8,273 research outputs found
Age determination of the HR8799 planetary system using asteroseismology
Discovery of the first planetary system by direct imaging around HR8799 has
made the age determination of the host star a very important task. This
determination is the key to derive accurate masses of the planets and to study
the dynamical stability of the system. The age of this star has been estimated
using different procedures. In this work we show that some of these procedures
have problems and large uncertainties, and the real age of this star is still
unknown, needing more observational constraints. Therefore, we have developed a
comprehensive modeling of HR8799, and taking advantage of its gamma
Doradus-type pulsations, we have estimated the age of the star using
asteroseismology. The accuracy in the age determination depends on the rotation
velocity of the star, and therefore an accurate value of the inclination angle
is required to solve the problem. Nevertheless, we find that the age estimate
for this star previously published in the literature ([30,160] Myr) is
unlikely, and a more accurate value might be closer to the Gyr. This
determination has deep implications on the value of the mass of the objects
orbiting HR8799. An age around 1 Gyr implies that these objects are
brown dwarfs.Comment: 5 pages, 3 figures, accepted in MNRAS Letter
Generic ordering of structural transitions in quasi-one-dimensional Wigner crystals
We investigate the dependence of the structural phase transitions in an
infinite quasi-one-dimensional system of repulsively interacting particles on
the profile of the confining channel. Three different functional expressions
for the confinement potential related to real experimental systems are used
that can be tuned continuously from a parabolic to a hard-wall potential in
order to find a thorough understanding of the ordering of the chain-like
structure transitions. We resolve the longstanding issue why the most theories
predicted a 1-2-4-3-4 sequence of chain configurations with increasing density,
while some experiments found the 1-2-3-4 sequence.Comment: 7 pages, 5 figure
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