Refining the Physical Properties of Brown Dwarf Gliese 229B

Physical Properties of Gliese 229B Based on Newly Determined Carbon and Oxygen Abundances of Gliese 229A

Authors:

Nakajima et al

Abstract:

Recently Tsuji & Nakajima (2914) and Tsuji, Nakajima & Takeda (2015) have developed a method of molecular line spectroscopy of M dwarfs with which Carbon and oxygen abundances are derived respectively from CO and H2O lines in the K band. They applied this method to Gl229A, the primary star of the brown dwarf companion, Gl229B. The derived abundances of Gl229A are logAc=-3.27+/-0.07 and logAo=-3.10+/-0.02, which are close to the classical values of the solar abundances of carbon and oxygen. We generate model spectra of Gl229B for the metallicity of Gl229A as well as for the classical solar metallicity. We find that the differences of the resulting spectra are not so large for the differences of the metallicity of 0.1 dex or so, but we now discuss the spectrum of Gl229B on the basis of the reliable metallicity. From the literature, the lower limit to the age of Gl229A is found to be 0.3Gyr. From the kinematics of Gl229A, we evaluate the upper limit to the age of Gl229A to be 3.0Gyr. The observed and model spectra are compared and goodness of fit is obtained in the range of model parameters, 750

Exploring the Internal Structure of Brown Dwarfs With State Equations for Hydrogen and Helium

Ab initio equations of state for hydrogen (H-REOS.3) and helium (He-REOS.3) and their implications for the interior of Brown Dwarfs

Authors:

Becker et al

Abstract:

We present new equations of state (EOS) for hydrogen and helium covering a wide range of temperatures from 60 K to 107 K and densities from 10−10 g/cm3 to 103 g/cm3. They include an extended set of ab initio EOS data for the strongly correlated quantum regime with an accurate connection to data derived from other approaches for the neighboring regions. We compare linear-mixing isotherms based on our EOS tables with available real-mixture data. A first important astrophysical application of this new EOS data is the calculation of interior models for Jupiter and the comparison with recent results. Secondly, mass-radius relations are calculated for Brown Dwarfs which we compare with predictions derived from the widely used EOS of Saumon, Chabrier and van Horn. Furthermore, we calculate interior models for typical Brown Dwarfs with different masses, namely Corot-3b, Gliese-229b and Corot-15b, and the Giant Planet KOI-889b. The predictions for the central pressures and densities differ by up to 10% dependent on the EOS used. Our EOS tables are made available in the supplemental material of this paper.

Gliese 229B: The First Methane Brown Dwarf

Companions of Stars: From Other Stars to Brown Dwarfs to Planets: The Discovery of the First Methane Brown Dwarf

Author:

Oppenheimer

Abstract:

The discovery of the first methane brown dwarf provides a framework for describing the important advances in both fundamental physics and astrophysics that are due to the study of companions of stars. I present a few highlights of the history of this subject along with details of the discovery of the brown dwarf Gliese 229B. The nature of companions of stars is discussed with an attempt to avoid biases induced by anthropocentric nomenclature. With the newer types of remote reconnaissance of nearby stars and their systems of companions, an exciting and perhaps even more profound set of contributions to science is within reach in the near future. This includes an exploration of the diversity of planets in the universe and perhaps soon the first solid evidence for biological activity outside our Solar System.