We have analyzed in a systematic way about nine years of INTEGRAL data (17-100 keV) focusing on Supergiant Fast X-ray Transients (SFXTs) and three classical High Mass X-ray Binaries (HMXBs). Our approach has been twofold: image based analysis, sampled over a ~ks time frame to investigate the long-term properties of the sources, and lightcurve based analysis, sampled over a 100s time frame to seize the fast variability of each source during its ~ks activity. We find that while the prototypical SFXTs (IGR J17544-2619, XTE J1739-302 and SAX J1818.6-1703) are among the sources with the lowest ~ks based duty cycle ($<$1% activity over nine years of data), when studied at the 100s level, they are the ones with the highest detection percentage, meaning that, when active, they tend to have many bright short-term flares with respect to the other SFXTs. To investigate in a coherent and self consistent way all the available results within a physical scenario, we have extracted cumulative luminosity distributions for all the sources of the sample. The characterization of such distributions in hard X-rays, presented for the first time in this work for the SFXTs, shows that a power-law model is a plausible representation for SFXTs, while it can only reproduce the very high luminosity tail of the classical HMXBs, and even then, with a significantly steeper power-law slope with respect to SFXTs. The physical implications of these results within the frame of accretion in wind-fed systems are discussed.

High mass

10.1093/mnras/stu191

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Citations (42)

Swift/XRT monitoring of the latest outburst from XMMUJ174716.1-281048

The astronomer's telegram (2007)

L. Sidoli P. Romano S. Mereghetti M. Del Santo

Swift

Source

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ATel #13483: Swift/XRT confirms new outburst from XTE J1739-285

E. Bozzo C. Sánchez‐Fernández C. Ferrigno V. Savchenko J. Chenevez

Swift

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Advances in Understanding High-Mass X-ray Binaries with INTEGRALand Future Directions

New Astronomy Reviews (2019)

P. Kretschmar Felix Fürst L. Sidoli E. Bozzo J. Alfonso-Garzón

High mass X-ray binaries are among the brightest X-ray sources in the Milky Way, as well as in nearby Galaxies. Thanks to their highly variable emissions and complex phenomenology, they have attracted the interest of the high energy astrophysical community since the dawn of X-ray Astronomy. In more recent years, they have challenged our comprehension of physical processes in many more energy bands, ranging from the infrared to very high energies. In this review, we provide a broad but concise summary of the physical processes dominating the emission from high mass X-ray binaries across virtually the whole electromagnetic spectrum. These comprise the interaction of stellar winds with the high gravitational and magnetic fields of compact objects, the behaviour of matter under extreme magnetic and gravity conditions, and the perturbation of the massive star evolutionary processes by presence in a binary system. We highlight the role of the INTEGRAL mission in the discovery of many of the most interesting objects in the high mass X-ray binary class and its contribution in reviving the interest for these sources over the past two decades. We show how the INTEGRAL discoveries have not only contributed to significantly increase the number of high mass X-ray binaries known, thus advancing our understanding of the population as a whole, but also have opened new windows of investigation that stimulated the multi-wavelength approach nowadays common in most astrophysical research fields. We conclude the review by providing an overview of future facilities being planned from the X-ray to the very high energy domain that will hopefully help us in finding an answer to the many questions left open after more than 18 years of INTEGRAL scientific observations.

High mass

10.1016/j.newar.2020.101546

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Citations (54)

XMMU J174716.1–281048: a “quasi-persistent” very faint X-ray transient?

Astronomy and Astrophysics (2007)

M. Del Santo L. Sidoli S. Mereghetti A. Bazzano A. Tarana

The X-ray transient XMMU J174716.1–281048 was serendipitously discovered with XMM-Newton in 2003. It lies about 0.9 degrees off the Galactic Centre and its spectrum shows a high absorption (~ cm-2). Previous X-ray observations of the source field performed in 2000 and 2001 did not detect the source, indicative of a quiescent emission at least two orders of magnitude fainter. The low luminosity during the outburst (~34 erg s-1 at 8 kpc) indicates that the source is a member of the “very faint X-ray transients” class. On 2005 March 22nd the INTEGRAL satellite caught a possible type-I X-ray burst from the new INTEGRAL source IGR J17464–2811, classified as fast X-ray transient. This source was soon found to be positionally coincident, within the uncertainties, with XMMU J174716.1–281048. Here we report data analysis of the X-ray burst observed with the IBIS and JEM-X telescopes and confirm the type-I burst nature. We also re-analysed XMM-Newton and Chandra archival observations of the source field. We discuss the implications of these new findings, particularly related to the source distance as well as the source classification.

