TNO (84922) 2003 VS2 light curve

We also carried out photometric observations to derive the rotational light curve amplitude and rotational phase of 2003 VS2 during the stellar occultation. Combining the results and assuming a triaxial shape, we derived the 3D shape of 2003 VS2. Out of the 39 observatories involved in the observational campaign, 12 sites, located in Bulgaria (one), Romania (ten), and Serbia (one), reported a positive detection; this makes it one of the best observed stellar occultations by a TNO so far.

Considering the rotational phase of 2003 VS2 during the stellar occultation and the rotational light curve amplitude derived (Delta_m_=0.264+/- 0.017mag), we obtained a mean area-equivalent diameter of 545+/-13km and a geometric albedo of 0.134+/-0.010. By combining the rotational light curve information with the stellar occultation results, we derived the best triaxial shape for 2003 VS2, which has semiaxes a = 339 +- 5 km, b=235+/-6km, and c=226+/-8km.

The derived aspect angle of 2003 VS2 is theta=59+/-2deg or its supplementary theta=121+/-2deg, depending on the north-pole position of the TNO. The spherical-volume equivalent diameter is 524+/-7km. If we consider large albedo patches on its surface, the semi-major axis of the ellipsoid could be ~ 10 km smaller.

These results are compatible with the previous ones determined from the single-chord 2013 and four-chord 2014 stellar occultations and with the effective diameter and albedo derived from Herschel and Spitzer data. They provide evidence that 2003 VS2's 3D shape is not compatible with a homogeneous triaxial body in hydrostatic equilibrium, but it might be a differentiated body and/or might be sustaining some stress. No secondary features related to rings or material orbiting around 2003 VS2 were detected.