White dwarfs typically have masses in a narrow range centered at about 0.6 solar masses (Msun). Only a few ultra-massive white dwarfs (M>1.2 Msun) are known. Those in binary systems are of particular interest because a small amount of accreted mass could drive them above the Chandrasekhar limit, beyond which they become gravitationally unstable. Using data from the XMM-Newton satellite, we show that the X-ray pulsator RX J0648.0-4418 is a white dwarf with mass > 1.2 Msun, based only on dynamical measurements. This ultra-massive white dwarf in a post-common envelope binary with a hot subdwarf can reach the Chandrasekhar limit, and possibly explode as a Type Ia supernova, when its helium-rich companion will transfer mass at an increased rate through Roche lobe overflow.
@article{arxiv.1003.0997,
title = {An ultra-massive fast-spinning white dwarf in a peculiar binary system},
author = {S. Mereghetti and A. Tiengo and P. Esposito and N. La Palombara and G. L. Israel and L. Stella},
journal= {arXiv preprint arXiv:1003.0997},
year = {2010}
}
Comments
Science article and Supporting Online Material are available at http://www.sciencemag.org/ Submitted 13 May 2009; accepted 23 July 2009