The trans-Neptunian object (84922) 2003 VS2 through stellar occultations
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 November 7th, 2014, 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 three-dimensional shape of the body, with principal semi-axes a = 313.8 7.1 km, b = 265.5+8.8-9.8 km, and c = 247.3+26.6-43.6 km, which is not consistent with a Jacobi triaxial equilibrium figure. The derived spherical volume equivalent diameter of 548.3 +29.5-44.6 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 +0.015-0.014) and, under the assumption that the object is a Maclaurin spheroid, the density = 1400+1000-300 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.