2007AJ....133.1903B

Perryman and collaborators found that for the Hyades cluster the fraction of multiple stars increases from G stars to early-A stars. We discuss here whether this may be a general property of star formation or whether collisions in the cluster environment change the fractions of binary stars. A star ring of mainly F and G stars is seen around the Hyades cluster core, supposedly created by a shock wave due to a supernova explosion. These ring stars show the same fraction of binary stars as observed for the F and G stars in the core of the cluster. This suggests that collisions in the high stellar density cluster center did not measurably change the multiple-star fractions. There is so far only evidence of this one supernova explosion in the Hyades. If this is indeed the only one, then only one massive star was born in the cluster. There are also fewer than 10 white dwarf descendants of B stars found in the cluster. Unless many white dwarfs and neutron stars evaporated from the cluster, the initial mass function for stellar masses >2 M_☉ must have been very steep, corresponding to a Salpeter function with an exponent of less than -3.3.