The mutual orbit, mass, and density of the large transneptunian binary system Varda and Ilmarë
Abstract
From observations by the Hubble Space Telescope, Keck II Telescope, and Gemini North Telescope, we have determined the mutual orbit of the large transneptunian object (174567) Varda and its satellite Ilmarë. These two objects orbit one another in a highly inclined, circular or nearcircular orbit with a period of 5.75 days and a semimajor axis of 4810 km. This orbit reveals the system mass to be (2.664 ± 0.064) × 10^{20} kg, slightly greater than the mass of the second most massive mainbelt asteroid (4) Vesta. The dynamical mass can in turn be combined with estimates of the surface area of the system from Herschel Space Telescope thermal observations to estimate a bulk density of 1.24_{0.35}^{+0.50}^{g cm  3} . Varda and Ilmarë both have colors similar to the combined colors of the system, BV = 0.886 ± 0.025 and VI = 1.156 ± 0.029.
 Publication:

Icarus
 Pub Date:
 September 2015
 DOI:
 10.1016/j.icarus.2015.04.036
 arXiv:
 arXiv:1505.00510
 Bibcode:
 2015Icar..257..130G
 Keywords:

 Kuiper belt;
 Transneptunian objects;
 Satellites;
 general;
 Hubble Space Telescope observations;
 Astrometry;
 Astrophysics  Earth and Planetary Astrophysics
 EPrint:
 16 pages, 4 tables, 6 figures, in press in Icarus