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- Blackwell-Whitehead, Richard, et al.
(author)
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Infrared Mn I laboratory oscillator strengths for the study of late type stars and ultracool dwarfs
- 2011
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In: Astronomy & Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 525
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Journal article (peer-reviewed)abstract
- Aims. The aim of our new laboratory measurements is to measure accurate absolute oscillator strengths for neutral manganese transitions in the infrared needed for the study of late-type stars and ultracool dwarfs. Methods. Branching fractions have been measured by high resolution Fourier transform spectroscopy and combined with radiative level lifetimes in the literature to yield oscillator strengths. Results. We present experimental oscillator strengths for 20 Mn I transitions in the wavelength range 3216 to 13 997 angstrom, 15 of which are in the infrared. The transitions at 12 899 angstrom and 12 975 angstrom are observed as strong features in the spectra of late-type stars and ultracool dwarfs. We have fitted our calculated spectra to the observed Mn I lines in spectra of late-type stars. Using the new experimentally measured Mn I log(gf) values together with existing data for Mn I hyperfine structure splitting factors we determined the manganese abundance to be log N(Mn) = -6.65 +/- 0.05 in the atmosphere of the Sun, log N(Mn) = 6.95 +/- 0.20 in the atmosphere of Arcturus, and log N(Mn) = -6.70 +/- 0.20 in the atmosphere of M 9.5 dwarf 2MASSW 0140026+270150.
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| 2. |
- Blackwell-Whitehead, R. J., et al.
(author)
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Experimental TiI oscillator strengths and their application to cool star analysis
- 2006
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In: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 1365-2966 .- 0035-8711. ; 373:4, s. 1603-1609
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Journal article (peer-reviewed)abstract
- We report experimental oscillator strengths for 88 Ti I transitions covering the wavelength range 465-3892 nm, 67 of which had no previous experimental values. Radiative lifetimes for 13 energy levels, including the low energy levels 3d(2)(F-3) 4s4p ((3)p) z(5)D(j)degrees have been measured using time-resolved laser-induced fluorescence. Intensity-calibrated Ti I spectra have been measured using Fourier transform spectroscopy to determine branching fractions for the decay channels of these levels. The branching fractions are combined with the radiative lifetimes to yield absolute transition probabilities and oscillator strengths. Our measurements include 50 transitions in the previously unobserved infrared region lambda > 1.0 mu m, a region of particular interest to the analysis of cool stars and brown dwarfs.
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| 3. |
- Jones, HRA, et al.
(author)
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Status of the physics of substellar objects project
- 2005
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In: Astronomical Notes - Astronomische Nachrichten. - : Wiley. - 0004-6337. ; 326:10, s. 920-924
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Journal article (peer-reviewed)abstract
- A full understanding of the properties of substellar objects is one of the major challenges facing astrophysics. Since their discovery in 1995, hundreds of brown dwarfs and extrasolar planets have been discovered. While these discoveries have enabled important comparisons with theory, observational progress has been much more rapid than the theoretical understanding of cool atmospheres. The reliable determination of mass, abundances, gravities and temperatures is not yet possible. The key problem is that substellar objects emit their observable radiation in the infrared region of the spectrum where our knowledge of atomic, molecular and line broadening data is poor. Here we report on the status of our PoSSO (Physics of SubStellar Objects) project. In order to understand brown dwarfs and extrasolar planets increasing more like those in our solar system, we are studying a wide range of processes. Here we give an update on the project and sketch an outline of atoms, molecules and processes requiring study.
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