Analytic Models of Brown Dwarfs and the Substellar Mass Limit
We present the analytic theory of brown dwarf evolution and the lower mass limit of the hydrogen burning main-sequence stars and introduce some modifications to the existing models. We give an exact expression for the pressure of an ideal nonrelativistic Fermi gas at a finite temperature, therefore...
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| Format: | Article |
| Language: | English |
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Wiley
2016-01-01
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| Series: | Advances in Astronomy |
| Online Access: | http://dx.doi.org/10.1155/2016/5743272 |
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| author | Sayantan Auddy Shantanu Basu S. R. Valluri |
| author_facet | Sayantan Auddy Shantanu Basu S. R. Valluri |
| author_sort | Sayantan Auddy |
| collection | DOAJ |
| description | We present the analytic theory of brown dwarf evolution and the lower mass limit of the hydrogen burning main-sequence stars and introduce some modifications to the existing models. We give an exact expression for the pressure of an ideal nonrelativistic Fermi gas at a finite temperature, therefore allowing for nonzero values of the degeneracy parameter. We review the derivation of surface luminosity using an entropy matching condition and the first-order phase transition between the molecular hydrogen in the outer envelope and the partially ionized hydrogen in the inner region. We also discuss the results of modern simulations of the plasma phase transition, which illustrate the uncertainties in determining its critical temperature. Based on the existing models and with some simple modification, we find the maximum mass for a brown dwarf to be in the range 0.064M⊙–0.087M⊙. An analytic formula for the luminosity evolution allows us to estimate the time period of the nonsteady state (i.e., non-main-sequence) nuclear burning for substellar objects. We also calculate the evolution of very low mass stars. We estimate that ≃11% of stars take longer than 107 yr to reach the main sequence, and ≃5% of stars take longer than 108 yr. |
| format | Article |
| id | doaj-art-b37677992dc541a58018940f7c54b65c |
| institution | Kabale University |
| issn | 1687-7969 1687-7977 |
| language | English |
| publishDate | 2016-01-01 |
| publisher | Wiley |
| record_format | Article |
| series | Advances in Astronomy |
| spelling | doaj-art-b37677992dc541a58018940f7c54b65c2025-02-03T01:31:45ZengWileyAdvances in Astronomy1687-79691687-79772016-01-01201610.1155/2016/57432725743272Analytic Models of Brown Dwarfs and the Substellar Mass LimitSayantan Auddy0Shantanu Basu1S. R. Valluri2Department of Physics and Astronomy, The University of Western Ontario, London, ON, N6A 3K7, CanadaDepartment of Physics and Astronomy, The University of Western Ontario, London, ON, N6A 3K7, CanadaDepartment of Physics and Astronomy, The University of Western Ontario, London, ON, N6A 3K7, CanadaWe present the analytic theory of brown dwarf evolution and the lower mass limit of the hydrogen burning main-sequence stars and introduce some modifications to the existing models. We give an exact expression for the pressure of an ideal nonrelativistic Fermi gas at a finite temperature, therefore allowing for nonzero values of the degeneracy parameter. We review the derivation of surface luminosity using an entropy matching condition and the first-order phase transition between the molecular hydrogen in the outer envelope and the partially ionized hydrogen in the inner region. We also discuss the results of modern simulations of the plasma phase transition, which illustrate the uncertainties in determining its critical temperature. Based on the existing models and with some simple modification, we find the maximum mass for a brown dwarf to be in the range 0.064M⊙–0.087M⊙. An analytic formula for the luminosity evolution allows us to estimate the time period of the nonsteady state (i.e., non-main-sequence) nuclear burning for substellar objects. We also calculate the evolution of very low mass stars. We estimate that ≃11% of stars take longer than 107 yr to reach the main sequence, and ≃5% of stars take longer than 108 yr.http://dx.doi.org/10.1155/2016/5743272 |
| spellingShingle | Sayantan Auddy Shantanu Basu S. R. Valluri Analytic Models of Brown Dwarfs and the Substellar Mass Limit Advances in Astronomy |
| title | Analytic Models of Brown Dwarfs and the Substellar Mass Limit |
| title_full | Analytic Models of Brown Dwarfs and the Substellar Mass Limit |
| title_fullStr | Analytic Models of Brown Dwarfs and the Substellar Mass Limit |
| title_full_unstemmed | Analytic Models of Brown Dwarfs and the Substellar Mass Limit |
| title_short | Analytic Models of Brown Dwarfs and the Substellar Mass Limit |
| title_sort | analytic models of brown dwarfs and the substellar mass limit |
| url | http://dx.doi.org/10.1155/2016/5743272 |
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