On the orbital evolution of dust grains in the sublimation region around WD1145+017

Abstract

We investigate the orbital evolution of dust grains in the sublimation region near thewhite dwarf WD 1145+017. The selection of basalt as the main constituent of transient material around WD1145+017 is dictated by observations of the boundary of the dust-free zone near the Sun for zodiacal dust cloud and by the orbital evolution of dust grains of different composition. The rate of sublimation is set by the temperature of dust grains, depending on their size, distance to the host star, and characteristics of the composition material. We consider the influence of radiation pressure and the Poynting-Robertson drag on the dynamics of the dust grains. The boundaries of sublimation zone near WD1145+017 for grains with the size range of 0.01 to 100 μm are in the range from 56 to 1000 stellar radius (R∗). When calculating the orbital evolution, we assumed that the grain leaves the parent body at a distance much greater than the radius of sublimation. We also estimate the lifetime of dust grains of different sizes and composition starting their orbital motion from a distance of 90 R∗, corresponding to the main orbital period of the transit material. The lifetime of grains, considering their orbital evolution is about an order of magnitude less than that obtained from the heat balance alone. Sub-micron grains at a distance of 90 R∗ evaporate almost instantly. Basalt grains with a radius larger than 20 μm can survive for more than a year. The estimated dust accretion rate is 3.2 × 109 g s-1