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Simulating the X-ray luminosity of Be X-ray binaries: the case for black holes versus neutron stars

Simulating the X-ray luminosity of Be X-ray binaries: the case for black holes versus neutron stars
Simulating the X-ray luminosity of Be X-ray binaries: the case for black holes versus neutron stars
There are over 100 Be stars that are known to have neutron star companions but only one such system with a black hole. Previous theoretical work suggests this is not due to their formation but due to differences in X-ray luminosity. It has also been proposed that the truncation of the Be star's circumstellar disc is dependent on the mass of the compact object. Hence, Be star discs in black hole binaries are smaller. Since accretion onto the compact object from the Be star's disc is what powers the X-ray luminosity, a smaller disc in black hole systems leads to a lower luminosity. In this paper, simulations are performed with a range of eccentricities and compact object mass. The disc's size and density are shown to be dependent on both quantities. Mass capture and, in turn, X-ray luminosity are heavily dependent on the size and density of the disc. Be/black hole binaries are expected to be up to ~10 times fainter than Be/neutron star binaries when both systems have the same eccentricity and can be 100 times fainter when comparing systems with different eccentricity.
0035-8711
4810-4816
Brown, Rory O.
84b6cf9e-29e6-4390-a843-5d8f51551910
Ho, Wynn C. G.
d78d4c52-8f92-4846-876f-e04a8f803a45
Coe, Malcolm J.
04dfb23b-1456-46a3-9242-5cee983471d5
Okazaki, Atsuo T.
e6fbd972-98b2-4e4e-ab98-5afb82e799da
Brown, Rory O.
84b6cf9e-29e6-4390-a843-5d8f51551910
Ho, Wynn C. G.
d78d4c52-8f92-4846-876f-e04a8f803a45
Coe, Malcolm J.
04dfb23b-1456-46a3-9242-5cee983471d5
Okazaki, Atsuo T.
e6fbd972-98b2-4e4e-ab98-5afb82e799da

Brown, Rory O., Ho, Wynn C. G., Coe, Malcolm J. and Okazaki, Atsuo T. (2018) Simulating the X-ray luminosity of Be X-ray binaries: the case for black holes versus neutron stars. Monthly Notices of the Royal Astronomical Society, 477 (4), 4810-4816. (doi:10.1093/mnras/sty973).

Record type: Article

Abstract

There are over 100 Be stars that are known to have neutron star companions but only one such system with a black hole. Previous theoretical work suggests this is not due to their formation but due to differences in X-ray luminosity. It has also been proposed that the truncation of the Be star's circumstellar disc is dependent on the mass of the compact object. Hence, Be star discs in black hole binaries are smaller. Since accretion onto the compact object from the Be star's disc is what powers the X-ray luminosity, a smaller disc in black hole systems leads to a lower luminosity. In this paper, simulations are performed with a range of eccentricities and compact object mass. The disc's size and density are shown to be dependent on both quantities. Mass capture and, in turn, X-ray luminosity are heavily dependent on the size and density of the disc. Be/black hole binaries are expected to be up to ~10 times fainter than Be/neutron star binaries when both systems have the same eccentricity and can be 100 times fainter when comparing systems with different eccentricity.

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1804.05749 - Accepted Manuscript
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Accepted/In Press date: 15 April 2018
e-pub ahead of print date: 21 April 2018

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Local EPrints ID: 419835
URI: http://eprints.soton.ac.uk/id/eprint/419835
ISSN: 0035-8711
PURE UUID: 6df6f6ae-51f7-4481-9c7e-79722a3e7b1c
ORCID for Wynn C. G. Ho: ORCID iD orcid.org/0000-0002-6089-6836
ORCID for Malcolm J. Coe: ORCID iD orcid.org/0000-0002-0763-8547

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Date deposited: 23 Apr 2018 16:30
Last modified: 27 Jan 2020 13:43

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