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Kunming, China

Gao Z.F.,Urumqi Observatory | Gao Z.F.,University of Chinese Academy of Sciences | Gao Z.F.,Nanjing University | Wang N.,Urumqi Observatory | And 4 more authors.
Astrophysics and Space Science | Year: 2011

In this paper, we consider the effect of Landau levels on the decay of superhigh magnetic fields of magnetars. Applying 3P2 anisotropic neutron superfluid theory yield a second-order differential equation for a superhigh magnetic field B and its evolutionary timescale t. The superhigh magnetic fields may evolve on timescales ~(106-107) yrs for common magnetars. According to our model, the activity of a magnetar may originate from instability caused by the high electron Fermi energy. © 2011 Springer Science+Business Media B.V. Source

Zhang X.,Yunnan Observatory | Zhang X.,College Hill | Chen X.,Yunnan Observatory | Han Z.,Yunnan Observatory
Astrophysics and Space Science | Year: 2010

Mass is a fundamental parameter, but the masses are not well known for most hot subdwarfs. We propose a method of determining the masses of hot subdwarfs. Using this method, we studied the masses of hot subdwarfs from the ESO supernova Ia progenitor survey and the Hamburg quasar survey. The study shows that most of the subdwarf B stars have masses between 0.42 and 0.54 M⊙, whilst most sdO stars are in the range 0.40~0. 55 M⊙. Comparing our study to the theoretical mass distributions of Han et al. (Mon. Not. R. Astron. Soc. 341:669, 2003), we found that sdO stars with mass less than ~0. 5 M⊙ may evolve from sdB stars, whilst most high-mass (>0. 5 M⊙) sdO stars result from mergers directly. © 2010 Springer Science+Business Media B.V. Source

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