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Title: On the spin period distribution in Be/X-ray binaries

Abstract

There is a remarkable correlation between the spin periods of the accreting neutron stars (NSs) in Be/X-ray binaries (BeXBs) and their orbital periods. Recently, Knigge et al. showed that the distribution of the spin periods contains two distinct subpopulations peaked at ∼10 s and ∼200 s, respectively, and suggested that they may be related to two types of supernovae for the formation of the NSs, i.e., core-collapse and electron-capture supernovae. Here we propose that the bimodal spin period distribution is likely to be ascribed to different accretion modes of the NSs in BeXBs. When the NS tends to capture material from the warped, outer part of the Be star disk and experiences giant outbursts, a radiatively cooling dominated disk is formed around the NS, which spins up the NS and is responsible for the short-period subpopulation. In BeXBs that are dominated by normal outbursts or are persistent, the accretion flow is advection-dominated or quasi-spherical. The spin-up process is accordingly inefficient, leading to longer periods of the neuron stars. The potential relation between the subpopulations and the supernova mechanism is also discussed.

Authors:
;
Publication Date:
OSTI Identifier:
22356938
Resource Type:
Journal Article
Journal Name:
Astrophysical Journal
Additional Journal Information:
Journal Volume: 786; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0004-637X
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; BINARY STARS; CORRELATIONS; DISTRIBUTION; ELECTRON CAPTURE; NEUTRON STARS; NEUTRONS; RADIATIVE COOLING; SPHERICAL CONFIGURATION; SPIN; STAR ACCRETION; SUPERNOVAE; X RADIATION

Citation Formats

Cheng, Z. -Q., Shao, Y., and Li, X.-D., E-mail: lixd@nju.edu.cn. On the spin period distribution in Be/X-ray binaries. United States: N. p., 2014. Web. doi:10.1088/0004-637X/786/2/128.
Cheng, Z. -Q., Shao, Y., & Li, X.-D., E-mail: lixd@nju.edu.cn. On the spin period distribution in Be/X-ray binaries. United States. https://doi.org/10.1088/0004-637X/786/2/128
Cheng, Z. -Q., Shao, Y., and Li, X.-D., E-mail: lixd@nju.edu.cn. 2014. "On the spin period distribution in Be/X-ray binaries". United States. https://doi.org/10.1088/0004-637X/786/2/128.
@article{osti_22356938,
title = {On the spin period distribution in Be/X-ray binaries},
author = {Cheng, Z. -Q. and Shao, Y. and Li, X.-D., E-mail: lixd@nju.edu.cn},
abstractNote = {There is a remarkable correlation between the spin periods of the accreting neutron stars (NSs) in Be/X-ray binaries (BeXBs) and their orbital periods. Recently, Knigge et al. showed that the distribution of the spin periods contains two distinct subpopulations peaked at ∼10 s and ∼200 s, respectively, and suggested that they may be related to two types of supernovae for the formation of the NSs, i.e., core-collapse and electron-capture supernovae. Here we propose that the bimodal spin period distribution is likely to be ascribed to different accretion modes of the NSs in BeXBs. When the NS tends to capture material from the warped, outer part of the Be star disk and experiences giant outbursts, a radiatively cooling dominated disk is formed around the NS, which spins up the NS and is responsible for the short-period subpopulation. In BeXBs that are dominated by normal outbursts or are persistent, the accretion flow is advection-dominated or quasi-spherical. The spin-up process is accordingly inefficient, leading to longer periods of the neuron stars. The potential relation between the subpopulations and the supernova mechanism is also discussed.},
doi = {10.1088/0004-637X/786/2/128},
url = {https://www.osti.gov/biblio/22356938}, journal = {Astrophysical Journal},
issn = {0004-637X},
number = 2,
volume = 786,
place = {United States},
year = {Sat May 10 00:00:00 EDT 2014},
month = {Sat May 10 00:00:00 EDT 2014}
}