1996A&A...313..857G

This paper studies the behaviour of star-grazing planetesimal bodies in the neighbourhood of UX Ori-type stars. When approaching a star, large size bodies (diameteres of ten meters or more) disintegrate into a number of small fragments under the effect of thermal stresses. In turn, the fragments sublimate within a sphere of about ten stellar radii and form a circumstellar gas envelope. An important feature of this envelope is a strong excess of heavy elements. Our calculations show that the radiative force on the metal-enriched gas is much larger than in the case of standard chemical composition and exceeds by few times the gravity of the star. As a result, the evaporated matter is accelerated outward and is expelled from the system by radiative pressure. Thus, the evaporation of planetesimals in the vicinity of young stars leads to complex gas motions which include infall, quasi-keplerian rotation and the radial outflow typical of radiatively driven stellar winds.