11 June 2002 / Accepted 14 June 2002)

We report on coordinated thermal and optical measurements of trans-Neptunian object (20 000)Varuna obtained in January-February 2002, respectively from the IRAM 30-m and IAA 1.5 m telescopes. The optical data show a lightcurve with a period of $3.176 \pm 0.010$ hr, a mean  V magnitude of $20.37 \pm 0.08$ and a $0.42 \pm 0.01$ magnitude amplitude. They also tentatively indicate that the lightcurve is asymmetric and double-peaked. The thermal observations indicate a $1.12\pm 0.41$ mJy flux, averaged over the object's rotation. Combining the two datasets, we infer that Varuna has a mean 1060 +180-220 km diameter and a mean 0.038 +0.022-0.010 V geometric albedo, in general agreement with an earlier determination using the same technique.

Key words: kuiper belt -- planets and satellites: general -- techniques: photometric -- submillimeter

Offprint request: E. Lellouch, emmanuel.lellouch@obspm.fr

© ESO 2002