The Trans-Neptunian Object (84922) 2003 VS2 through Stellar Occultations
Bérard, D.; Brosch, N.; Maury, A.; Cacella, P.; Alvarez-Candal, A.; Jehin, E.; Opitom, C.; Sicardy, B.; Ortiz, J. L.; Desmars, J.; Lecacheux, J.; Santos-Sanz, P.; Morales, N.; Duffard, R.; Fernández-Valenzuela, E.; Braga-Ribas, F.; Assafin, M.; Camargo, J. I. B.; Vieira-Martins, R.; Rommel, F. L.; Pratt, A.; Behrend, R.; Moindrot, S.; Peyrot, A.; Morgado, B.; Kaspi, S.; Ivanov, V. D.; Machado, D. I.; Sfair, R.; Emilio, M.; Vachier, F.; Bianco, F. B.; Spagnotto, J.; Gomes-Junior, A. R.; Gil-Hutton, R.; Manulis, I.; Benedetti-Rossi, Gustavo; Colas, A. F.; Almenares, L.; Artola, R.; Baum, T. -P.; Ceretta, A.; Colazo, C. A.; Melia, R.; Pollock, J.; Roland, S.; Tancredi, G.; Teng, J. -P.; Feys, F.; Jacques, C.; Malacarne, M.; Milone, A. C.; Rojas, G.
Brazil, France, Spain, United States, Uruguay, Argentina, Switzerland, Israel, Germany, Belgium, Chile
Abstract
We present results from three world-wide campaigns that resulted in the detections of two single-chord and one multi-chord stellar occultations by the plutino object (84922) 2003 VS2. From the single-chord occultations in 2013 and 2014 we obtained accurate astrometric positions for the object, while from the multi-chord occultation on 2014 November 7, we obtained the parameters of the best-fitting ellipse to the limb of the body at the time of occultation. We also obtained short-term photometry data for the body in order to derive its rotational phase during the occultation. The rotational light curve present a peak-to-peak amplitude of 0.141 ± 0.009 mag. This allows us to reconstruct the 3D shape of the body, with principal semi-axes of a = 313.8 ± 7.1 km, b={265.5}-9.8+8.8 km, and c={247.3}-43.6+26.6 km, which is not consistent with a Jacobi triaxial equilibrium figure. The derived spherical volume equivalent diameter of {548.3}-44.6+29.5 km is about 5% larger than the radiometric diameter of 2003 VS2 derived from Herschel data of 523 ± 35 km, but still compatible with it within error bars. From those results we can also derive the geometric albedo ({0.123}-0.014+0.015) and, under the assumption that the object is a Maclaurin spheroid, the density ρ ={1400}-300+1000 for the plutino. The disappearances and reappearances of the star during the occultations do not show any compelling evidence for a global atmosphere considering a pressure upper limit of about 1 microbar for a pure nitrogen atmosphere, nor secondary features (e.g., rings or satellite) around the main body.