Astrophysics, abstract
astro-ph/0602631

From: Sonia Fornasier [view email]

Date: Tue, 28 Feb 2006 19:29:25 GMT (58kb)

First albedo determination of 2867 Steins, target of the Rosetta mission

Authors: S. Fornasier, I. Belskaya, M. Fulchignoni, M. A. Barucci, C. Barbieri

Comments: 4 pages, 4 figures, letter accepted for pubblication on A&A

We present the first albedo determination of 2867 Steins, the asteroid target o f the Rosetta space mission together with 21 Lutetia. The data were obtained in polarimetric mode at the ESO-VLT telescope with the FORS1 instrument in the V and R filters. Observations were carried out from Jun e to August 2005 covering the phase angle range from 10.3 deg. to 28.3 deg., allowing the determination of the asteroid albedo by the well known experimenta l relationship between the albedo and the slope of the polarimetric curve at th e inversion angle. The measured polarization values of Steins are small, confirming an E-type cla ssification for this asteroid, as already suggested from its spectral propertie s. The inversion angle of the polarization curve in the V and R filters is resp ectively of 17.3 +/-1.5deg. and 18.4+/-1.0 deg., and the corresponding sl ope parameter is of 0.037+/-0.003 %/deg and 0.032+/-0.003 %/deg. On the basis of its polarimetric slope value, we have derived an albedo of 0.45 +/-0.1, that gives an estimated diameter of 4.6 km, assuming an absolute V ma gnitude of 13.18 mag.

http://arxiv.org/abs/astro-ph/0602631