A double white dwarf with a paradoxical origin?
A double white dwarf with a paradoxical origin?
复制标题
起源自相矛盾的双白矮星？
DOI：
10.1093/mnras/stv889
复制
发表时间：
2015
影响因子：
4.8
通讯作者：
Bours M
中科院分区：
文献类型：
--
作者：
Bours M
本文给出了4.6 h周期双白色矮星SDSS J125733.63+542850.5的紫外光谱。结合Sloan数字巡天光学数据，这些数据表明，大质量白色矮星（次级）的有效温度T2 = 13030 ± 70 ± 150 K，表面重力记录2 = 8.73 ± 0.05 ± 0.05（分别为统计和系统不确定性），导致质量M2 = 1.06 M。质量极低的白色矮星（主矮星）的温度在T1 = 6400 ± 37 ± 50 K时要低得多，而它的表面重力受数据的约束很差。两颗白色矮星在整个光谱中的相对通量贡献提供了R1/R2 4.2的半径比，这与进化模型一起使我们能够计算冷却年龄。次级大质量白色矮星的冷却年龄为101 Gyr，而初级小质量白色矮星的冷却年龄可能更长，可能为105 Gyr，这取决于它的质量和化学扩散的强度。这些结果出乎意料地表明，低质量的白色矮星早在大质量的白色矮星形成之前很久就形成了，这是一个令人困惑的发现，为双星演化提出了一个悖论。
We presentHubble Space TelescopeUV 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 temperatureT2= 13 030 ± 70 ± 150 K and a surface gravity logg2= 8.73 ± 0.05 ± 0.05 (statistical and systematic uncertainties, respectively), leading to a mass ofM2= 1.06 M⊙. The temperature of the extremely low-mass white dwarf (primary) is substantially lower atT1= 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 ofR1/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.