Bours, M.C.P., Marsh, T.R., Gaensicke, B.T. et al. (14 more authors) (2015) A double white dwarf with a paradoxical origin? Monthly Notices of the Royal Astronomical Society, 450 (4). pp. 3966-3974. ISSN 0035-8711
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.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2015 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved. |
Keywords: | binaries: close; stars: individual: SDSS J125733.63+542850.5; white dwarfs |
Dates: |
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Institution: | The University of Sheffield |
Academic Units: | The University of Sheffield > Faculty of Science (Sheffield) > Department of Physics and Astronomy (Sheffield) |
Funding Information: | Funder Grant number SCIENCE AND TECHNOLOGY FACILITIES COUNCIL ST/J001589/1 SCIENCE AND TECHNOLOGY FACILITIES COUNCIL ST/M001350/1 |
Depositing User: | Symplectic Sheffield |
Date Deposited: | 26 Oct 2017 15:11 |
Last Modified: | 26 Oct 2017 15:11 |
Published Version: | https://doi.org/10.1093/mnras/stv889 |
Status: | Published |
Publisher: | Oxford University Press |
Refereed: | Yes |
Identification Number: | 10.1093/mnras/stv889 |
Related URLs: | |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:122718 |