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A double white dwarf with a paradoxical origin?
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Bours, Madelon C. P., Marsh, T. R., Gänsicke, B. T. (Boris T.), Tauris, T. M., Istrate, A. G., Badenes, C., Dhillon, V. S., Gal-Yam, A., Hermes, J. J., Kengkriangkrai, S., Kilic, M., Koester, Detlev, Mullally, F., Prasert, N., Steeghs, D., Thompson, S. E. and Thorstensen, J. R. (2015) A double white dwarf with a paradoxical origin? Monthly Notices of the Royal Astronomical Society, 450 (4). pp. 3966-3974. doi:10.1093/mnras/stv889
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Official URL: http://dx.doi.org/10.1093/mnras/stv889
Abstract
We present Hubble Space Telescope UV spectra of the 4.6-h-period double white dwarf SDSS J125733.63+542850.5. Combined with Sloan Digital Sky Survey optical data, these reveal that the massive white dwarf (secondary) has an effective temperature T2 = 13 030 ± 70 ± 150 K and a surface gravity log g2 = 8.73 ± 0.05 ± 0.05 (statistical and systematic uncertainties, respectively), leading to a mass of M2 = 1.06 M⊙. The temperature of the extremely low-mass white dwarf (primary) is substantially lower at T1 = 6400 ± 37 ± 50 K, while its surface gravity is poorly constrained by the data. The relative flux contribution of the two white dwarfs across the spectrum provides a radius ratio of R1/R2 ≃ 4.2, which, together with evolutionary models, allows us to calculate the cooling ages. The secondary massive white dwarf has a cooling age of ∼1 Gyr, while that of the primary low-mass white dwarf is likely to be much longer, possibly ≳5 Gyr, depending on its mass and the strength of chemical diffusion. These results unexpectedly suggest that the low-mass white dwarf formed long before the massive white dwarf, a puzzling discovery which poses a paradox for binary evolution.
| Item Type: | Journal Article | ||||||||
|---|---|---|---|---|---|---|---|---|---|
| Divisions: | Faculty of Science > Physics | ||||||||
| Journal or Publication Title: | Monthly Notices of the Royal Astronomical Society | ||||||||
| Publisher: | Oxford University Press | ||||||||
| ISSN: | 0035-8711 | ||||||||
| Official Date: | 11 July 2015 | ||||||||
| Dates: |
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| Volume: | 450 | ||||||||
| Number: | 4 | ||||||||
| Page Range: | pp. 3966-3974 | ||||||||
| DOI: | 10.1093/mnras/stv889 | ||||||||
| Status: | Peer Reviewed | ||||||||
| Publication Status: | Published | ||||||||
| Access rights to Published version: | Restricted or Subscription Access |
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