Swift unveils the orbital period of IGR J18214-1318

G. Cusumano, A. D'Aì, A. Segreto, V. La Parola, M. Del Santo

Published 2020-09-14Version 1

We analysed 13 years of the Neil Gehrels Swift Observatory survey data collected on the High Mass X-ray Binary IGR J18214-1318. Performing the timing analysis we detected a periodic signal of 5.42 d. From the companion star characteristics we derived an average orbital separation of $\sim 41 \rm R_{\odot}\simeq 2 R_{\star}$. The spectral type of the companion star (O9) and the tight orbital separation suggest that IGR~J18214-1318 is a wind accreting source with eccentricity lower than 0.17. The intensity profile folded at the orbital period shows a deep minimum compatible with an eclipse of the source by the companion star. In addition, we report on the broad-band 0.6--100 keV spectrum using data from XMM-Newton, NuSTAR, and Swift, applying self-consistent physical models. We find that the spectrum is well fitted either by a pure thermal Comptonization component, or, assuming that the source is a neutron star accreting above the critical regime, by a combined thermal and bulk-motion Comptonization model. In both cases, the presence of a local neutral absorption (possibly related to the thick wind of the companion star) is required.