Titania's Radius and an Upper Limit on its Atmosphere from the Sep. 8, 2001 Stellar Occultation
Résumé
On September 8, 2001, the largest of Uranian moons, Titania, occulted V = 7.2, K0 III Hipparcos-catalog star HIP 106829. The star's unusual brightness allowed more than a hundred stations to monitor this unique event over three continents. The main goals of the observations were to (i) determine Titania's radius and possible oblateness ; (ii) determine Titania's offset with respect to the DE405 URA027 ephemeris ; (iii) search for an atmosphere. Our new analysis provides ground pressure upper limits for a Titania's equilibrium atmosphere at typical levels of ~10 nbar. This value, a factor of ~103 less than current atmospheres of Pluto or Triton, is encouraging in the context of search for atmospheric signature in a ground-based stellar occultation by a KBO.