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Pulsating ULXs: large pulsed fraction excludes strong beaming




TekijätMushtukov Alexander A, Zwart Simon Portegies, Tsygankov Sergey S, Nagirner Dmitrij I, Poutanen Juri

KustantajaOXFORD UNIV PRESS

Julkaisuvuosi2021

JournalMonthly Notices of the Royal Astronomical Society

Tietokannassa oleva lehden nimiMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY

Lehden akronyymiMON NOT R ASTRON SOC

Vuosikerta501

Numero2

Aloitussivu2424

Lopetussivu2429

Sivujen määrä6

ISSN0035-8711

eISSN1365-2966

DOIhttps://doi.org/10.1093/mnras/staa3809

Rinnakkaistallenteen osoitehttps://research.utu.fi/converis/portal/detail/Publication/53329098


Tiivistelmä
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.

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Last updated on 2024-26-11 at 18:52