Pulsating ULXs: large pulsed fraction excludes strong beaming
Poutanen Juri; Tsygankov Sergey S; Zwart Simon Portegies; Mushtukov Alexander A; Nagirner Dmitrij I
Pulsating ULXs: large pulsed fraction excludes strong beaming
Poutanen Juri
Tsygankov Sergey S
Zwart Simon Portegies
Mushtukov Alexander A
Nagirner Dmitrij I
OXFORD UNIV PRESS
Julkaisun pysyvä osoite on:
https://urn.fi/URN:NBN:fi-fe2021042827372
https://urn.fi/URN:NBN:fi-fe2021042827372
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.
Kokoelmat
- Rinnakkaistallenteet [19207]