2 00 7 Medium – separation binaries do not affect the first steps of planet formation

The first steps of planet formation are marked by the growth and crystallization of sub–micrometer–sized dust grains accompanied by dust settling toward the disk midplane. In this paper we explore whether the first steps of planet formation are affected by the presence of medium–separation stellar companions. We selected two large samples of disks around single and binary T Tauri stars in Taurus that are thought to have only a modest age spread of a few Myr. The companions of our binary sample are at projected separations between ∼10 and 450AU with masses down to about 0.1M⊙. We used the strength and shape of the 10μm silicate emission feature as a proxy for grain growth and for crystallization respectively. The degree of dust settling was evaluated from the ratio of fluxes at two different mid–infrared wavelengths. We find no statistically significant difference between the distribution of 10μm silicate emission features from single and binary systems. In addition, the distribution of disk flaring is indistinguishable between the single and binary system samples. These results show that the first steps of planet formation are not affected by the presence of a companion at tens of AU. Subject headings: circumstellar matter – planetary systems: protoplanetary disks –