The 17 min orbital period in the Ultra Compact X-ray Binary 4U 0513-40

The ultracompact low-mass X-ray binary 4U 0513-40 in the globular cluster NGC1851 exhibits large amplitude X-ray flux variations with spectral changes from low/hard to high/soft states which have not been reported previously in other ultracompact X-ray binaries. Using BeppoSAX, CHANDRA and XMM Newton archival data together with recent INTEGRAL observations, we reveal a clear sinusoidal periodic signal with a period of ~17 minutes when the source is in a typical high/soft state with a dominant soft thermal component. The periodicity disappears when the source is in a low/hard state and the thermal soft component is not required any more to model the data. These properties indicate the orbital nature of the detected signal and imply an high inclination angle of the binary system (>80{\deg}).Comment: accepted MNRAS 201

INTEGRAL high energy behaviour of 4U 1812-12

The low mass X-ray binary system 4U 1812-12 was monitored with the INTEGRAL observatory in the period 2003-2004 and with BeppoSAX on April 20, 2000. We report here on the spectral and temporal analysis of both persistent and burst emission. The full data set confirms the persistent nature of this burster, and reveals the presence of emission up to 200 keV. The persistent spectrum is well described by a comptonization (CompTT) model plus a soft blackbody component. The source was observed in a hard spectral state with a 1-200 keV luminosity of 2*10^(36) ergs/s and L/LEdd~1% and no meaningful flux variation has been revealed, as also confirmed by a 2004 RXTE observation. We have also detected 4 bursts showing double peaked profiles and blackbody spectra with temperatures ranging from 1.9 to 3.1 keV.Comment: 6 pages, 4 figures. Accepted for publication by A&

XMM-Newton observations of unidentified INTEGRAL/IBIS sources

About 30% of the sources in the 4th INTEGRAL-IBIS catalogue are unidentified in that they lack an optical counterpart. To be able to classify them, X-ray observations are of crucial importance as they can place tighter constraints on the high energy error box, which is usually of the order of a few arcminutes, and allow their broad band spectrum to be studied. To this aim we have cross-correlated the list of all unidentified IBIS sources in the fourth catalogue with the archive of all XMM-Newton pointings, finding a set of 6 objects with archival data. For 1 of them, IGR J17331-2406, no X-ray source is detected by XMM inside the IBIS error box, most likely due to the fact that it is a transient object. In the case of IGR J17445-2747 two possible X-ray counterparts are found inside the IBIS error box: one is very weak while the other is bright but only detected once. In each of the remaining 4 cases: IGR J155359-5750, AX J1739.3-2923, AX J1740.2-2903 and IGR J18538-0102, we find instead a convincing association for which we provide an improved X-ray position and information on the optical/infrared counterpart. We also performed a detailed analysis of their XMM-IBIS spectra and on the basis of all information acquired we suggest that IGR J155359-5750 is an AGN of intermediate type, AX J1739.3-2923 and AX J1740.2-2903 are High Mass X-ray Binary systems, IGR J17331-2406 and IGR J17445-2747 are Galactic transient sources and IGR J18538-0102 could be a background AGN.Comment: 9 pages, 10 figures, accepted for publication on MNRAS main journa

Swift/XRT follow-up observations of unidentified INTEGRAL/IBIS sources

Many sources listed in the 4th IBIS/ISGRI survey are still unidentified, i.e. lacking an X-ray counterpart or simply not studied at lower energies (< 10 keV). The cross-correlation between the list of IBIS sources in the 4th catalogue and the Swift/XRT data archive is of key importance to search for the X-ray counterparts; in fact, the positional accuracy of few arcseconds obtained with XRT allows us to perform more efficient and reliable follow-up observations at other wavelengths (optical, UV, radio). In this work, we present the results of the XRT observations for four new gamma-ray sources: IGR J12123-5802, IGR J1248.2-5828, IGR J13107-5626 and IGR J14080-3023. For IGR J12123-5802 we find a likely counterpart, but further information are needed to classified this object, IGR J1248.2-5828 is found to be a Seyfert 1.9, for IGR J13107-5626 we suggest a possible AGN nature, while IGR J14080-3023 is classified as a Seyfert 1.5 galaxy.Comment: 6 pages, 4 figure and 2 tables. Accepted for publication on PoS (contribution PoS(extremesky2009)018), proceedings of "The Extreme sky: Sampling the Universe above 10 keV", held in Otranto (Italy), 13-17 October 200

The XMM Newton and INTEGRAL observations of the supergiant fast X-ray transient IGR J16328-4726

The accretion mechanism producing the short flares observed from the Supergiant Fast X-ray Transients (SFXT) is still highly debated and forms a major part in our attempts to place these X-ray binaries in the wider context of the High Mass X-ray Binaries. We report on a 216 ks INTEGRAL observation of the SFXT IGR J16328-4726 (August 24-27, 2014) simultaneous with two fixed-time observations with XMM Newton (33ks and 20ks) performed around the putative periastron passage, in order to investigate the accretion regime and the wind properties during this orbital phase. During these observations, the source has shown luminosity variations, from 4x10^{34} erg/s to 10^{36} erg/s, linked to spectral properties changes. The soft X-ray continuum is well modeled by a power law with a photon index varying from 1.2 up to 1.7 and with high values of the column density in the range 2-4x10^{23}/cm^2. We report on the presence of iron lines at 6.8-7.1 keV suggesting that the X-ray flux is produced by accretion of matter from the companion wind characterized by density and temperature inhomogeneities

Broadband X-ray spectrum of the newly discovered broad line radio galaxy IGR J21247+5058

In this paper we present radio and high energy observations of the INTEGRAL source IGR J21247+5058, a broad line emitting galaxy obscured by the Galactic plane. Archival VLA radio data indicate that IGR J21247+5058 can be classified as an FRII Broad Line Radio Galaxy. The spectrum between 610 MHz and 15 GHz is typical of synchrotron self-absorbed radiation with a peak at 8 GHz and a low energy turnover; the core fraction is 0.1 suggestive of a moderate Doppler boosting of the base of the jet. The high energy broad-band spectrum was obtained by combining XMM-Newton and Swift/XRT observation with INTEGRAL/IBIS data. The 0.4-100 keV spectrum is well described by a power law, with slope $\Gamma$=1.5, characterised by complex absorption due to two layers of material partially covering the source and a high energy cut-off around 70-80 keV. Features such as a narrow iron line and a Compton reflection component, if present, are weak, suggesting that reprocessing of the power law photons in the accretion disk plays a negligible role in the source.Comment: 7 pages, 7 figures, 3 tables, accepted for pubblication on MNRA

Hard X-ray selected giant radio galaxies - I. The X-ray properties and radio connection

We present the first broad-band X-ray study of the nuclei of 14 hard X-ray selected giant radio galaxies, based both on the literature and on the analysis of archival X-ray data from NuSTAR, XMM-Newton, Swift and INTEGRAL. The X-ray properties of the sources are consistent with an accretion-related X-ray emission, likely originating from an X-ray corona coupled to a radiatively efficient accretion flow. We find a correlation between the X-ray luminosity and the radio core luminosity, consistent with that expected for AGNs powered by efficient accretion. In most sources, the luminosity of the radio lobes and the estimated jet power are relatively low compared with the nuclear X-ray emission. This indicates that either the nucleus is more powerful than in the past, consistent with a restarting of the central engine, or that the giant lobes are dimmer due to expansion losses.Comment: 11 pages, 3 figures. Accepted for publication in MNRA