Ultraluminous X-ray sources are beamed

Monthly Notices of the Royal Astronomical Society, vol. 526, pp. 2506–2509

Abstract

ABSTRACT We show that magnetar models for ultraluminous X-ray sources (ULXs) have serious internal inconsistencies. The magnetic fields required to increase the limiting luminosity for radiation pressure above the observed (assumed isotropic) luminosities are completely incompatible with the spin-up rates observed for pulsing ULXs. We note that at least one normal Be-star + neutron star system, with a standard (non-magnetar) field, is observed to become a ULX during a large outburst and return to its previous Be-star binary state afterwards. We note further that recent polarimetric observations of the well-studied binary Cyg X-3 reveal that it produces strong emission directed away from the observer, in line with theoretical predictions of its total accretion luminosity from evolutionary arguments. We conclude that the most likely explanation for ULX behaviour involves radiation beaming by accretion disc winds. A large fraction of X-ray binaries must pass through a ULX state in the course of their evolution.

Authors 2

1. J. P. Lasota corresponding

   Centre National de la Recherche Scientifique · Institut d'Astrophysique de Paris · Sorbonne Université · Polish Academy of Sciences · Nicolaus Copernicus Astronomical Center

   Affiliation as printed

   Institut d’Astrophysique de Paris, CNRS et Sorbonne Université , UMR 7095, 98bis Bd Arago, F-75014 Paris , France

   Nicolaus Copernicus Astronomical Center, Polish Academy of Sciences , ul. Bartycka 18, 00-716 Warsaw , Poland

2. Andrew R. King Aachen Leiden Observatory

   Leiden University · University of Amsterdam · University of Leicester · Leiden Observatory

   Affiliation as printed

   Astronomical Institute Anton Pannekoek, University of Amsterdam , Science Park 904, NL-1098 XH Amsterdam , Netherlands

   Astrophysics Group, School of Physics & Astronomy, University of Leicester , Leicester LE1 7RH , UK

   Leiden Observatory, Leiden University , Niels Bohrweg 2, NL-2333 CA Leiden , Netherlands

   Astronomical Institute Anton Pannekoek, University of Amsterdam, Science Park 904, NL-1098 XH Amsterdam, Netherlands