Volume 558, October 2013
|Number of page(s)||5|
|Section||Stellar structure and evolution|
|Published online||10 October 2013|
The 54-day orbital period of AX J1820.5–1434 unveiled by Swift
INAF - Istituto di Astrofisica Spaziale e Fisica Cosmica di Palermo, via U.
La Malfa 153,
2 Dipartimento di Fisica e Chimica, Università di Palermo, via Archirafi 36, 90123 Palermo, Italy
3 INAF – Istituto di Astrofisica Spaziale e Fisica Cosmica di Bologna, via Gobetti 101, 40129 Bologna, Italy
4 INAF – Brera Astronomical Observatory, via Bianchi 46, 23807 Merate ( LC), Italy
Accepted: 11 August 2013
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.
Key words: X-rays: binaries / X-rays: individuals: AX J1820.5-1434 / stars: neutron
© ESO, 2013
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