# No magnetars in ULXs

## TL;DR

This paper analyzes pulsing ultraluminous X-ray sources and concludes that their properties are consistent with neutron stars having typical magnetic fields, not magnetars, and that magnetars are unlikely to be present in ULXs.

## Contribution

It demonstrates that observed ULX properties align with standard neutron star magnetic fields, challenging the magnetar hypothesis for ULXs.

## Key findings

- ULX properties match neutron stars with typical magnetic fields
- Magnetar-strength fields are inconsistent with observed ULX data
- Magnetars are unlikely to be part of ULX systems

## Abstract

We consider the current observed ensemble of pulsing ultraluminous X-ray sources (PULXs). We show that all of their observed properties (luminosity, spin period, and spinup rate) are consistent with emission from magnetic neutron stars with fields in the usual range $10^{11} - 10^{13}\, {\rm G}$, which is collimated (`beamed') by the outflow from an accretion disc supplied with mass at a super-Eddington rate, but ejecting the excess, in the way familiar for other (non-pulsing) ULXs. The observed properties are inconsistent with magnetar-strength fields in all cases. We point out that all proposed pictures of magnetar formation suggest that they are unlikely to be members of binary systems, in agreement with the observation that all confirmed magnetars are single. The presence of magnetars in ULXs is therefore improbable, in line with our conclusions above.