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Article Dans Une Revue Astronomy and Astrophysics - A&A Année : 2011

Integral-field spectroscopy of (90482) Orcus-Vanth

Résumé


Aims: We seek to constrain the surface composition of the trans-Neptunian object (90482) Orcus and its small satellite Vanth, as well as their mass and density.
Methods: We acquired near-infrared spectra (1.4-2.4 mum) of (90482) Orcus and its companion Vanth using the adaptive-optics-fed integral-field spectrograph SINFONI mounted on Yepun/UT4 at the European Southern Observatory Very Large Telescope. We took advantage of a very favorable appulse (separation of only 4") between Orcus and the UCAC2 29643541 star (mR = 11.6) to use the adaptive optics mode of SINFONI, allowing both components to be spatially resolved and Vanth colors to be extracted independently from Orcus.
Results: The spectrum of Orcus we obtain has the highest signal-to-noise ratio to date, and we confirm the presence of H2O ice in crystalline form, together with the presence of an absorption band at 2.2 mum. We set an upper limit of about 2% to the presence of methane, and 5% for ethane. Since the methane alone cannot account for the 2.2 mum band, the presence of ammonia is suggested to the level of a couple of percent. The colors of Vanth are found to be slightly redder than those of Orcus, but the large measurement uncertainties prevent us from drawing any firm conclusions about the origin of the pair (capture or co-formation). Finally, we reset the orbital phase of Vanth around Orcus, and confirm the orbital parameters derived by Brown and collaborators.

Dates et versions

hal-03732565 , version 1 (21-07-2022)

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Benoît Carry, Daniel Hestroffer, Francesca E. Demeo, Audrey Thirouin, Jerôme Berthier, et al.. Integral-field spectroscopy of (90482) Orcus-Vanth. Astronomy and Astrophysics - A&A, 2011, 534, pp.115. ⟨10.1051/0004-6361/201117486⟩. ⟨hal-03732565⟩
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