Gänsicke, BT;
Koester, D;
Farihi, J;
Toloza, O;
(2018)
Broadening of Ly α by neutral helium in DBA white dwarfs.
Monthly Notices of the Royal Astronomical Society
, 481
(4)
pp. 4323-4331.
10.1093/mnras/sty2526.
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Abstract
Traces of photospheric hydrogen are detected in at least half of all white dwarfs with heliumdominated atmospheres through the presence of Hα in high-quality optical spectroscopy. Previous studies have noted significant discrepancies between the hydrogen abundances derived from Hα and Ly α for a number of stars where ultraviolet spectroscopy is also available. We demonstrate that this discrepancy is caused by inadequate treatment of the broadening of Ly α by neutral helium. When fitting Hubble Space Telescope far-ultraviolet spectroscopy of 17 DB white dwarfs using our new line profile calculations, we find good agreement between log (NH/NHe) measured from Ly α and Hα. Larger values of log (NH/NHe) based on Ly α are still found for three stars, which are among the most distant in our sample, and we show that a small amount of interstellar absorption from neutral hydrogen can account for this discrepancy.
| Type: | Article |
|---|---|
| Title: | Broadening of Ly α by neutral helium in DBA white dwarfs |
| Open access status: | An open access version is available from UCL Discovery |
| DOI: | 10.1093/mnras/sty2526 |
| Publisher version: | http://dx.doi.org/10.1093/mnras/sty2526 |
| Language: | English |
| Additional information: | © 2018 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society. This version is the version of record. For information on re-use, please refer to the publisher’s terms and conditions. |
| Keywords: | line: profiles, stars: atmospheres, white dwarfs, ultraviolet: stars |
| UCL classification: | UCL 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/10059679 |
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