TY - JOUR
T1 - Supergiant Fast X-ray Transients in outburst
T2 - New Swift observations of XTE J1739-302, IGR J17544-2619 and IGR J08408-4503
AU - Sidoli, L.
AU - Romano, P.
AU - Ducci, L.
AU - Paizis, A.
AU - Cusumano, G.
AU - Mangano, V.
AU - Krimm, H. A.
AU - Vercellone, S.
AU - Burrows, D. N.
AU - Kennea, J. A.
AU - Gehrels, N.
PY - 2009/8
Y1 - 2009/8
N2 - We report on new X-ray outbursts observed with Swift from three Supergiant Fast X-ray Transients (SFXTs): XTE J1739-302, IGR J17544-2619 and IGR J08408-4503. XTE J1739-302 underwent a new outburst on 2008 August 13, IGR J17544-2619 on 2008 September 4 and IGR J08408-4503 on 2008 September 21. While the XTE J1739-302 and IGR J08408-4503 bright emission triggered the Swift/Burst Alert Telescope, IGR J17544-2619 did not, thus we could perform a spectral investigation only of the spectrum below 10 keV. The broad-band spectra from XTE J1739-302 and IGR J08408-4503 were compatible with the X-ray spectral shape displayed during the previous flares. A variable absorbing column density during the flare was observed in XTE J1739-302 for the first time. The broad-band spectrum of IGR J08408-4503 requires the presence of two distinct photon populations, a cold one (∼0.3 keV) most likely from a thermal halo around the neutron star and a hotter one (1.4-1.8 keV) from the accreting column. The outburst from XTE J1739-302 could be monitored with a very good sampling, thus revealing a shape which can be explained with a second wind component in this SFXT, in analogy to what we have suggested in the periodic SFXT IGR J11215-5952. The outburst recurrence time-scale in IGR J17544-2619 during our monitoring campaign with Swift suggests a long orbital period of ∼150 d (in a highly eccentric orbit), compatible with what previously observed with INTEGRAL.
AB - We report on new X-ray outbursts observed with Swift from three Supergiant Fast X-ray Transients (SFXTs): XTE J1739-302, IGR J17544-2619 and IGR J08408-4503. XTE J1739-302 underwent a new outburst on 2008 August 13, IGR J17544-2619 on 2008 September 4 and IGR J08408-4503 on 2008 September 21. While the XTE J1739-302 and IGR J08408-4503 bright emission triggered the Swift/Burst Alert Telescope, IGR J17544-2619 did not, thus we could perform a spectral investigation only of the spectrum below 10 keV. The broad-band spectra from XTE J1739-302 and IGR J08408-4503 were compatible with the X-ray spectral shape displayed during the previous flares. A variable absorbing column density during the flare was observed in XTE J1739-302 for the first time. The broad-band spectrum of IGR J08408-4503 requires the presence of two distinct photon populations, a cold one (∼0.3 keV) most likely from a thermal halo around the neutron star and a hotter one (1.4-1.8 keV) from the accreting column. The outburst from XTE J1739-302 could be monitored with a very good sampling, thus revealing a shape which can be explained with a second wind component in this SFXT, in analogy to what we have suggested in the periodic SFXT IGR J11215-5952. The outburst recurrence time-scale in IGR J17544-2619 during our monitoring campaign with Swift suggests a long orbital period of ∼150 d (in a highly eccentric orbit), compatible with what previously observed with INTEGRAL.
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U2 - 10.1111/j.1365-2966.2009.15049.x
DO - 10.1111/j.1365-2966.2009.15049.x
M3 - Article
AN - SCOPUS:68149123411
SN - 0035-8711
VL - 397
SP - 1528
EP - 1538
JO - Monthly Notices of the Royal Astronomical Society
JF - Monthly Notices of the Royal Astronomical Society
IS - 3
ER -