Observational constraints on late heavy bombardment episodes around young solar analogs

Thermal emission from dust is investigated around 36 nearby G and K stars s elected as analogs to the young Sun during the period of late heavy bombard ment on the Moon(prior to 3.8 Ga). Measurements or upper limits at 12, 25, and 60 mu m wavelengths were obtained from observations by the Infrared Ast ronomical Satellite (IRAS), and photosphere contributions were subtracted u sing the models of Kurucz and ground-based optical and near-infrared data. A single star, HD 128400, has circumstellar emission that is consistent wit h a 490 K blackbody with an effective area similar to 7 x 10(3) times that of the present solar system zodiacal cloud. Emission from 260 K dust at a m ean level exceeding 900 times the present zodiacal cloud can be ruled out f or the remaining 35 stars. A model of dust production by cometary impacters scaled to the lunar cratering record shows that dust from late heavy bomba rdment episodes around these stars would fall below IRAS detection levels a fter 500 Myr (4.1 Ga). The emission from HD 128400 is broadly consistent wi th the model at the star's 300 Myr age.