X-ray transient

Ibis

Transient (computer programming)

10.1051/0004-6361:20077536

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Citations (52)

INTEGRAL discovery of unusually long broad-band X-ray activity from the Supergiant Fast X-ray Transient IGR J18483−0311

Monthly Notices of the Royal Astronomical Society (2015)

V. Sguera L. Sidoli A. J. Bird A. Bazzano

We report on a broad-band X-ray study (0.5–250 keV) of the Supergiant Fast X-ray Transient IGR J18483−0311 using archival INTEGRAL data and a new targeted XMM–Newton observation. Our INTEGRAL investigation discovered for the first time an unusually long X-ray activity (3–60 keV) which continuously lasted for at least ∼11 d, i.e. a significant fraction (∼60 per cent) of the entire orbital period, and spanned orbital phases corresponding to both periastron and apastron passages. This prolongated X-ray activity is at odds with the much shorter durations marking outbursts from classical SFXTs especially above 20 keV, as such it represents a departure from their nominal behaviour and it adds a further extreme characteristic to the already extreme SFXT IGR J18483−0311. Our IBIS/ISGRI high energy investigation (100–250 keV) of archival outbursts activity from the source showed that the recently reported hint of a possible hard X-ray tail is not real and it is likely due to noisy background. The new XMM–Newton targeted observation did not detect any sign of strong X-ray outburst activity from the source despite being performed close to its periastron passage, on the contrary IGR J18483−0311 was caught during the common intermediate X-ray state with a low-luminosity value of ∼3 × 1033 erg s−1 (0.5–10 keV). We discuss all the reported results in the framework of both spherically symmetric clumpy wind scenario and quasi-spherical settling accretion model.

X-ray transient

Orbital period

10.1093/mnras/stv341

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Spectral analysis of IGR J01572−7259 during its 2016 outburst

Monthly Notices of the Royal Astronomical Society (2017)

N. La Palombara P. Esposito S. Mereghetti Fabio Pintore L. Sidoli

We report on the results of the $XMM-Newton$ observation of IGR J01572-7259 during its most recent outburst in 2016 May, the first since 2008. The source reached a flux $f \sim 10^{-10}$ erg cm$^{-2}$ s$^{-1}$, which allowed us to perform a detailed analysis of its timing and spectral properties. We obtained a pulse period $P_{\rm spin}$ = 11.58208(2) s. The pulse profile is double peaked and strongly energy dependent, as the second peak is prominent only at low energies and the pulsed fraction increases with energy. The main spectral component is a power-law model, but at low energies we also detected a soft thermal component, which can be described with either a blackbody or a hot plasma model. Both the EPIC and RGS spectra show several emission lines, which can be identified with the transition lines of ionized N, O, Ne, and Fe and cannot be described with a thermal emission model. The phase-resolved spectral analysis showed that the flux of both the soft excess and the emission lines vary with the pulse phase: the soft excess disappears in the first pulse and becomes significant only in the second, where also the Fe line is stronger. This variability is difficult to explain with emission from a hot plasma, while the reprocessing of the primary X-ray emission at the inner edge of the accretion disk provides a realiable scenario. On the other hand, the narrow emission lines can be due to the presence of photoionized matter around the accreting source.

Spectral Analysis

10.1093/mnras/stx3283

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INTEGRAL observations of IGR J11215‐5952: the first Supergiant Fast X‐ray Transient displaying periodic outbursts

AIP conference proceedings (2007)

L. Sidoli A. Paizis S. Mereghetti

The hard X-ray source IGRJ11215-5952, discovered with INTEGRAL during a brief outburst in 2005, has been proposed as a new member of the class of Supergiant Fast X-ray Transients. Analysing archival INTEGRAL observations of the source field,we have discovered two previously unnoticed outbursts (in July 2003 and in May 2004),spaced by intervals of ~330 days, suggesting a possible orbital period.The 5-100keV spectrum is well described by a cut-off power law, with a photon index of 0.5, and a cut-off energy 15-20keV, typical of High Mass X-ray Binaries containing a neutron star. The luminosity is ~3E36erg/s assuming 6.2kpc, the distance of the likely optical counterpart, the blue supergiant HD306414.A fourth outburst was discovered in 2006 with XTE/PCA, 329 days after the third one, confirming the periodic nature of the source outbursts.Follow-up observations with Swift/XRT refined the source position and confirmed the association with HD306414.The 5-100keV spectrum, the recurrent nature of the outbursts, the blue supergiant companion star HD 306414, support the hypothesis that IGRJ11215-5952 is a Supergiant Fast X-ray Transient, and it is the first object of this class of High Mass X-ray Binaries displaying periodic outbursts.

X-ray transient

Blue supergiant

Compact star

10.1063/1.2774902

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Citations (1)

INTEGRAL and XMM-Newton study of the SFXT IGR J18483-0311 in quiescence: hint of a cyclotron emission feature?

V. Sguera L. Sidoli A. Bazzano L. Bassani M. Orlandini

Feature (linguistics)

Source

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