Evidence of rocky planetesimals orbiting two Hyades stars

Abstract

The Hyades is the nearest open cluster, relatively young and containing numerous A-type stars; its known age, distance, and metallicity make it an ideal site to study planetary systems around 2-3Mȯ stars at an epoch similar to the late heavy bombardment. Hubble Space Telescope farultraviolet spectroscopy strongly suggests ongoing, external metal pollution in two remnant Hyads. For ongoing accretion in both stars, the polluting material has log [n(Si)/n(C)] > 0.2, is more carbon deficient than chondritic meteorites and is thus rocky. These data are consistent with a picture where rocky planetesimals and small planets have formed in the Hyades around two main-sequence A-type stars, whose white dwarf descendants bear the scars. These detections via metal pollution are shown to be equivalent to infrared excesses of LIR/L* ̃ 10-6 in the terrestrial zone of the stars. © 2013 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.