Cooling Delays from Iron Sedimentation and Iron Inner Cores in White Dwarfs

Autor:	Caplan, M. E., Freeman, I. F., Horowitz, C. J., Cumming, A., Bellinger, E. P.
Rok vydání:	2021
Předmět:	Astrophysics - Solar and Stellar Astrophysics Condensed Matter - Other Condensed Matter
Druh dokumentu:	Working Paper
DOI:	10.3847/2041-8213/ac1f99
Popis:	Do white dwarfs have inner cores made of iron? Neutron rich nuclei like $^{56}$Fe experience a net gravitational force and sediment toward the core. Using new phase diagrams and molecular dynamics simulations, we show that $^{56}$Fe should separate into mesoscopic Fe-rich crystallites due to its large charge relative to the background. At solar abundances, these crystallites rapidly precipitate and form an inner core of order 100 km and $10^{-3} M_\odot$ that may be detectable with asteroseismology. Associated cooling delays could be up to a Gyr for low mass white dwarfs but are only $\sim$0.1 Gyr for massive white dwarfs, so while this mechanism may contribute to the Q-branch the heating is insufficient to fully explain it. Comment: 8 pages, 5 figures, accepted for publication in ApJ Letters
Databáze:	arXiv
Externí odkaz:	http://arxiv.org/abs/2108.11389 Zobrazit plný text záznamu View this record from Arxiv