Propeller effect in action in the ultraluminous accreting magnetar M82 X−2

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

doi:10.1093/mnras/stw046

Cited by 155 publications

(177 citation statements)

References 35 publications

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“…In the opposite case, r m > r cor , the centrifugal drag by the magnetosphere at r m exceeds gravity, accretion is almost completely halted by the so-called propeller mechanism and the NS enters a regime in which the emitted luminosity is much lower (22,23,(43)(44)(45). …”

Section: Supplementary Textmentioning

confidence: 99%

An accreting pulsar with extreme properties drives an ultraluminous x-ray source in NGC 5907

Israel

Belfiore

Stella

et al. 2017

Science

406

386

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Ultraluminous x-ray sources (ULXs) in nearby galaxies shine brighter than any X-ray source in our Galaxy. ULXs are usually modeled as stellar-mass black holes (BHs) accreting at very high rates or intermediate-mass BHs. We present observations showing that NGC 5907 ULX is instead an x-ray accreting neutron star (NS) with a spin period evolving from 1.43 s in 2003 to 1.13 s in 2014. It has an isotropic peak luminosity of ∼1000 times the Eddington limit for a NS at 17.1 Mpc. Standard accretion models fail to explain its luminosity, even assuming beamed emission, but a strong multipolar magnetic field can describe its properties. These findings suggest that other extreme ULXs (x-ray luminosity ≥1041 erg s −1 ) might harbor NSs.Ultraluminous x-ray sources (ULXs) are observed in off-nucleus regions of nearby galaxiesand have x-ray luminosities in excess of a few 10 39 erg s −1 , which is the Eddington luminosity (L Edd ) for a black hole (BH) of 10 M (1). The L Edd sets an upper limit on the accretion luminosity (L acc ) of a compact object steadily accreting, since for L acc > L Edd accretion will be halted by radiation forces. For spherical accretion of fully ionized hydrogen, the limit can be written as, where σ T is the Thomson scattering cross section, m p is the proton mass, and M/M is the compact object mass in solar masses; for a 1.4 M neutron star (NS), the maximum accreting luminosity is ∼2×10 38 erg s −1 .The high luminosity of ULXs has thus been explained as accretion at or above the Eddington luminosity onto BHs of stellar origin (<80-100 M ), or onto intermediate-mass (10BHs (2, 3). However, if the emission of ULXs were beamed over a fraction b < 1 of the sky, their true luminosity, and thus also the compact object mass required not to exceed L Edd , would be reduced by the same factor. This possibility, together with the recent identification of two accreting NSs associated with the ∼10 40 erg s −1 M82 X-2 (4) and NGC 7793 P13 (5, 6) x-ray sources, have brought support to the view that most low-luminosity ULXs likely host a NS (7) 2 or a stellar-mass BH (8). For the most extreme ULXs with x-ray luminosity exceeding a few ×10 40 erg s −1 , BHs with masses in excess of 100 M are still commonly considered (9, 10).Despite several searches for coherent x-ray pulsations,no other ultraluminous x-ray source has been found to host a NS so far (11).Within the framework of "Exploring the X-ray Transient and variable Sky", EXTraS (12) Fig. 1 and Table 1). In all cases, a strong first period derivative term is present (see Table 1). The pulse shape is nearly sinusoidal, while the pulsed fraction (the semi-amplitude of the sinusoid divided by the average count rate)is energy dependent and increases from about 12% at low energies (<2.5 keV) to ∼20% in the hard band (>7 keV; Fig. 1).To derive constraints on the orbital period (P orb ), we applied a likelihood analysis to the two 2014 NuSTAR observations (see supplementary online text), which have the longest baseline. 3By assuming a circular orbit (as in the case of M...

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Section: Supplementary Textmentioning

confidence: 99%

An accreting pulsar with extreme properties drives an ultraluminous x-ray source in NGC 5907

Israel

Belfiore

Stella

et al. 2017

Science

406

386

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“…Figure 4 shows the correlation between the independently measured magnetic field strength and combination of the propeller limiting luminosity and the period, L lim P 7/3 , for four sources exhibiting transitions to the propeller regime. Measurements taken from the literature (for details see Tsygankov et al 2016) …”

Section: "Propeller" Effectmentioning

confidence: 99%

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

Tsygankov

Lutovinov

Doroshenko

et al. 2016

A&A

103

113

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Aims. We present the results of the monitoring programmes performed with the Swift/XRT telescope and aimed specifically to detect an abrupt decrease of the observed flux associated with a transition to the propeller regime in two well-known X-ray pulsars 4U 0115+63 and V 0332+53. Methods. Both sources form binary systems with Be optical companions and undergo so-called giant outbursts every 3-4 years. The current observational campaigns were performed with the Swift/XRT telescope in the soft X-ray band (0.5-10 keV) during the declining phases of the outbursts exhibited by both sources in 2015.Results. The transitions to the propeller regime were detected at the threshold luminosities of (1.4 ± 0.4) × 10 36 erg s −1 and (2.0 ± 0.4) × 10 36 erg s −1 for 4U 0115+63 and V 0332+53, respectively. Spectra of the sources are shown to be significantly softer during the low state. In both sources, the accretion at rates close to the aforementioned threshold values briefly resumes during the periastron passage following the transition into the propeller regime. The strength of the dipole component of the magnetic field required to inhibit the accretion agrees well with estimates based on the position of the cyclotron lines in their spectra, thus excluding presence of a strong multipole component of the magnetic field in the vicinity of the neutron star.

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“…In this case, the accretion onto the neutron star ceases, and only the radiation from the outer disk region R > R m is observed. In order for the propeller effect to operate in the systems being discussed, it is necessary that the neutron stars in them possess a very strong magnetic field B * ∼ 10 14 − 10 15 G similar to the field of magnetars (Tsygankov et al 2016a). …”

Section: Introductionmentioning

confidence: 99%

The nature of the bimodal luminosity distribution of ultraluminous X-ray pulsars

Гребенев

2017

Astron. Lett.

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The mechanism that can be responsible for the bimodal luminosity distribution of superEddington X-ray pulsars in binary systems is pointed out. The transition from the high to low state of these objects is explained by accretion flow spherization due to the radiation pressure at certain (high) accretion rates. The transition between the states can be associated with a gradual change in the accretion rate. The complex behavior of the recently discovered ultraluminous X-ray pulsars M 82 X-2, NGC 5907 ULX-1, and NGC 7793 P13 is explained by the proposed mechanism. The proposed model also naturally explains the measured spinup of the neutron star in these pulsars, which is slower than the expected one by several times.

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Propeller effect in action in the ultraluminous accreting magnetar M82 X−2

Cited by 155 publications

References 35 publications

An accreting pulsar with extreme properties drives an ultraluminous x-ray source in NGC 5907

An accreting pulsar with extreme properties drives an ultraluminous x-ray source in NGC 5907

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

The nature of the bimodal luminosity distribution of ultraluminous X-ray pulsars

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