PHA contact-binary (85990) 1999 JV6 light curves

We combine our data with published optical photometry to develop a robust physical model. We determine that the rotation pole resides at negative latitudes in an area with a 5{deg} radius, close to the south ecliptic pole. The refined sidereal rotation period is 6.536787+/-0.000007h.

The radar images are best reproduced with a bilobed shape model. Both lobes of 1999 JV6 can be represented as oblate ellipsoids with a smaller, more spherical component resting at the end of a larger, more elongated component. While contact binaries appear to be abundant in the near-Earth population, there exists just a few published shape models for asteroids in this particular configuration.

By combining the radar-derived shape model with optical light curves we determine a constant-period solution that fits all available data well. Using light curve data alone we determine an upper limit for YORP 8.5x10^-8^rad/day^2^. The bifurcated shape of 1999 JV6 might be a result of two ellipsoidal components gently merging with each other, or a deformation of a rubble pile with a weak-tensile-strength core due to spin-up.

The physical model of 1999 JV6 presented here will enable future studies of contact binary asteroid formation and evolution.