Swift/X-ray Telescope monitoring of the candidate supergiant fast X-ray transient IGR J16418-4532

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 (∼3.7 d and ∼1250 s, respectively). Our observations, for a total of ∼43 ks, 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 ∼5 × 10[superscript: 16] to 10[superscript: 21] g. Our data suggest, based on the X-ray behaviour, that this is an intermediate SFXT.