A Model for the Double System Containing the X-Ray Pulsar Her X-1

Бисноватый-Коган, Г. С.; Komberg, B. V.

doi:10.1017/s007418090001069x

Cited by 50 publications

(79 citation statements)

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“…11 by dots with error bars associated with uncertainty in thermal insulating envelope composition; data are taken from Gusakov, Chugunov & Kantor 2014b;Chugunov, Gusakov & Kantor 2017) reveal the inadequacy of the standard model: additional dissipation of r-modes is required to stabilize many observed NSs [i.e., all NSs in the white region of 11(a)]. Chugunov et al (2017) analyze the formation of MSPs via the recycling scenario (Bisnovatyi-Kogan & Komberg 1976;Alpar et al 1982;Bhattacharya & van den Heuvel 1991;Papitto et al 2013) and suggest 'minimal' constraints to the instability windows, which allow them to explain the observations of transiently accreting neutron stars, and the formation of high-frequency MSPs, simultaneously. The corresponding 'minimally constrained' instability window is shown in Fig.…”

Section: Upper Limit For Surface Temperature Of Msp 47 Tuc Aa and Conmentioning

confidence: 99%

Chandra studies of the globular cluster 47 Tucanae: a deeper X-ray source catalogue, five new X-ray counterparts to millisecond radio pulsars and new constraints to r-mode instability window

Bhattacharya

Heinke

Chugunov

et al. 2017

Monthly Notices of the Royal Astronomical Society

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We combined Chandra ACIS observations of the globular cluster 47 Tucanae (hereafter, 47 Tuc) from 2000, 2002, and 2014-15 to create a deeper X-ray source list, and study some of the faint radio millisecond pulsars (MSPs) present in this cluster. We have detected 370 X-ray sources within the half-mass radius (2 .79) of the cluster, 81 of which are newly identified, by including new data and using improved source detection techniques. The majority of the newly identified sources are in the crowded core region, indicating cluster membership. We associate five of the new X-ray sources with chromospherically active BY Dra or W UMa variables identified by Albrow et al. (2001). We present alternative positions derived from two methods, centroiding and image reconstruction, for faint, crowded sources. We are able to extract X-ray spectra of the recently discovered MSPs 47 Tuc aa, 47 Tuc ab, the newly timed MSP 47 Tuc Z, and the newly resolved MSPs 47 Tuc S and 47 Tuc F. Generally, they are well fit by black body or neutron star atmosphere models, with temperatures, luminosities and emitting radii similar to those of other known MSPs in 47 Tuc, though 47 Tuc aa and 47 Tuc ab reach lower X-ray luminosities. We limit X-ray emission from the full surface of the rapidly spinning (542 Hz) MSP 47 Tuc aa, and use this limit to put an upper bound for amplitude of r-mode oscillations in this pulsar as α < 2.5 × 10 −9 and constrain the shape of the r-mode instability window.

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Section: Upper Limit For Surface Temperature Of Msp 47 Tuc Aa and Conmentioning

confidence: 99%

Chandra studies of the globular cluster 47 Tucanae: a deeper X-ray source catalogue, five new X-ray counterparts to millisecond radio pulsars and new constraints to r-mode instability window

Bhattacharya

Heinke

Chugunov

et al. 2017

Monthly Notices of the Royal Astronomical Society

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“…Bisnovatyi-Kogan & Komberg (1974) suggested that pulsars in binaries may have low magnetic Ðelds because of this e †ect. Romani (1990Romani ( , 1995 outlined a picture in which matter initially accretes onto the polar cap, eventually spreads under the weight of the accumulated matter, and advects the magnetic Ðeld inward.…”

