1203.0773 (P. Pastor)
P. Pastor
The acceleration of a spherical dust particle caused by an interstellar gas flow depends on a drag coefficient which is for the given particle and flow of interstellar gas certain function of the relative speed of the dust particle with respect to the interstellar gas. We investigate motion of the dust particle in the case when the acceleration caused by the interstellar gas flow (with the variability of the drag coefficient taken into account) represent a small perturbation to the gravity of a central star. We present the secular time derivatives of the Keplerian orbital elements of the dust particle under the action of the acceleration from the interstellar gas flow, with the linear variability of the drag coefficient taken into account, for arbitrary orbit orientation. The semimajor axis of the dust particle is a decreasing function of time for the acceleration with constant drag coefficient and also for the acceleration with variable drag coefficient. Decrease of the semimajor axis is slower for the acceleration with variable drag coefficient. Minimal and maximal values of the semimajor axis decrease are determined. In the planar case, when the velocity of hydrogen gas lies in the orbital plane of the particle, the orbit always approaches the position with the maximal value of the transversal component of the hydrogen gas velocity vector measured in the perihelion. Properties of the orbital evolution derived from the secular time derivatives are consistent with numerical integrations of equation of motion. If the interstellar gas flow speed is much larger than the speed of the dust particle, then the linear approximation of dependence of the drag coefficient on the relative speed of the dust particle with respect to the interstellar gas is usable for practically arbitrary values of the molecular speed ratios (Mach numbers).
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http://arxiv.org/abs/1203.0773
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