%0 Generic %1 citeulike:13626571 %A Bours, M. C. P. %A Marsh, T. R. %A Gaensicke, B. T. %A Tauris, T. M. %A Istrate, A. G. %A Badenes, C. %A Dhillon, V. S. %A Gal-Yam, A. %A Hermes, J. J. %A Kengkriangkrai, S. %A Kilic, M. %A Koester, D. %A Mullally, F. %A Prasert, N. %A Steeghs, D. %A Thompson, S. E. %A Thorstensen, J. R. %D 2015 %K imported %T A double white dwarf with a paradoxical origin? %U http://arxiv.org/abs/1505.05144 %X 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 = 13030 +/- 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 Msun. 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 about 1 Gyr, while that of the primary low-mass white dwarf is likely to be much longer, possibly larger than 5 Gyrs, 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.

@misc{citeulike:13626571, 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 = 13030 +/- 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 Msun. 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 about 1 Gyr, while that of the primary low-mass white dwarf is likely to be much longer, possibly larger than 5 Gyrs, 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.}}, added-at = {2019-03-25T08:20:55.000+0100}, archiveprefix = {arXiv}, author = {Bours, M. C. P. and Marsh, T. R. and Gaensicke, B. T. and Tauris, T. M. and Istrate, A. G. and Badenes, C. and Dhillon, V. S. and Gal-Yam, A. and Hermes, J. J. and Kengkriangkrai, S. and Kilic, M. and Koester, D. and Mullally, F. and Prasert, N. and Steeghs, D. and Thompson, S. E. and Thorstensen, J. R.}, biburl = {https://www.bibsonomy.org/bibtex/26d9e2d7ec1c2ca6d77e571ee650e6476/ericblackman}, citeulike-article-id = {13626571}, citeulike-linkout-0 = {http://arxiv.org/abs/1505.05144}, citeulike-linkout-1 = {http://arxiv.org/pdf/1505.05144}, day = 19, eprint = {1505.05144}, interhash = {5ab3ba1f61d5b835c7c22f29ee9f20fd}, intrahash = {6d9e2d7ec1c2ca6d77e571ee650e6476}, keywords = {imported}, month = may, posted-at = {2015-05-25 03:21:14}, priority = {2}, timestamp = {2019-03-25T08:20:55.000+0100}, title = {{A double white dwarf with a paradoxical origin?}}, url = {http://arxiv.org/abs/1505.05144}, year = 2015 }