Volume 573, January 2015
|Number of page(s)||7|
|Published online||16 December 2014|
Displacement of X-ray binaries: constraints on the natal kicks
School of Science, Xi’an Jiaotong University,
710049 Xi’an, PR
2 Key laboratory of Modern Astronomy and Astrophysics (Nanjing University), Ministry of Education, 210093 Nanjing, PR China
Received: 15 July 2014
Accepted: 22 October 2014
Context. This work uses the measured luminosity vs. displacement (LX vs. R) distribution of high-mass X-ray binaries (HMXBs) to constrain the dispersion of kick velocity σkick, which is an important parameter affecting the system velocity of a binary, and hence its spatial offset from the point of origin.
Aims. The aim is to constrain the natal kicks and discriminate between models by comparing the observed LX vs. R distributions with the theoretical simulations.
Methods. Using an up-to-date evolutionary population synthesis technique, the spatial offsets of HMXBs are modeled for a range of theoretical models describing the natal kicks, including different choices of the dispersion of kick velocity σkick, as well as different theoretical treatments for black hole (BH) natal kicks.
Results. The study shows that the value of σkick for neutron stars (NSs) is constrained to be greater than ~100 km s-1, while σkick on the order of several tens of km s-1 may be excluded, though a low or absent natal kick for electron capture supernovae NSs is permitted. In particular, BH natal kicks are found not indispensable to account for the LX vs. R distributions. It is more interesting that full BH natal kicks (i.e., similar to those that NSs may receive) are likely to be ruled out in this study, which is in contrast with the recent finding to explain the observed distribution of low-mass X-ray binaries hosting BHs.
Key words: stars: evolution / X-rays: binaries / X-rays: galaxies: clusters / X-rays: general / galaxies: starburst / binaries: general
© ESO, 2014
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