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Ultramassive, Fast-Spinning White Dwarf in a Peculiar Binary System

White dwarfs typically have masses in a narrow range centered at about 0.6 solar mass (M[middle dot in circle]). Only a few ultramassive white dwarfs (mass > 1.2 M[middle dot in circle]) are known. Those in binary systems are of particular interest, because a small amount of accreted mass could d...

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Bibliographic Details
Published in:Science (American Association for the Advancement of Science) 2009-09, Vol.325 (5945), p.1222-1223
Main Authors: Mereghetti, S, Tiengo, A, Esposito, P, La Palombara, N, Israel, G.L, Stella, L
Format: Article
Language:English
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Summary:White dwarfs typically have masses in a narrow range centered at about 0.6 solar mass (M[middle dot in circle]). Only a few ultramassive white dwarfs (mass > 1.2 M[middle dot in circle]) 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 x-ray multimirror mission (XMM)-Newton satellite, we show that the x-ray pulsator RX J0648.0-4418 is a white dwarf with mass > 1.2 M[middle dot in circle], based on dynamical measurements only. This ultramassive 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.
ISSN:0036-8075
1095-9203
DOI:10.1126/science.1176252