While working with the Adeona and Gefion asteroid families we were interested in finding objects with D > 15 km and apparent ejection velocities larger than 100 m/s.   We were looking for relatively "large" asteroids because those bodies could not be moved on time-scales comparable with the ages of these families (~500 Myr) by the Yarkovsky force, and we wanted to find objects with an apparent ejection velocity larger than 100 m/s because this seems to be the largest possible velocity produced for such bodies by hydrocode simulations (Michel et al. 2001).   To compute the ejection velocities we computed the center of the family as the center of mass of the family in a, e, and i for all objects with H < 12.5 (which roughly corresponds to D = 10 km), to avoid taking into account objects displaced by the Yarkovsky force.

We found 16 such bodies in the Adeona family and 14 in the Gefion family.  Of these, only 3 had a known spectral type in the Adeona family (Ch), and 11 in the Gefion family (S).   Since these objects cannot have been moved by the Yarkovsky force, the 14 objects with compatible spectral types are possible candidates to have experienced past close encounters with (1) Ceres or other massive asteroids.    We still do not know if the remaining 16 objects are actual members or possible interlopers.   We believe it would be interesting to check their spectral type, in the following table we report their numbers, effective diameteres,
the computed ejection velocities, and the spectral type, when available.
 
 
 

ADEONA FAMILY

GEFION FAMILY

Asteroid number Diameter Ejection Velocity Spectral type   [km] [m/s]           2333 20 125   4157 20 105 Ch 3445 19 110   46644 19 145   997 18 135 Ch 1994 18 165   19133 17 350   5270 17 105   5831 17 320   17284 17 110   22053 16 210   13856 16 250   36648 16 110   4523 15 125 Ch 15445 15 125

Asteroid number Diameter Ejection Velocity Spectral type   [km] [m/s]           3724 22 180   2386 20 110 S 2521 20 140 S 2053 19 145 S 2905 19 115 S 1433 17 200 S 3860 17 185 S 2157 17 105 S 3910 17 100 S 2595 17 185   4417 17 305 S 10064 16 355   1839 16 155 S 2875 15 185 S

The following figures display the locations in the e-a and i-a planes of the centers of the families (black cross), the family members (blue dots) and the asteroids with a possible past history of close encounters (red crosses).
 

Adeona family	Gefion family