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Beyond Accretion Limits: The Rise of Pulsating Gems

Wolter, Anna; Pintore, Fabio; Esposito, Paolo +23 more

The discovery of several ultraluminous X-ray sources exhibiting fast and rapidly evolving X-ray pulsations unequivocally associates these sources with accreting neutron stars orbiting relatively massive companion stars (> 8M$$ {}_{\odot } $$). Among these ULXs, the brightest pulsating ULX (PULX), NGC 5907 ULX-1, displays a peak luminosity (~2 ×…

XMM-Newton Observations of the Peculiar Be X-Ray Binary A0538-66

Mereghetti, Sandro; Rigoselli, Michela; Ducci, Lorenzo +1 more

A0538-66 is a neutron star/Be x-ray binary located in the Large Magellanic Cloud and, since its discovery in the 70s, it showed a peculiar behavior that makes it a unique object in the high-mass x-ray binaries scene: the extremely eccentric orbit ($$ e=0.72 $$), the short spin period of the neutron star ($$ P=69 $$ ms), the episodes of super-Eddin…

Modeling the Emission and Polarization Properties of Pulsating Ultraluminous X-Ray Sources

Israel, G. L.; Turolla, R.; Pintore, F. +4 more

Pulsating Ultraluminous X-ray Sources (PULXs) are a class of extragalactic sources with high X-ray luminosity, in excess of $$ {10}^{39} $$ erg $$ {\mathrm{s}}^{-1} $$, and showing pulsations that associate them with neutron stars accreting at a super-Eddington rate. A simplified model is presented, which describes the thermal emission from an acc…

Editor's Note: The X-Ray Mysteries of Neutron Stars and White Dwarfs

Schartel, Norbert

The Surprising Long-Term Evolution of the ULXP NGC 7793 P13

Fürst, Felix; Walton, Dominic J.; Brightman, Murray +2 more

The ultra-luminous x-ray pulsar (ULXP) NGC 7793 P13 has been regularly monitored with XMM-Newton, NuSTAR, and Swift for the last 8 years. Here, we present the latest results of this monitoring campaign with respect to the pulse period evolution and spectral variability. We find that since the source recovered from an x-ray low state in 2020–2022 t…