University of Leicester
Browse
staa930.pdf (522.82 kB)

Pulsing and non-pulsing ULXs: the iceberg emerges

Download (522.82 kB)
Version 2 2020-05-14, 14:31
Version 1 2020-05-14, 14:30
journal contribution
posted on 2020-05-14, 14:31 authored by Andrew King, Jean-Pierre Lasota
We show that ultraluminous X-ray sources (ULXs) with coherent X-ray pulsing (PULXs) probably have neutron-star spin axes significantly misaligned from their central accretion discs. Scattering in the funnels collimating their emission and producing their apparent super-Eddington luminosities is the most likely origin of the observed correlation between pulse fraction and X-ray photon energy. Pulsing is suppressed in systems with the neutron-star spin closely aligned to the inner disc, explaining why some ULXs show cyclotron features indicating strong magnetic fields, but do not pulse. We suggest that alignment (or conceivably, field suppression through accretion) generally occurs within a fairly short fraction of the ULX lifetime, so that most neutron-star ULXs become unpulsed. As a result we further suggest that almost all ULXs actually have neutron-star accretors, rather than black holes or white dwarfs, reflecting their progenitor high-mass X-ray binary and supersoft X-ray source populations.

Funding

ARK gratefully acknowledges support from the Institut d’Astrophysique de Paris. JPL thanks the Nella and Leon Benoziyo Center for Astrophysics of the Weizmann Institute for hospitality and its members, in particular Boaz Katz, for stimulating discussions. This research was supported by the Polish NCN grant No. 2015/19/B/ST9/01099. JPL acknowledges support from the French Space Agency CNES.

History

Citation

Monthly Notices of the Royal Astronomical Society, Volume 494, Issue 3, May 2020, Pages 3611–3615, https://doi.org/10.1093/mnras/staa930

Version

  • VoR (Version of Record)

Published in

Monthly Notices of the Royal Astronomical Society

Volume

494

Issue

3

Pagination

3611 - 3615

Publisher

Oxford University Press (OUP), Royal Astronomical Society

issn

0035-8711

eissn

1365-2966

Acceptance date

2020-03-28

Copyright date

2020

Available date

2020-04-08

Publisher version

https://academic.oup.com/mnras/article/494/3/3611/5817850

Language

en

Usage metrics

    University of Leicester Publications

    Categories

    Exports

    RefWorks
    BibTeX
    Ref. manager
    Endnote
    DataCite
    NLM
    DC