* Astronomy

Title: Modelling the light-curve of KIC012557548: an extrasolar planet with a comet like tail
Authors: Jan Budaj

An object with a very peculiar light-curve was discovered recently using Kepler data from first two quarters. Authors argue that this object may be a transiting disintegrating planet with a comet like dusty tail. The aim of the present paper is to verify the model suggested by the discoverers by the light-curve modelling and put constraints on the geometry of the dust region and various dust properties. We modify the code Shellspec designed for modelling of the interacting binaries to calculate the light-curves of stars with planets with comet like tails. We take into account the Mie absorption and scattering on spherical dust grains of various sizes assuming realistic dust opacities and phase functions and finite radius of the source of light (star). The light-curve is reanalysed using first six quarters of the Kepler data. We prove that the peculiar light-curve of this objects is in agreement with the idea of a planet with a comet like tail. Light-curve has a prominent pre-transit brightening and a less prominent brightening after the transit. Both are caused by the forward scattering and are a strong function of the particle size. Dust density in the tail is a steep decreasing function of angle (distance) from the planet which indicates significant dust destruction along the tail caused by the star. The particle size of the grains in the tail is about 0.1 micron but can be slightly larger if data with the shorter exposure (short cadence) were available. The orbital period of the planet was slightly improved. This light-curve with pre-transit brightening is analogous to the light-curve of epsilon Aur with mid-eclipse brightening and forward scattering plays significant role in both of them.

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