2011A&A...529A..30D

A growing number of previously hidden Galactic X-ray sources are now detected with recent surveys performed by the INTEGRAL and Swift satellites. Most of these new sources eluded past surveys due to their large local X-ray extinction and consequent low soft X-ray flux. The Swift-BAT performs daily monitoring of the sky in an energy band (15-150keV) which is only marginally affected by X-ray extinction, thus allowing for the search of long periodicities in the light curve and identification of the nature of the X-ray sources. We performed a period search using the folding technique in the Swift-BAT light curves of three INTEGRAL sources: IGRJ05007-7047, IGRJ13186-6257 and IGRJ17354-3255. Their periodograms show significant peaks at 30.77±0.01d, 19.99±0.01d and 8.448±0.002d, respectively. We estimate the significance of these features from the χ² distribution of all the trials, finding a probability ≤1.5x10^–4 that the detections occurred due to chance. We complement our analysis with the study of their broadband X-ray emission. We identify the periodicities with the orbital periods of the sources. The periods are typical for the wind accretors X-ray binaries and we support this identification showing that also their energy spectra are compatible with an X-ray spectral emission characteristic of high-mass X-ray binaries. The spectrum of IGRJ05007-704 that resides in the Large Magellanic Cloud, does not show any intrinsic local absorption, whereas the spectra of the Galactic sources IGRJ17354-3255 and IGRJ13186-6257 may be affected by a local absorber. The folded light curve for IGRJ13186-6257 suggests a possible Be companion star.