Context. The hard X-ray survey that Swift Burst Alert Telescope (BAT) has been performing since late 2004 provides a considerable database for a large number of sources, whose hard X-ray emission are poorly known. Aims: We exploit the BAT survey archive to improve the temporal and spectral characterization of the Galactic hard-X-ray sources. We focus here on the study of the high mass X-ray binary AX J1820.5-1434. Methods: All the data relevant to AX J1820.5-1434 were extracted from the BAT survey archive and analyzed using a folding technique to search for periodical modulations. A broad-band spectral analysis was also performed, complementing the BAT spectrum with the available Swift X-Ray Telescope (XRT) and XMM-Newton pointed observations. Results: A timing analysis revealed the detection of a coherent signal at P0 = 54.0 ± 0.4 d, which we interpret as the orbital period of the binary system. When folded with a period of P0, the light curve shows an asymmetric profile with a minimum roughly consistent with zero intensity. The broadband spectral analysis coupling Swift-XRT, XMM-Newton, and Swift-BAT spectra confirms that the source emission is well modeled with a strongly absorbed power law with no evidence of a high energy exponential cutoff.
The 54-day orbital period of AX J1820.5-1434 unveiled by Swift
D'AI', ANTONINO;
2013-01-01
Abstract
Context. The hard X-ray survey that Swift Burst Alert Telescope (BAT) has been performing since late 2004 provides a considerable database for a large number of sources, whose hard X-ray emission are poorly known. Aims: We exploit the BAT survey archive to improve the temporal and spectral characterization of the Galactic hard-X-ray sources. We focus here on the study of the high mass X-ray binary AX J1820.5-1434. Methods: All the data relevant to AX J1820.5-1434 were extracted from the BAT survey archive and analyzed using a folding technique to search for periodical modulations. A broad-band spectral analysis was also performed, complementing the BAT spectrum with the available Swift X-Ray Telescope (XRT) and XMM-Newton pointed observations. Results: A timing analysis revealed the detection of a coherent signal at P0 = 54.0 ± 0.4 d, which we interpret as the orbital period of the binary system. When folded with a period of P0, the light curve shows an asymmetric profile with a minimum roughly consistent with zero intensity. The broadband spectral analysis coupling Swift-XRT, XMM-Newton, and Swift-BAT spectra confirms that the source emission is well modeled with a strongly absorbed power law with no evidence of a high energy exponential cutoff.
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