Propeller effect in two brightest transient X-ray pulsars: 4U 0115+63 and V 0332+53

Tsygankov, Sergey S.; Lutovinov, A.; Doroshenko, V.; Mushtukov, Alexander A.; Suleimanov, V.; Poutanen, Juri

doi:10.1051/0004-6361/201628236

Cited by 105 publications

(122 citation statements)

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“…This transition can be understood in terms of the thermal-viscous instability model as a moment when temperature at the outer radius of the accretion disk reached the critical temperature of ∼ 6500 K causing the decrease of the local viscosity and corresponding a decline of the mass accretion rate onto the compact object (see, e.g., Lasota 2001). This results in the fast decay of the luminosity observed, particularly, from XRPs in the very end of their outbursts (see recent works by Tsygankov et al 2016a;Lutovinov et al 2017). As can be seen from Fig.…”

Section: Resultsmentioning

confidence: 99%

SMC X-3: the closest ultraluminous X-ray source powered by a neutron star with non-dipole magnetic field

Tsygankov

Doroshenko

Lutovinov

et al. 2017

A&A

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102

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Aims. Magnetic field of accreting neutron stars determines their overall behavior including the maximum possible luminosity. Some models require an above-average magnetic field strength ( 10 13 G) in order to explain super-Eddington mass accretion rate in the recently discovered class of pulsating ultraluminous X-ray sources (ULX). The peak luminosity of SMC X-3 during its major outburst in 2016-2017 reached ∼ 2.5 × 10 39 erg s −1 comparable to that in ULXs thus making this source the nearest ULX-pulsar. Determination of the magnetic field of SMC X-3 is the main goal of this paper. Methods. SMC X-3 belongs to the class of transient X-ray pulsars with Be optical companions, and exhibited a giant outburst in July 2016 -March 2017. The source has been observed during the entire outburst with the Swift/XRT and Fermi/GBM telescopes, as well as the NuSTAR observatory. Collected data allowed us to estimate the magnetic field strength of the neutron star in SMC X-3 using several independent methods. Results. Spin evolution of the source during and between the outbursts and the luminosity of the transition to so-called propeller regime in the range of (0.3 − 7) × 10 35 erg s −1 imply relatively weak dipole field of (1 − 5) × 10 12 G. On the other hand, there is also evidence for much stronger field in the immediate vicinity of the neutron star surface. In particular, transition from super-to subcritical accretion regime associated with cease of the accretion column and very high peak luminosity favor an order of magnitude stronger field. This discrepancy makes SMC X-3 a good candidate to posses significant non-dipolar components of the field, and an intermediate source between classical X-ray pulsars and accreting magnetars which may constitute an appreciable fraction of ULX population.

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Section: Resultsmentioning

confidence: 99%

SMC X-3: the closest ultraluminous X-ray source powered by a neutron star with non-dipole magnetic field

Tsygankov

Doroshenko

Lutovinov

et al. 2017

A&A

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102

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“…We extracted the XRT light curves using the online XRT data products tool (Evans et al 2007(Evans et al , 2009, 2 which is shown in Figure 1 (red). Detailed analysis of the decay phase is presented by Tsygankov et al (2016a), who focusses on the transition from the direct accretion regime into the propeller state. This transition likely occurred when the decay rate accelerated, causing the sources to decrease rapidly in X-ray luminosity (Figure 1).…”

Section: Observations Analysis and Resultsmentioning

confidence: 99%

Meta-stable low-level accretion rate states or neutron star crust cooling in the Be/X-ray transients V0332+53 and 4U 0115+63

