We report on combined INTEGRAL and XMM-Newton observations of the supergiant fast X-ray transient IGR J16418−4532. The observations targeted the X-ray eclipse region of IGR J16418−4532s orbit with continuous INTEGRAL observations across ∼25% of orbital phase and two quasi-simultaneous XMM-Newton observations of length 20 ks and 14 ks, occurring during, and just after the eclipse respectively. An enhanced INTEGRAL emission history is provided with 19 previously unreported outbursts identified in the archival 18−60 keV data set. The XMM-Newton eclipse observation showed prominent Fe-emission and a flux of 2.8×10 −13 erg cm −2 s −1 (0.5 -10 keV). Through the comparison of the detected eclipse and post eclipse flux, the supergiant mass loss rate through the stellar wind was determined asṀ w = 2.3-3.8×10 −7 M yr −1 . The post eclipse XMM-Newton observation showed a dynamic flux evolution with signatures of the X-ray pulsation, a period of flaring activity, structured n H variations and the first ever detection of an X-ray intensity dip, or 'off-state', in a pulsating supergiant fast X-ray transient. Consideration is given to the origin of the X-ray dip and we conclude that the most applicable of the current theories of X-ray dip generation is that of a transition between Compton cooling dominated and radiative cooling dominated subsonic accretion regimes within the 'quasi-spherical' model of wind accretion. Under this interpretation, which requires additional confirmation, the neutron star in IGR J16418−4532 possesses a magnetic field of ∼10 14 G, providing tentative observational evidence of a highly magnetised neutron star in a supergiant fast X-ray transient for the first time. The implications of these results on the nature of IGR J16418−4532 itself and the wider SFXT class are discussed.

XMM-Newton observations of the supergiant fast X-ray transient IGR J17544−2619 are reported and placed in the context of an analysis of archival INTEGRAL/IBIS data that provides a refined estimate of the orbital period at 4.9272±0.0004 days. A complete outburst history across the INTEGRAL mission is reported. Although the new XMM-Newton observations (each lasting ∼15 ks) targeted the peak flux in the phasefolded hard X-ray light curve of IGR J17544−2619, no bright outbursts were observed, the source spending the majority of the exposure at intermediate luminosities of the order of several 10 33 erg s −1 (0.5 − 10 keV) and displaying only low level flickering activity. For the final portion of the exposure, the luminosity of IGR J17544−2619 dropped to ∼4×10 32 erg s −1 (0.5 -10 keV), comparable with the lowest luminosities ever detected from this source, despite the observations being taken near to periastron. We consider the possible orbital geometry of IGR J17544−2619 and the implications for the nature of the mass transfer and accretion mechanisms for both IGR J17544−2619 and the SFXT population. We conclude that accretion under the 'quasi-spherical accretion' model provides a good description of the behaviour of IGR J17544−2619, and suggest an additional mechanism for generating outbursts based upon the mass accumulation rate in the hot shell (atmosphere) that forms around the NS under the quasi-spherical formulation. Hence we hope to aid in explaining the varied outburst behaviours observed across the SFXT population with a consistent underlying physical model.

Temporal analysis of INTEGRAL/IBIS data has revealed a 5.7195±0.0007 day periodicity in the supergiant fast X-ray transient (SFXT) source AX J1845.0−0433, which we interpret as the orbital period of the system. The new-found knowledge of the orbital period is utilised to investigate the geometry of the system by means of estimating an upper limit for the size of the supergiant (< 27R ⊙ ) as well as the eccentricity of the orbit (ǫ < 0.37).

We present the results of a 30 ks XMM-Newton observation of the supergiant fast X-ray transient (SFXT) SAX J1818.6−1703 − the first in-depth soft X-ray study of this source around periastron. INTEGRAL observations shortly before and after the XMM-Newton observation show the source to be in an atypically active state. Over the course of the XMM-Newton observation, the source shows a dynamic range of ∼ 100 with a luminosity greater than 1 × 10 35 erg s −1 for the majority of the observation. After an ∼6 ks period of low luminosity (∼ 10 34 erg s −1 ) emission, SAX J1818.6−1703 enters a phase of fast flaring activity, with flares ∼250 s long, separated by ∼2 ks. The source then enters a larger flare event of higher luminosity and ∼8 ks duration. Spectral analysis revealed evidence for a significant change in spectral shape during the observation with a photon index varying from Γ ∼ 2.5 during the initial low luminosity emission phase, to Γ ∼ 1.9 through the fast flaring activity, and a significant change to Γ ∼ 0.3 during the main flare. The intrinsic absorbing column density throughout the observation (n H ∼ 5×10 23 cm −2 ) is among the highest measured from an SFXT, and together with the XMM-Newton and INTEGRAL luminosities, consistent with the neutron star encountering an unusually dense wind environment around periastron. Although other mechanisms cannot be ruled out, we note that the onset of the brighter flares occurs at 3×10 35 erg s −1 , a luminosity consistent with the threshold for the switch from a radiative-dominated to Compton cooling regime in the quasi-spherical settling accretion model.

We present the results of combined INTEGRAL and XMM-Newton observations of the supergiant fast X-ray transient (SFXT) IGR J17354−3255. Three XMM-Newton observations of lengths 33.4 ks, 32.5 ks and 21.9 ks were undertaken, the first an initial pointing to identify the correct source in the field of view and the latter two performed around periastron. Simultaneous INTEGRAL observations across ∼ 66% of the orbital cycle were analysed but the source was neither detected by IBIS/ISGRI nor by JEM-X. The XMM-Newton light curves display a range of moderately bright X-ray activity but there are no particularly strong flares or outbursts in any of the three observations. We show that the spectral shape measured by XMM-Newton can be fitted by a consistent model throughout the observation, suggesting that the observed flux variations are driven by obscuration from a wind of varying density rather than changes in accretion mode. The simultaneous INTEGRAL data rule out simple extrapolation of the simple powerlaw model beyond the XMM-Newton energy range.