Mon. Not. R. Astron. Soc., 400, 258-262 (2009/November-3)
The first broad-band X-ray study of the supergiant fast X-ray transient SAX J1818.6-1703 in outburst.
SIDOLI L., ROMANO P., ESPOSITO P., LA PAROLA V., KENNEA J.A., KRIMM H.A., CHESTER M.M., BAZZANO A., BURROWS D.N. and GEHRELS N.
Abstract (from CDS):
The Supergiant Fast X-ray Transient (SFXT) SAX J1818.6-1703 underwent an outburst on 2009 May 6 and was observed with Swift. We report on these observations which, for the first time, allow us to study the broad-band spectrum from soft to hard X-rays of this source. No X-ray spectral information was available on this source before the Swift monitoring. The spectrum can be deconvolved well with models usually adopted to describe the emission from HMXB X-ray pulsars, and is characterized by a very high absorption, a flat power law (photon index ∼0.1-0.5) and a cut-off at about 7-12 keV. Alternatively, the SAX J1818.6-1703 emission can be described with a Comptonized emission from a cold and optically thick corona, with an electron temperature kTe= 5-7 keV, a hot seed photon temperature, kT0, of 1.3-1.4 keV and an optical depth for the Comptonizing plasma, τ, of about 10. The 1-100 keV luminosity at the peak of the flare is 3x1036 erg/s (assuming the optical counterpart distance of 2.5 kpc). These properties of SAX J1818.6-1703 resemble those of the prototype of the SFXT class, XTE J1739-302. The monitoring with Swift/XRT reveals an outburst duration of about 5 d, similar to other members of the class of SFXTs, confirming SAX J1818.6-1703 as a member of this class.
© 2009 The Authors. Journal compilation © 2009 RAS
X-rays: binaries - X-rays: individual: SAX J1818.6-1703
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