A&A 376, 310-315 (2001)
DOI: 10.1051/0004-6361:20010934

Photometric and spectroscopic observations of Sycorax, satellite of Uranus

J. Romon¹, C. de Bergh¹, M. A. Barucci¹, A. Doressoundiram¹, J.-G. Cuby², A. Le Bras^{1, 3}, S. Douté⁴ and B. Schmitt<sup>4

1</sup>  Observatoire de Paris, Meudon, France
²  ESO, Chile
³  IAS, Orsay, France
⁴  Lab. de Planétologie de Grenoble, St Martin d'Hères, France

(Received 9 May 2001 / Accepted 26 June 2001)

Abstract
Sycorax is the brightest of the five irregular Uranian satellites recently discovered. These satellites are supposed to be captured bodies. We present visible and near-infrared photometry, as well as near-infrared spectroscopy of Sycorax. The overall shape of the spectrum is quite puzzling: it has a red slope in the visible (such as Centaurs and Transneptunian objects), whereas the reflectivity strongly decreases beyond 1 m and is rather flat over the near-infrared range. We were not able to reproduce the spectral behaviour of Sycorax using simple materials. A rotational effect is suggested to explain the shape of the spectrum. BVRIJ magnitudes have been measured over a period of 1 hour, with five V measurements which do not show any strong variation. So only a strong change in the magnitude between the V measurements and the J measurement (30 min later) could explain the shape of the spectrum, but further investigation is required to conclude.

Key words: planets and satellites: general -- planets and satellites: individual: Sycorax

Offprint request: J. Romon, jennifer.romon@obspm.fr

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