G. Benedetti-Rossi

TL;DR: Observations from multiple Earth-based observatories of Haumea passing in front of a distant star (a multi-chord stellar occultation) report the presence of a ring with an opacity of 0.5, which constrains the three-dimensional orientation of Haumesa and its triaxial shape, which is inconsistent with a homogeneous body in hydrostatic equilibrium.

TL;DR: In this paper, the authors present results from a multi-chord Pluto stellar occultation observed on 29 June 2015 from New Zealand and Australia, which occurred only two weeks before the NASA New Horizons flyby of the Pluto system and serves as a useful comparison between ground-based and space results.

TL;DR: In this paper, the authors present results derived from the first multi-chord stellar occultation by the trans-Neptunian object (229762) 2007 UK$ 126, observed on 2014 November 15.

TL;DR: In this paper, a central flash observed on 2015 June 29 is consistent with New Horizons REX profiles, provided that large diurnal temperature variations (not expected by current models) occur over Sputnik Planitia; and/or hazes with tangential optical depth of ~0.3 are present at 4-7 km altitude levels.

Abstract: The prediction of stellar occultations by Transneptunian objects and Centaurs is a difficult challenge that requires accuracy both in the occulted star position as for the object ephemeris. Until now, the most used method of prediction involving tens of TNOs/Centaurs was to consider a constant offset for the right ascension and for the declination with respect to a reference ephemeris. This offset is determined as the difference between the most recent observations of the TNO and the reference ephemeris. This method can be successfully applied when the offset remains constant with time. This paper presents an alternative method of prediction based on a new accurate orbit determination procedure, which uses all the available positions of the TNO from the Minor Planet Center database plus sets of new astrometric positions from unpublished observations. The orbit determination is performed through a numerical integration procedure (NIMA), in which we develop a specific weighting scheme. The NIMA method was applied for 51 selected TNOs/Centaurs. For this purpose, we have performed about 2900 new observations during 2007-2014. Using NIMA, we succeed in predicting the stellar occultations of 10 TNOs and 3 Centaurs between 2013 and 2015. By comparing the NIMA and JPL ephemerides, we highlighted the variation of the offset between them with time. Giving examples, we show that the constant offset method could not accurately predict 6 out of the 13 observed positive occultations successfully predicted by NIMA. The results indicate that NIMA is capable of efficiently refine the orbits of these bodies. Finally, we show that the astrometric positions given by positive occultations can help to further refine the orbit of the TNO and consequently the future predictions. We also provide the unpublished observations of the 51 selected TNOs and their ephemeris in a usable format by the SPICE library.