Photometric and spectroscopic observations of Sycorax, satellite of Uranus

Sycorax is the brightest of the ve 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 ma nd is rather flat over the near-infrared range. We were not able to reproduce the spectral behaviour of Sycorax using simple materials. A rotational eect is suggested to explain the shape of the spectrum. BVRIJ magnitudes have been measured over a period of 1 hour, with ve 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.

[1]  J. Luu.  CCD photometry and spectroscopy of the outer Jovian satellites , 1991 .

[2]  D. Jewitt,et al.  Optical-Infrared Spectral Diversity in the Kuiper Belt , 1998 .

[3]  Conicet,et al.  Capture of planetesimals by the giant planets , 1995 .

[4]  D. Tholen,et al.  Compositional Surface Diversity in the Trans-Neptunian Objects , 2000 .

[5]  J. Burns,et al.  The Discovery of Uranus XIX, XX, and XXI , 2000 .

[6]  J. Luu.  Spectral Diversity among the Nuclei of Comets , 1993 .

[7]  Edward Huntington Cobb,et al.  Geological Survey open-file reports of Alaska indexed by quadrangle , 1974 .

[8]  E. Karkoschka.  Rings and Satellites of Uranus: Colorful and Not So Dark☆☆☆ , 1997 .

[9]  D. Tholen,et al.  Spectrophotometric Observations of Edgeworth–Kuiper Belt Objects , 1999 .

[10]  J. Davies.  Physical Characteristics of Trans-Neptunian Objects and Centaurs , 2000 .

[11]  Sylvain Douté,et al.  A multilayer bidirectional reflectance model for the analysis of planetary surface hyperspectral images at visible and near‐infrared wavelengths , 1998 .

[12]  M. G. Parisi,et al.  CONSTRAINTS TO URANUS' GREAT COLLISION-II , 1997 .

[13]  T. Owen,et al.  The Composition of Centaur 5145 Pholus , 1998 .

[14]  J. Burns,et al.  Gas drag in primordial circumplanetary envelopes: A mechanism for satellite capture , 1979 .

[15]  C. V. Houten,et al.  Distant asteroids and outer Jovian satellites , 1979 .

[16]  Joseph Veverka,et al.  The composition of the Trojan asteroids , 1980, Nature.

[17]  F. Mannucci,et al.  Northern JHK Standard Stars for Array Detectors , 1998, astro-ph/9803153.

[18]  L. Colangeli,et al.  Optical constants of cosmic carbon analogue grains — I. Simulation of clustering by a modified continuous distribution of ellipsoids , 1996 .

[19]  M. W. Williams,et al.  Optical constants of organic tholins produced in a simulated Titanian atmosphere: From soft x-ray to microwave frequencies , 1984 .

[20]  J. Burns,et al.  Discovery of two distant irregular moons of Uranus , 1998, Nature.

[21]  W. Hartmann,et al.  Remote comets and related bodies: VJHK colorimetry and surface materials , 1982 .

[22]  D. Trilling,et al.  Red, Gray, and Blue: Near Infrared Spectrophotometry of Faint Moons of Uranus and Neptune , 2000 .