Section: Introductionmentioning

confidence: 99%

Magnetic Screening in Accreting Neutron Stars

Cumming

Zweibel

Bildsten

2001

ApJ

209

254

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We investigate whether the magnetic Ðeld of an accreting neutron star may be diamagnetically screened by the accreted matter. We assume the freshly accumulated material is unmagnetized and calculate the rate at which the intrinsic stellar magnetic Ñux is transported into it via Ohmic di †usion from below. For very high accretion rates (larger than the Eddington rate Brown & Bildsten have M 0 M 0 Edd ), shown that the liquid ocean and outer crust of the neutron star are built up on a timescale much shorter than the Ohmic penetration time. We extend their work to lower accretion rates and calculate the resulting screening of the magnetic Ðeld. We Ðnd that the Ohmic di †usion and accretion timescales are equal forWe calculate the one-dimensional steady state magnetic Ðeld proÐles and show M 0 B 0.1 M 0 Edd . that the magnetic Ðeld strength decreases as one moves up through the outer crust and ocean by n orders of magnitude, whereWe show that these proÐles are unstable to buoyancy n B M 0 /0.02 M 0 Edd . instabilities when G in the ocean, providing a new limit on the strength of the buried B Z 1010È1011 Ðeld. Our results have interesting implications for the weakly magnetic neutron stars in low-mass X-ray binaries. We Ðnd that magnetic screening is ine †ective for so that, no matter how the M 0 \ 10~2 M 0 Edd , accreted material joins onto the star, the underlying stellar Ðeld should always be evident. This is consistent with the fact that the only known persistently pulsing accreting X-ray millisecond pulsar, SAX J1808.4[3658, has an unusually low accretion rate of Although the simpliÐed magnetic M 0 D 10~3 M 0 Edd . and accretion geometry we adopt here does not allow us to deÐnitively say so, we are led to suggest that perhaps most of the weakly magnetic neutron stars in low-mass X-ray binaries have a screened magnetic Ðeld, explaining the lack of persistent pulsations from these sources. If screened, then the underlying Ðeld will emerge after accretion halts, on a timescale of only 100È1000 yr, set by the Ohmic di †usion time across the outer crust.

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“…Absence of radio pulsars in close binaries, in spite of intensive searches could be explained by the only reason: during accretion stage the magnetic field of the neutron star is screened by the inflowing accreting gas, so the recycled pulsar should have B ∼ 10 8 − 10 10 G, 2-4 orders of magnitude smaller than average field strength of radio pulsars. Discovery of the first binary pulsar [41], and subsequent discovery of more than 100 recycled pulsars [51,56] had confirmed this conclusion: all recycled pulsars have small values of magnetic fields, as was predicted in [20].…”

Section: Recycled Radio Pulsarsmentioning

confidence: 62%

“…Magnetic fields of radio pulsars estimated using (2.1) with observational values of P andṖ lay in a wide region between 10 8 and 10 13 G [55]. There are two distinctly different groups: single radio pulsars with periods exceeding 0.033 sec, and magnetic fields between 10 11 and 10 13 G, and recycled pulsars (RP), present or former members of close binary systems with millisecond periods and low magnetic fields between 10 8 and 10 10 G. Low magnetic field of recycled pulsars is probably a result of its damping during preceding accretion stage [20,22]. Lines of constant magnetic field (dashed), characteristic age (dash-dotted) and spin-down energy loss rate (dotted) are also shown.…”

Section: Radio Pulsarsmentioning

confidence: 99%

“…Detailed analysis of the fate of close X-ray binaries in low-mass systems, namely Her X-1, was done in [20], and the conclusion was made that evolution of such system will be ended by formation of a non-accreting neutron star in close binary, which should become a radio pulsar. It was shown, that neutron star rotation is accelerated during disk accretion stage, so the second time born (recycled) radio pulsar should become visible, provided it has a magnetic field similar to other single pulsars.…”

Section: Recycled Radio Pulsarsmentioning

confidence: 99%

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Evolutions of Neutron Stars and their Magnetic Fields

Бисноватый-Коган¹

2018

Proceedings of XII Multifrequency Behaviour of High Energy Cosmic Sources Workshop — PoS(MULTIF2017)

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Estimations of magnetic fields of neutron stars, observed as radio and X-ray pulsars, are discussed. It is shown, that theoretical and observational values for different types of radio pulsars are in good correspondence. Radio pulsars in close binaries and millisecond pulsars, which have passed the stage of disk accretion (recycled radio pulsars), have magnetic fields 2-4 orders of magnitude smaller than ordinary single pulsars. Most probably, the magnetic field of the neutron star was screened by the infalling material. Several screening models are considered. Formation of single recycled pulsars loosing its companion is discussed. Magnetic fields of some X-ray pulsars are estimated from the cyclotron line energy. In the case of Her X-1 this estimation exceeds considerably the value of its magnetic field obtained from long term observational data related to the beam structure evolution. Another interpretation of the cyclotron feature, based on the relativistic dipole radiation mechanism, could remove this discrepancy. Observational data about soft gamma repeaters and their interpretation as magnetars are critically analyzed.

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A Model for the Double System Containing the X-Ray Pulsar Her X-1

Cited by 50 publications

References 0 publications

Chandra studies of the globular cluster 47 Tucanae: a deeper X-ray source catalogue, five new X-ray counterparts to millisecond radio pulsars and new constraints to r-mode instability window

Chandra studies of the globular cluster 47 Tucanae: a deeper X-ray source catalogue, five new X-ray counterparts to millisecond radio pulsars and new constraints to r-mode instability window

Magnetic Screening in Accreting Neutron Stars

Evolutions of Neutron Stars and their Magnetic Fields

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