A strange dwarf scenario for the formation of the peculiar double white dwarf binary SDSS J125733.63+542850.5

作者：Jiang, Long^*; Chen, Wen-Cong^*; Li, Xiang-Dong^*

来源：Monthly Notices of the Royal Astronomical Society, 2018, 476(1): 109-113.

DOI：10.1093/mnras/sty238

• binaries: close
• stars: evolution
• stars: individual: SDSS J125733.63+542850.5
• white dwarfs

The Hubble Space Telescope observation of the double white dwarf (WD) binary SDSS J125733.63+542850.5 reveals that the massive WD has a surface gravity log g(1) similar to 8.7 (which implies a mass of M-1 similar to 1.06 M-circle dot) and an effective temperature T-1 similar to 13 000 K, while the effective temperature of the low-mass WD (M-2 < 0.24 M-circle dot) is T-2 similar to 6400K. Therefore, the massive and the low-mass WDs have a cooling age tau(1) similar to 1 Gyr and tau(2) >= 5 Gyr, respectively. This is in contradiction with traditional binary evolution theory. In this paper, we propose a strange dwarf (SD) scenario to explain the formation of this double WD binary. We assume that the massive WD is a SD originating from a phase transition (PT) in a similar to 1.1 M-circle dot WD, which has experienced accretion and spin-down processes. Its high effective temperature could arise from the heating process during the PT. Our simulations suggest that the progenitor of SDSS J125733.63+542850.5 can be a binary system consisting of a 0.65 M-circle dot WD and a 1.5M(circle dot) main-sequence star in a 1.492 d orbit. Especially, the secondary star (i.e. the progenitor of the low-mass WD) is likely to have an ultra-low metallicity of Z = 0.0001.

• 出版日期2018-5
• 单位南京大学; 商丘师范学院