# On the properties of a newborn magnetar powering the X-ray transient CDF-S XT2

## TL;DR

This paper models the X-ray transient CDF-S XT2 as emission from a newborn magnetar's ultra-relativistic wind, fitting its light curve and spectrum to infer key magnetar properties.

## Contribution

It confirms that the X-ray transient can be explained by magnetic dissipation in a newborn magnetar's wind, providing detailed fits and magnetar parameter estimates.

## Key findings

- The model fits the light curve and spectral evolution of CDF-S XT2.
- Key magnetar properties such as initial spin and magnetic field are constrained.
- The internal magnetic dissipation process explains the observed X-ray emission.

## Abstract

Very recently \citet{XueYQ2019} reported an important detection of the X-ray transient, CDF-S XT2, whose light curve is analogous to X-ray plateau features of gamma-ray burst afterglows. They suggested that this transient is powered by a remnant stable magnetar from a binary neutron star merger since several pieces of evidence (host galaxy, location, and event rate) all point toward such an assumption. In this paper, we revisit this scenario and confirm that this X-ray emission can be well explained by the internal gradual magnetic dissipation process in an ultra-relativistic wind of the newborn magnetar. We show that both the light curve and spectral evolution of CDF-S XT2 can be well fitted by such a model. Furthermore, we can probe some key properties of the central magnetar, such as its initial spin period, surface magnetic field strength and wind saturation Lorentz factor.