Non-Vestoid candidate asteroids in the inner main belt

Abstract

Most Howardite-Eucrite-Diogenite (HED) meteorites (analogs to V-type asteroids) are thought to originate from asteroid (4) Vesta. However, some HEDs show distinct oxygen isotope ratios and therefore are thought to originate from other asteroids. In this study, we try to identify asteroids that may represent parent bodies of those mismatching HEDs. In particular, the origin of the anomalous Bunburra Rockhole meteorite was traced back to the inner main asteroid belt, showing that there might be asteroids that are not genetically linked to the asteroid (4) Vesta (the main source of V-type asteroids and HED meteorites) in the inner main belt. In this work we identify V-type asteroids outside the dynamical Vesta family whose rotational properties (retrograde vs prograde rotation) suggest the direction of Yarkovsky drift that sets them apart from typical Vestoids and Vesta fugitives. Specifically Nesvorny et al. 2008 simulated escapes paths from the Vesta family and showed that typical Vesta fugitives in the inner main asteroid belt at semi-major axis a < 2.3 AU have to have retrograde rotations and physical and thermal parameters that maximize the Yarkovsky force in order to evolve to scattered orbits within 1-2 Gyrs (age of the Vesta collisional family). Therefore large asteroids outside the Vesta family and with a < 2.3 AU and having thermal and rotational properties minimizing the Yarkovsky drift or showing Yarkovsky drift direction towards (4) Vesta are the best candidates for non-Vestoids V-type asteroids and therefore parent bodies of anomalous HED. In this study, we have performed accurate photometric observations and determined sense of rotation for several asteroids testing their links to Vesta and anomalous HED. We have found several potential non-Vestoid candidates. Those objects have to be studied in more detail to fully confirm their link to anomalous HEDs.