Candidate stellar occultations by Centaurs and trans-Neptunian objects up to 2014^{⋆,⋆⋆,⋆⋆⋆,⋆⋆⋆⋆}

¹ Observatório Nacional/MCTI, R. General José Cristino 77, CEP 20921-400 Rio de Janeiro, RJ, Brazil
e-mail: camargo@linea.gov.br
² Observatório do Valongo/UFRJ, Ladeira do Pedro Antônio 43, CEP 20080-090 Rio de Janeiro, RJ, Brazil
e-mail: massaf@astro.ufrj.br
³ Observatoire de Paris-Meudon/LESIA, 5 place Jules Janssen, 92195 Meudon, France
⁴ Université Pierre et Marie Curie, Institut Universitaire de France, Paris, France
e-mail: bruno.sicardy@obspm.fr

Received: 31 August 2013
Accepted: 29 October 2013

Abstract

Context. We study trans-Neptunian objects (TNOs) from stellar occultations.

Aims. We predict stellar occultations from 2012.5 to the end of 2014 by 5 Centaurs and 34 TNOs.

Methods. These predictions were achieved in two ways: first, we built catalogues with precise astrometric positions of the stellar content around the paths on the sky of these targets, as seen by a ground-based observer; second, the observed positions of the targets were determined with the help of these same catalogues so that we could improve their ephemerides and the reliability of the predictions. The reference system is the International Celestial Reference System (ICRS) as realised by the Fourth US Naval Observatory CCD Astrograph Catalog (UCAC4). All the sky paths as well as the selected targets were observed from Oct. 2011 to May 2013 with the ESO/MPG 2.2 m telescope equipped with the Wide Field Imager (WFI). All astrometric results were obtained with the platform for reduction of astronomical images automatically (PRAIA) after correcting the images for overscan, bias, and flatfield.

Results. The catalogues with the stellar content around the sky path of each selected target are complete down to magnitude R = 19 and have an average positional accuracy of about 50 milliarcseconds. This same average accuracy also holds for the observed positions of the targets. In the catalogues from the sky paths, stellar proper motions for non-UCAC4 objects were derived from the combination of the current epoch WFI observations with either the 2MASS or the USNO-B1 catalogues. The offsets between the observed and (JPL) ephemeris positions of the targets frequently reach absolute values of some hundreds of milliarcseconds.

Conclusions. We present here stellar occultation predictions for the selected 5 Centaurs and 34 TNOs from 2012.5 to the end of 2014. This work is also an extension of two previous prediction works by us, the first one for Pluto, Charon, Nix, and Hydra, and the second for ten other large TNOs. The use of catalogues from the observations of the sky paths in the astrometry of the TNOs and Centaurs enhanced the coherence between their positions and those of the respective occulted candidate stars. New observations of these TNOs and Centaurs are continuously used to redetermine their ephemerides.