Research output: Contribution to journal › Article › peer-review
Pulsating ULXs: Large pulsed fraction excludes strong beaming. / Mushtukov, Alexander A.; Portegies Zwart, Simon; Tsygankov, Sergey S.; Nagirner, Dmitrij I.; Poutanen, Juri.
In: Monthly Notices of the Royal Astronomical Society, Vol. 501, No. 2, 01.02.2021, p. 2424-2429.Research output: Contribution to journal › Article › peer-review
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TY - JOUR
T1 - Pulsating ULXs: Large pulsed fraction excludes strong beaming
AU - Mushtukov, Alexander A.
AU - Portegies Zwart, Simon
AU - Tsygankov, Sergey S.
AU - Nagirner, Dmitrij I.
AU - Poutanen, Juri
N1 - Funding Information: This work was supported by The Dutch Research Council (NWO) Veni Fellowship (AAM) and the grant 14.W03.31.0021 of the Ministry of Science and Higher Education of the Russian Federation. We are grateful to Paolo Esposito, Valery Suleimanov, and an anonymous referee for useful comments and discussions. Publisher Copyright: © 2021 The Author(s). Copyright: Copyright 2021 Elsevier B.V., All rights reserved.
PY - 2021/2/1
Y1 - 2021/2/1
N2 - The recent discovery of pulsating ultraluminous X-ray sources (ULXs) shows that the apparent luminosity of accreting neutron stars can exceed the Eddington luminosity by a factor of 100s. The relation between the actual and apparent luminosity is a key ingredient in theoretical models of ULXs, but it is still under debate. A typical feature of the discovered pulsating ULXs is a large pulsed fraction (PF). Using Monte Carlo simulations, we consider a simple geometry of accretion flow and test the possibility of simultaneous presence of a large luminosity amplification due the geometrical beaming and a high PF. We argue that these factors largely exclude each other and only a negligible fraction of strongly beamed ULX pulsars can show PF above 10 per cent. Discrepancy between this conclusion and current observations indicates that pulsating ULXs are not strongly beamed and their apparent luminosity is close to the actual one.
AB - The recent discovery of pulsating ultraluminous X-ray sources (ULXs) shows that the apparent luminosity of accreting neutron stars can exceed the Eddington luminosity by a factor of 100s. The relation between the actual and apparent luminosity is a key ingredient in theoretical models of ULXs, but it is still under debate. A typical feature of the discovered pulsating ULXs is a large pulsed fraction (PF). Using Monte Carlo simulations, we consider a simple geometry of accretion flow and test the possibility of simultaneous presence of a large luminosity amplification due the geometrical beaming and a high PF. We argue that these factors largely exclude each other and only a negligible fraction of strongly beamed ULX pulsars can show PF above 10 per cent. Discrepancy between this conclusion and current observations indicates that pulsating ULXs are not strongly beamed and their apparent luminosity is close to the actual one.
KW - accretion, accretion discs
KW - stars: neutron
KW - stars: oscillations
KW - X-rays: binaries
UR - http://www.scopus.com/inward/record.url?scp=85100299986&partnerID=8YFLogxK
U2 - 10.1093/mnras/staa3809
DO - 10.1093/mnras/staa3809
M3 - Article
AN - SCOPUS:85100299986
VL - 501
SP - 2424
EP - 2429
JO - Monthly Notices of the Royal Astronomical Society
JF - Monthly Notices of the Royal Astronomical Society
SN - 0035-8711
IS - 2
ER -
ID: 74239067