The 100-month<i>Swift</i>catalogue of supergiant fast X-ray transients

Romano, P.; Krimm, H. A.; Palmer, D. M.; Ducci, L.; Esposito, P.; Vercellone, S.; Evans, P. A.; Guidorzi, C.; Mangano, V.; Kennea, J. A.; Barthelmy, S. D.; Burrows, D. N.; Gehrels, N.

doi:10.1051/0004-6361/201322516

Cited by 58 publications

(66 citation statements)

References 91 publications

(130 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The outbursts of these sources last for a few hours at the most, and thus their activity duty cycle is estimated to be typically of a few percent (Lutovinov et al 2013;Romano et al 2011Romano et al , 2014aBozzo et al 2015). In virtually all SFXTs it has also been observed that X-ray flares reaching a luminosity of 1−10% of that of the brightest outbursts can occur at any time, displaying timing and spectral properties similar to those of the more luminous events (see, e.g., Sidoli et al 2008;Bozzo et al 2010;Bodaghee et al 2010;Romano et al 2013Romano et al , 2014b.…”

Section: Introductionmentioning

confidence: 99%

Clumpy wind accretion in supergiant neutron star high mass X-ray binaries

Bozzo

Oskinova

Feldmeier

et al. 2016

A&A

View full text Add to dashboard Cite

The accretion of the stellar wind material by a compact object represents the main mechanism powering the X-ray emission in classical supergiant high mass X-ray binaries and supergiant fast X-ray transients. In this work we present the first attempt to simulate the accretion process of a fast and dense massive star wind onto a neutron star, taking into account the effects of the centrifugal and magnetic inhibition of accretion ("gating") due to the spin and magnetic field of the compact object. We made use of a radiative hydrodynamical code to model the nonstationary radiatively driven wind of an O-B supergiant star and then place a neutron star characterized by a fixed magnetic field and spin period at a certain distance from the massive companion. Our calculations follow, as a function of time (on a total timescale of several hours), the transitions of the system through all different accretion regimes that are triggered by the intrinsic variations in the density and velocity of the nonstationary wind. The X-ray luminosity released by the system is computed at each time step by taking into account the relevant physical processes occurring in the different accretion regimes. Synthetic lightcurves are derived and qualitatively compared with those observed from classical supergiant high mass X-ray binaries and supergiant fast X-ray transients. Although a number of simplifications are assumed in these calculations, we show that taking into account the effects of the centrifugal and magnetic inhibition of accretion significantly reduces the average X-ray luminosity expected for any neutron star wind-fed binary. The present model calculations suggest that long spin periods and stronger magnetic fields are favored in order to reproduce the peculiar behavior of supergiant fast X-ray transients in the X-ray domain.

show abstract

Section: Introductionmentioning

confidence: 99%

Clumpy wind accretion in supergiant neutron star high mass X-ray binaries

Bozzo

Oskinova

Feldmeier

et al. 2016

A&A

View full text Add to dashboard Cite

show abstract

“…Supergiant fast X-ray transients (SFXTs) are high mass X-ray binaries (HMXBs) hosting a neutron star (NS) and an OB supergiant companion (Sguera et al 2005;Negueruela et al 2006) which display X-ray flares reaching, for a few hours, 10 36 −10 37 erg s −1 (see Romano et al 2014c, for a recent review). This is at odds with normal supergiant HMXBs, which display a fairly constant average luminosity with typical variations of a factor of 10−50 on time scales of a few hundred to thousands of seconds; SFXTs are also significantly subluminous with respect to classical Sg-HMXBs like Vela X-1 (Bozzo et al 2015), and show a dynamical range up to 5 orders of magnitude, as their luminosities can be as low as ∼10 32 erg s −1 during quiescence (e.g.…”

Section: Introductionmentioning

confidence: 99%

“…It has been showing large flux swings since its discovery (in 't Zand et al 2004;in 't Zand 2005;Rampy et al 2009;Romano et al 2014c), with the brightest flux recorded by Swift/XRT (Burrows et al 2005) during the 2013 June 28 outburst (Romano et al 2013a) at ∼6.5 × 10 −9 erg cm −2 s −1 (0.3−10 keV, unabsorbed) Tables 1 and 2, and Fig. 2 are available in electronic form at http://www.aanda.org corresponding to L ∼ 10 37 erg s −1 .…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Giant outburst from the supergiant fast X-ray transient IGR J17544−2619: accretion from a transient disc?

