Swift/XRT monitoring of the candidate Supergiant Fast X-ray Transient IGR J16418-4532

TL;DR

This study presents comprehensive Swift/XRT observations of the candidate supergiant fast X-ray transient IGR J16418-4532, analyzing its light curve to understand its accretion processes and classify its nature.

Contribution

The paper applies the clumpy wind model to detailed X-ray light curves, providing insights into the accretion mechanism and classifying the source as an intermediate SFXT.

Findings

X-ray emission explained by accretion from a clumpy stellar wind.

Observed clump masses range from ~5E16 g to 1E21 g.

Source classified as an intermediate SFXT.

Abstract

We report on the Swift monitoring of the candidate supergiant fast X-ray transient (SFXT) IGR J16418-4532, for which both orbital and spin periods are known (~3.7d and ~1250s, respectively). Our observations, for a total of ~43ks, span over three orbital periods and represent the most intense and complete sampling of the light curve of this source with a sensitive X-ray instrument. With this unique set of observations we can address the nature of this transient. By applying the clumpy wind model for blue supergiants to the observed X-ray light curve, and assuming a circular orbit, the X-ray emission from this source can be explained in terms of the accretion from a spherically symmetric clumpy wind, composed of clumps with different masses, ranging from ~5E16 g to 1E21g. Our data suggest, based on the X-ray behaviour, that this is an intermediate SFXT.