Wijnands

Degenaar

2016

Monthly Notices of the Royal Astronomical Society: Letters

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The Be/X-ray transients V0332+53 and 4U 0115+63 exhibited giant, type-II outbursts in 2015. Here we present Swift/XRT follow-up observations at the end of those outbursts. Surprisingly, the sources did not decay back to their known quiescent levels but stalled at a (slowly decaying) meta-stable state with luminosities a factor ∼10 above that observed in quiescence. The spectra in these states are considerably softer than the outburst spectra and appear to soften in time when the luminosity decreases. The physical mechanism behind these metastable states is unclear and they could be due to low-level accretion (either directly onto the neutron stars or onto their magnetospheres) or due to cooling of the accretion-heated neutron star crusts. Based on the spectra, the slowly decreasing luminosities, and the spectral softening, we favour the crust cooling hypothesis but we cannot exclude the accretion scenarios. On top of this meta-stable state, weak accretion events were observed that occurred at periastron passage and may thus be related to regular type-I outbursts.

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“…The 2.5−15 keV spectrum is well described by a single power law with the best-fit photon index Γ ∼ 2.0 ± 0.1, giving χ 2 = 24.3 for 32 degrees of freedom. Tsygankov et al (2016) of the BeXBs 4U 0115+63 and V 0332+53. These authors found that an absorbed blackbody with kT ≈ 0.5 keV described the low-state spectra well.…”

Section: Transition To the Propeller Regimementioning

confidence: 99%

“…For example, a fraction of matter may still leak through the barrier (Doroshenko et al 2011). Alternatively, high-energy radiation may also be detected as a thermal spectrum, which likely originates in the polar caps of the neutron star surface heated during intermittent accretion episodes or by non-uniform cooling of the neutron star surface after a recent outburst (Reig et al 2014;Tsygankov et al 2016). Deep crustal heating, where the crust of the neutron star cools by X-ray emission until it reaches thermal equilibrium, can also account for the emission at quiescence (Brown et al 1998;Wijnands et al 2013).…”

Section: Transition To the Propeller Regimementioning

confidence: 99%

Accretion regimes in the X-ray pulsar 4U 1901+03

Reig

Milonaki

2016

A&A

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Context. The source 4U 1901+03 is a high-mass X-ray pulsar than went into outburst in 2003. Observation performed with the Rossi X-ray Timing Explorer showed spectral and timing variability, including the detection of flares, quasi-periodic oscillations, complex changes in the pulse profiles, and pulse phase dependent spectral variability. Aims. We re-analysed the data covering the 2003 X-ray outburst and focused on several aspects of the variability that have not been discussed so far. These are the 10 keV feature and the X-ray spectral states and their association with accretion regimes, including the transit to the propeller state at the end of the outburst. Methods. We extracted light curves and spectra using data from the Rossi X-ray Timing Explorer. Low time resolution light curves were used to create hardness-intensity diagrams and study daily changes in flux. High time resolution light curves were used to create pulse profiles. An average spectrum per observation allowed us to investigate the evolution of the spectral parameters with time. Results. We find that 4U 1901+03 went through three accretion regimes over the course of the X-ray outburst. At the peak of the outburst and for a very short time, the X-ray flux may have overcome the critical limit that marks the formation of a radiative shock at a certain distance above the neutron star surface. Most of the time, however, the source is in the subcritical regime. Only at the end of the outburst, when the luminosity decreased below ∼10 36 (d/10 kpc) 2 erg s −1 , did the source enter the propeller regime. Evidence for the existence of these regimes comes from the pulse profiles, the shape of the hardness-intensity diagram, and the correlation of various spectral parameters with the flux. The 10 keV feature appears to strongly depend on the X-ray flux and on the pulse phase, which opens the possibility to interpret this feature as a cyclotron line.

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Propeller effect in two brightest transient X-ray pulsars: 4U 0115+63 and V 0332+53

Cited by 105 publications

References 58 publications

SMC X-3: the closest ultraluminous X-ray source powered by a neutron star with non-dipole magnetic field

SMC X-3: the closest ultraluminous X-ray source powered by a neutron star with non-dipole magnetic field

Meta-stable low-level accretion rate states or neutron star crust cooling in the Be/X-ray transients V0332+53 and 4U 0115+63

Accretion regimes in the X-ray pulsar 4U 1901+03

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