Propeller states in locally super-critical ULXs by M. Middleton et al. on Monday 28 November

An expected signature of the presence of neutron stars in the population of

ultraluminous X-ray sources (ULXs) are large scale changes in X-ray luminosity,

as systems reach spin equilibrium and a propeller state ensues. We explore the

predicted luminosity changes when the disc is locally super-critical, finding

that a significant parameter space in dipole field strength and accretion rate

(at large radius) can be accompanied by changes of less than an order of

magnitude in luminosity. We discuss the spectral signature and locate three

ULXs (IC 342 X-1, Cir ULX-5 and NGC 1313 X-1) which appear to show changes

consistent with super-Eddington systems entering a propeller state, and place

rough constraints on the dipole field strength of NGC 1313 X-1 of $<$ 10$^{10}$

G. This work implies that the most reliable means by which to search for

putative propeller states will be to search for changes in hardness ratio and

at high energies.

arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2211.13758v1