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arXiv · 1308.6047

Time-dependent nonextensivity arising from the rotational evolution of solar-type stars

Jose R. P. Silva·Mackson M. F. Nepomuceno·Braulio B. Soares·Daniel B. de Freitas
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Abstract

Nonextensive formalism is a generalization of the Boltzmann-Gibbs statistics. In this formalism the entropic index q is a quantity characterizing the degree of nonextensivity, and is interpreted as a parameter of long-memory or long-range interactions between the components of the system. Since its proposition in 1988, this formalism has been applied to investigate a wide variety of natural phenomena. In stellar astrophysics, theoretical distribution function based on nonextensive formalism (q-distributions) has been successfully applied to reproduce the distribution of stellar radial and rotational velocity data. In this paper, we investigate the time variation of the entropic index q obtained from the distribution of rotation, Vsini, for a sample of 254 rotational data for solar-type stars from 11 open clusters aged between 35.5Myr and 2.6Gyr. As a result, we have found an anti-correlation between the entropic index q and the age of clusters, and that the distribution of rotation Vsini for these stars becomes extensive for an age greater than about 170Myr. Assuming that the parameter q is associated with long-memory effects, we suggest that the memory of the initial angular momentum of solar-type stars can be scaled by the entropic index q. We also propose a physical link between the parameter q and the magnetic braking of stellar rotation.

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Jose R. P. Silva, Mackson M. F. Nepomuceno, Braulio B. Soares, Daniel B. de Freitas. 2013-12-09. Time-dependent nonextensivity arising from the rotational evolution of solar-type stars. https://doi.org/10.1088/0004-637x/777/1/20

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