Asteroid spin-states of 4 Gyr-old family

However, there is growing evidence that some of the real families are larger than the corresponding cluster of objects in orbital elements, as well as there are families that escaped identification from clustering methods. An alternative method has been developed in order to identify collisional families from the correlation between the asteroid fragment sizes and their proper semimajor axis distance from the family center (V-shape).

This method has been shown to be effective in the cases of the very diffuse families that formed Gyrs ago. Here we use multiple technique observations of asteroids to provide corroborating evidence that one of those groups of asteroids identified as a family from the correlation between size and proper semimajor axis of asteroids are real fragments of a common parent body and, thus form a collisional family. We obtained photometric observations of asteroids in order to construct their rotational lightcurves, we combine these with literature lightcurves and sparse-in-time photometry, we input these data in the so-called lightcurve inversion methods, which allow us to determine a convex approximation to the 3D shape of the asteroids and their orientation in space; from the latter we extract the latitude (or obliquity) of the spin pole in order to assess whether an object is prograde or retrograde.