Harris, GJ;
Lynas-Gray, AE;
Miller, S;
Tennyson, J;
(2004)
The Effect of the Electron Donor H⁺₃ on the Pre-Main-Sequence and Main-Sequence Evolution of Low-Mass, Zero-Metallicity Stars.
The Astrophysical Journal
, 600
(2)
pp. 1025-1034.
10.1086/380090.
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Abstract
H₃⁺ has been shown (1991 work of Lenzuni and coworkers) to be the dominant positive ion in a zero-metallicity gas at low temperature and intermediate to high density. It therefore affects both the number of free electrons and the opacity of the gas. The most recent H₃⁺ partition function (1995 work of Neale & Tennyson) is an order of magnitude larger at 4000 K than all previous partition functions, implying that H₃⁺ is a more important electron donor than previously thought. Here we present new Rosseland mean opacities for a hydrogen-helium gas of 1000 K ≤ T ≤ 9000 K and -14 ≤ log₁₀ [ρ (g cm⁻³)] ≤ -2. In the calculation of these opacities, we have made use of the latest collision-induced absorption data as well as the most recent H₃⁺ partition function and line opacity data. It is shown that these updated and new sources of opacity give rise to a Rosseland mean opacity for a hydrogen-helium gas that is, in general, greater than that calculated in earlier works. The new opacity data are then used to model the evolution of low-mass (0.15-0.8 M_{☉}), zero-metallicity stars, from pre-main-sequence collapse to main-sequence turnoff. To investigate the effect of H₃⁺ on the evolution of low-mass, zero-metallicity stars, we repeat our calculations neglecting H₃⁺ as a source of electrons and line opacity. We find that H₃⁺ can have an effect on the structure and evolution of stars of mass ~0.5 M_{☉} or less. A gray atmosphere is used for the calculation, which is sufficient to demonstrate that H₃⁺ affects the evolution of very low mass stars to a greater degree than previously believed.
| Type: | Article |
|---|---|
| Title: | The Effect of the Electron Donor H⁺₃ on the Pre-Main-Sequence and Main-Sequence Evolution of Low-Mass, Zero-Metallicity Stars |
| Open access status: | An open access version is available from UCL Discovery |
| DOI: | 10.1086/380090 |
| Publisher version: | https://doi.org/10.1086/380090 |
| Language: | English |
| Additional information: | This version is the version of record. For information on re-use, please refer to the publisher’s terms and conditions. |
| Keywords: | atomic data, stars: evolution, stars: low-mass, brown dwarfs |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Physics and Astronomy |
| URI: | https://discovery.ucl.ac.uk/id/eprint/1302 |
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