https://doi.org/10.1140/epjc/s10052-014-3248-x
Regular Article - Theoretical Physics
Attempt to explain black hole spin in X-ray binaries by new physics
Department of Physics, Center for Field Theory and Particle Physics, Fudan University, Shanghai, 200433, China
* e-mail: bambi@fudan.edu.cn
Received:
17
November
2014
Accepted:
20
December
2014
Published online:
22
January
2015
It is widely believed that the spin of black holes in X-ray binaries is mainly natal. A significant spin-up from accretion is not possible. If the secondary has a low mass, the black hole spin cannot change too much even if the black hole swallows the whole stellar companion. If the secondary has a high mass, its lifetime is too short to transfer the necessary amount of matter and spin the black hole up. However, while black holes formed from the collapse of a massive star with solar metallicity are expected to have low birth spin, current spin measurements show that some black holes in X-ray binaries are rotating very rapidly. Here we show that, if these objects are not the Kerr black holes of general relativity, the accretion of a small amount of matter (
2 
) can make them look like very fast-rotating Kerr black holes. Such a possibility is not in contradiction with any observation and it can explain current spin measurements in a very simple way.
© SIF and Springer-Verlag Berlin Heidelberg, 2015
