Discovery of the orbital period in the supergiant fast X-ray transient IGR J17544-2619

TL;DR

This paper reports the discovery of a 4.926-day orbital period in the supergiant fast X-ray transient IGR J17544-2619 through analysis of INTEGRAL data, revealing insights into its outburst behavior and stellar parameters.

Contribution

The study identifies the orbital period of IGR J17544-2619 and constrains the supergiant's radius, providing new understanding of SFXT dynamics.

Findings

Orbital period of 4.926 days identified.

Large outbursts occur outside periastron.

Upper limit for supergiant radius <23 solar radii.

Abstract

The supergiant fast X-ray transient (SFXT) system IGR J17544-2619 has displayed many large outbursts in the past and is considered an archetypal example of SFXTs. A search of the INTEGRAL/ISGRI data archive from MJD 52698-54354 has revealed 11 outbursts and timing analysis of the light curve identifies a period of 4.926$\pm$0.001 days which we interpret as the orbital period of the system. We find that large outbursts occasionally occur outside of periastron and place an upper limit for the radius of the supergiant of <23R$_{\sun}$.