uu.seUppsala University Publications
Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
The influence of electron collisions on non-LTE Li line formation in stellar atmospheres
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Theoretical Astrophysics.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Theoretical Astrophysics.
2011 (English)In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 529, A31- p.Article in journal (Refereed) Published
Place, publisher, year, edition, pages
EDP Sciences, 2011. Vol. 529, A31- p.
Keyword [en]
atomic data, line: formation, stars: abundances
National Category
Physical Sciences
Identifiers
URN: urn:nbn:se:uu:diva-152922DOI: 10.1051/0004-6361/201016418ISI: 000289557200039OAI: oai:DiVA.org:uu-152922DiVA: diva2:414410
Available from: 2011-05-03 Created: 2011-05-03 Last updated: 2017-12-11
In thesis
1. Atomic Processes in Stellar Atmospheres: Inelastic Collisions and Effects on Late-type Spectra
Open this publication in new window or tab >>Atomic Processes in Stellar Atmospheres: Inelastic Collisions and Effects on Late-type Spectra
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Chemical abundances as measured from stellar spectral lines are often subject to uncertainties due to lack of accurate data for inelastic collisions, which is needed for non-local thermodynamic equilibrium (non-LTE) modelling. For cool stars, understanding of collision processes with electrons and hydrogen atoms is required to achieve high precision measurements. In this thesis, I have investigated the role of these collisions on the non-LTE formation of Li and Mg spectral lines in late-type stars.

In the case of Li, electron impact excitation processes were calculated using the R-matrix with pseudo states method and the results found to agree well with recent calculations using the convergent close-coupling technique. These modern data were employed in non-LTE calculations by updating an existing model atom, which already included modern data for hydrogen collision processes. Our results were compared with calculations using older semi-empirical approximation calculations and only small differences were found: about 0.01 dex (~ 2%) or less in the abundance corrections. We therefore conclude that the influence of uncertainties in the electron collision data on non-LTE calculations is negligible. Indeed, together with the collision data for the charge transfer process Li + H ↔ Li+ + H- now available, and barring the existence of an unknown important collisional process, the collisional data in general is not a source of significant uncertainty in non-LTE Li line formation calculations.

In the case of Mg, electron impact excitation processes were again calculated with the Rmatrix with pseudo states method, and used together with recent hydrogen collision calculations to build and test a model atom, without free parameters, for non-LTE modelling. Both electron and hydrogen collision processes, including charge transfer and excitation, are found to be important thermalising agents in various cases. The modelled spectra agree well with observed spectra from benchmark stars in the optical and infrared. The modelling predicts non-LTE abundance corrections ∆A(Mg)NLTE–LTE in dwarfs, both solar metallicity and metal-poor, to be very small (of order 0.01 dex), even smaller than found in previous studies. In giants, corrections vary greatly between lines, but can be as large as 0.4 dex. Results of calculations in a large grid of 1D model atmospheres are presented, and the implications for studies of Mg discussed. The propagation of uncertainties in the inelastic collision data to those in stellar abundances is investigated, and found to lead to small uncertainties, once again typically less than 0.01 dex (2%), although for few stellar models in specific lines (e.g., metal-poor suns, in the 7691 Å line) uncertainties can be as large as 0.03 dex (7%).

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2015. 87 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1249
Keyword
Spectral line: formation, atomic data, stellar abundances.
National Category
Astronomy, Astrophysics and Cosmology Atom and Molecular Physics and Optics
Research subject
Physics with specialization in Astrophysics
Identifiers
urn:nbn:se:uu:diva-249168 (URN)978-91-554-9240-3 (ISBN)
Public defence
2015-06-03, Polhemssalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 10:00 (English)
Opponent
Supervisors
Available from: 2015-05-13 Created: 2015-04-11 Last updated: 2015-07-07

Open Access in DiVA

No full text

Other links

Publisher's full text

Authority records BETA

Martinez Osorio, Yeisson FabianBarklem, Paul

Search in DiVA

By author/editor
Martinez Osorio, Yeisson FabianBarklem, Paul
By organisation
Theoretical Astrophysics
In the same journal
Astronomy and Astrophysics
Physical Sciences

Search outside of DiVA

GoogleGoogle Scholar

doi
urn-nbn

Altmetric score

doi
urn-nbn
Total: 950 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf