中国科学院云南天文台机构知识库

Pulsating ultraluminous X-ray sources (PULXs) are accreting pulsars with apparent X-ray luminosity exceeding 10(39) erg s(-1). We perform Monte Carlo simulations to investigate whether a high collimation effect (or strong beaming effect) is dominant in the presence of accretion outflows, for the fan beam emission of the accretion column of the neutron stars in PULXs. We show that the three nearby PULXs (RX J0209.6-7427, Swift J0243.6+6124, and SMC X-3), namely, the Three Musketeers here, have their main pulsed emission not strongly collimated even if strong outflows exist. This conclusion can be extended to the current sample of extragalactic PULXs, if accretion outflows are commonly produced from them. This means that the observed high luminosity of PULXs is indeed intrinsic, which can be used to infer the existence of very strong surface magnetic fields of similar to 10(13-14) G, possibly multipole fields. However, if strong outflows are launched from the accretion disks in PULXs as a consequence of disk spherization by radiation pressure, regular dipole magnetic fields of similar to 10(12) G may be required, comparable to that of the Three Musketeers, which have experienced large luminosity changes from well below their Eddington limit (2 x 10(38) erg s(-1) for an NS) to super-Eddington and whose maximum luminosity fills the luminosity gap between Galactic pulsars and extragalactic PULXs.