Romano

Bozzo

Mangano

et al. 2015

A&A

Self Cite

View full text Add to dashboard Cite

Supergiant fast X-ray transients (SFXTs) are high mass X-ray binaries associated with OB supergiant companions and characterized by an X-ray flaring behaviour whose dynamical range reaches 5 orders of magnitude on time scales of a few hundred to thousands of seconds. Current investigations concentrate on finding possible mechanisms to inhibit accretion in SFXTs and to explain their unusually low average X-ray luminosity. We present the Swift observations of an exceptionally bright outburst displayed by the SFXT IGR J17544−2619 on 2014 October 10 when the source achieved a peak luminosity of 3 × 10 38 erg s −1 . This extends the total source dynamic range to > ∼ 10 6 , the largest (by a factor of 10) recorded so far from an SFXT. Tentative evidence for pulsations at a period of 11.6 s is also reported. We show that these observations challenge, for the first time, the maximum theoretical luminosity achievable by an SFXT and propose that this giant outburst was due to the formation of a transient accretion disc around the compact object.

show abstract

“…They show high dynamic ranges (between 100 and 10,000, depending on the specific source; e.g. [46,47]) and their X-ray spectra in outburst are very similar to accreting pulsars in HMXBs. In fact, half of them have measured neutron star (NS) spin periods similar to those observed from persistent HMXBs (see [48] for a recent review).…”

Section: Sfxtsmentioning

confidence: 99%

Wind accretion: Theory and observations

et al. 2015

View full text Add to dashboard Cite

A review of wind accretion in high-mass X-ray binaries is presented. We focus on different regimes of quasi-spherical accretion onto a neutron star: supersonic (Bondi) accretion, which takes place when the captured matter cools down rapidly and falls supersonically towards the neutron-star magnetosphere, and subsonic (settling) accretion which occurs when the plasma remains hot until it meets the magnetospheric boundary. The two regimes of accretion are separated by a limit in X-ray luminosity at about 4 × 10 36 erg s −1 . In subsonic accretion, which works at lower luminosities, a hot quasi-spherical shell must form around the magnetosphere, and the actual accretion rate onto the neutron star is determined by the ability of the plasma to enter the magnetosphere due to the Rayleigh-Taylor instability. In turn, two regimes of subsonic accretion are possible, depending on the plasma cooling mechanism (Compton or radiative) near the magnetopshere. The transition from the high-luminosity regime with Compton cooling to the low-luminosity (L x 3 × 10 35 erg s −1 ) regime with radiative cooling can be responsible for the onset of the 'off states repeatedly observed in several low-luminosity slowly accreting pulsars, such as Vela X-1, GX 301-2 and 4U 1907+09. The triggering of the transition may be due to a switch in the X-ray beam pattern in response to a change in the optical depth in the accretion column with changing luminosity. We also show that in the settling accretion theory, bright X-ray flares (∼ 10 38 − 10 40 ergs) observed in supergiant fast X-ray transients (SFXT) may be produced by sporadic capture of magnetized stellar-wind plasma. At sufficiently low accretion rates, magnetic reconnection can enhance the magnetospheric plasma entry rate, resulting in copious production of X-ray photons, strong Compton cooling and ultimately in unstable accretion of the entire shell. A bright flare develops on the free-fall time scale in the shell, and the typical energy released in an SFXT bright flare corresponds to the mass of the shell.

show abstract

The 100-monthSwiftcatalogue of supergiant fast X-ray transients

Cited by 58 publications

References 91 publications

Clumpy wind accretion in supergiant neutron star high mass X-ray binaries

Clumpy wind accretion in supergiant neutron star high mass X-ray binaries

Giant outburst from the supergiant fast X-ray transient IGR J17544−2619: accretion from a transient disc?

Wind accretion: Theory and observations

Contact Info

Product

Resources

About