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Peculiar Euphrosyne

Grant number: 14/14212-2
Support type:Regular Research Grants - Publications - Scientific article
Duration: September 01, 2014 - February 28, 2015
Field of knowledge:Physical Sciences and Mathematics - Astronomy - Positional Astronomy and Celestial Mechanics
Principal Investigator:Valerio Carruba
Grantee:Valerio Carruba
Home Institution: Faculdade de Engenharia (FEG). Universidade Estadual Paulista (UNESP). Campus de Guaratinguetá. Guaratinguetá , SP, Brazil


Euphrosyne is the largest body of its namesake family and it contains more then 99% of the family mass. Among large asteroid families, the Euphrosyne group is peculiar because of its quite steep size frequency distribution, significantly depleted in large and medium-sized asteroids (8 < D < 12 km).The current steep size frequency distribution of the Euphrosyne family has been suggested to be the result of a grazing impact in which only the farthest, smallest members failed to accrete. The Euphrosyne family is however also very peculiar because of its dynamics: near its center it is crossed by the nu6 = g-g6 linear secular resonance, and it hosts the largest population (140 bodies) of asteroids in nu6 anti-aligned librating states (or Tina-like asteroids) in the main belt. In this work we investigated the orbital evolution of newly obtained members of the dynamical family, with an emphasis on its interaction with the nu6 resonance. Because of its unique resonant configuration, large and medium sized asteroids tend to migrate away from the family orbital region faster than small-sized objects, that were ejected further away from the family center. As a consequence, the size-frequency distribution of the Euphrosyne family becomes steeper in time, with a growing depletion in the number of the largest family members. We estimate that the current size-frequency distribution could be attained from a typical, initial size-frequency distribution in time-scales of 500 Myr, consistently with estimates of the family age obtained with other, independent, methods. (AU)