scholarly journals Super-Eddington accretion discs with advection and outflows around magnetized neutron stars

2019 ◽  
Vol 626 ◽  
pp. A18 ◽  
Author(s):  
Anna Chashkina ◽  
Galina Lipunova ◽  
Pavel Abolmasov ◽  
Juri Poutanen
Keyword(s):  
Neutron Star ◽  
Neutron Stars ◽  
Mass Loss ◽  
Accretion Rate ◽  
Accretion Disc ◽  
Accretion Discs ◽  
X Ray ◽  
Radial Profiles ◽  
X Ray Binaries ◽  
Eddington Limit

We present a model for a super-Eddington accretion disc around a magnetized neutron star taking into account advection of heat and the mass loss by the wind. The model is semi-analytical and predicts radial profiles of all the basic physical characteristics of the accretion disc. The magnetospheric radius is found as an eigenvalue of the problem. When the inner disc is in radiation-pressure-dominated regime but does not reach its local Eddington limit, advection is mild, and the radius of the magnetosphere depends weakly on the accretion rate. Once it approaches the local Eddington limit the disc becomes advection-dominated, and the scaling for the magnetospheric radius with the mass accretion rate is similar to the classical Alfvén relation. Allowing for the mass loss in a wind leads to an increase in the magnetospheric radius. Our model can be applied to a wide variety of magnetized neutron stars accreting close to or above their Eddington limits: ultra-luminous X-ray pulsars, Be/X-ray binaries in outbursts, and other systems. In the context of our model we discuss the observational properties of NGC 5907 X-1, the brightest ultra-luminous pulsar currently known, and NGC 300 ULX1, which is apparently a Be/X-ray binary experiencing a very bright super-Eddington outburst.

scholarly journals Evolving neutron star+helium star systems to intermediate-mass binary pulsars

2019 ◽  
Vol 490 (1) ◽  
pp. 752-757 ◽  
Author(s):  
W Tang ◽  
D Liu ◽  
B Wang
Keyword(s):  
Neutron Star ◽  
Neutron Stars ◽  
Accretion Rate ◽  
Intermediate Mass ◽  
X Ray ◽  
Binary Pulsars ◽  
Orbital Periods ◽  
Helium Star ◽  
X Ray Binaries ◽  
Better Than

ABSTRACT Intermediate-mass binary pulsars (IMBPs) are composed of neutron stars (NSs) and CO/ONe white dwarfs (WDs). It is generally suggested that IMBPs evolve from intermediate-mass X-ray binaries (IMXBs). However, this scenario is difficult to explain the formation of IMBPs with orbital periods (Porb) less than 3 d. It has recently been proposed that a system consisting of an NS and a helium (He) star can form IMBPs with Porb less than 3 d (known as the NS+He star scenario), but previous works can only cover a few observed sources with short orbital periods. We aim to investigate the NS+He star scenario by adopting different descriptions of the Eddington accretion rate ($\skew4\dot{M}_{\rm Edd}$) for NSs and different NS masses (MNS) varying from $1.10$ to $1.80\, \rm M_{\odot }$. Our results can cover most of the observed IMBPs with short orbital periods and almost half of the observed IMBPs with long orbital periods. We found that $\skew4\dot{M}_{\rm Edd}$ ∝ MNS−1/3 could match the observations better than a specific value for all NSs. We also found that the final spin periods of NSs slightly decrease with the initial MNS. The observed parameters of PSR J0621+1002, which is one of the well-observed IMBPs whose pulsar mass has been precisely measured, can be reproduced by this work.

scholarly journals Super-Eddington Accretion in Black Hole X-Ray Binaries

2004 ◽  
Vol 194 ◽  
pp. 60-62
Author(s):  
M. R. Truss
Keyword(s):  
Black Hole ◽  
High Resolution ◽  
Mass Loss ◽  
Accretion Discs ◽  
X Ray ◽  
Extreme Variability ◽  
Hydrodynamical Simulations ◽  
X Ray Binaries ◽  
Eddington Limit ◽  
Very High

AbstractI present, very high resolution hydrodynamical simulations of accretion discs in black hole X-ray binaries accreting near the Eddington limit, including the effects of disc irradiation and mass loss. I show that the extreme variability displayed by sources such as GRS 1915+105 can be explained within the framework of an outburst in a partially irradiated, turbulent, disc.

scholarly journals Ultra-luminous X-ray sources as neutron stars propelling and accreting at super-critical rates in high-mass X-ray binaries

2018 ◽  
Vol 14 (S346) ◽  
pp. 259-263
Author(s):  
M. Hakan Erkut ◽  
K. Yavuz Ekşi
Keyword(s):  
Neutron Star ◽  
Neutron Stars ◽  
Critical Mass ◽  
Point Sources ◽  
High Mass ◽  
X Ray ◽  
Consistent Model ◽  
Nearby Galaxies ◽  
X Ray Binaries ◽  
Eddington Limit

AbstarctUltra-luminous X-ray sources (ULXs) are off-nuclear point sources in nearby galaxies with luminosities well exceeding the Eddington limit for stellar-mass objects. It has been recognized after the discovery of pulsating ULXs (PULXs) that a fraction of these sources could be accreting neutron stars in high-mass X-ray binaries (HMXBs) though the majority of ULXs are lacking in coherent pulsations. The earliest stage of some HMXBs may harbor rapidly rotating neutron stars propelling out the matter transferred by the massive companion. The spin-down power transferred by the neutron-star magnetosphere to the accretion disk at this stage can well exceed the Eddington luminosities and the system appears as a non-pulsating ULX. In this picture, PULXs appear as super-critical mass-accreting descendants of non-pulsating ULXs. We present this evolutionary scenario within a self-consistent model of magnetosphere-disk interaction and discuss the implications of our results on the spin and magnetic field of the neutron star.

Quiescent luminosities of accreting neutron stars-possibility of neutrino losses due to strong pion condensations

2018 ◽  
Vol 27 (08) ◽  
pp. 1850067 ◽  
Author(s):  
Yasuhide Matsuo ◽  
HeLei Liu ◽  
Masa-aki Hashimoto ◽  
Tsuneo Noda
Keyword(s):  
Neutron Star ◽  
Neutron Stars ◽  
Accretion Rate ◽  
Cooling Process ◽  
X Ray ◽  
Mass Accretion Rate ◽  
Star Models ◽  
Low Mass ◽  
X Ray Binaries

We construct the quiescent neutron star models in the evolutionary calculations. The X-ray luminosities have been derived in terms of the time-averaged mass accretion rate for various neutron star masses and surface compositions. We compare the quiescent luminosities observed from X-ray transients in low mass X-ray binaries, where the stellar evolutionary calculations of accreting neutron stars include neutrino cooling due to strong pion condensations. Our results based on the evolutionary calculations suggest that stronger cooling process would be necessary to be consistent with observations.

DO YOUNG NEUTRON STARS WHICH SHOW THEMSELVES AS AXPs AND SGRs ACCRETE?

2003 ◽  
Vol 12 (05) ◽  
pp. 825-831 ◽  
Author(s):  
S. O. TAGIEVA ◽  
E. YAZGAN ◽  
A. ANKAY
Keyword(s):  
Neutron Star ◽  
Neutron Stars ◽  
Supernova Explosion ◽  
X Ray ◽  
X Ray Binaries

We examined the fall-back disk models, and in general accretion, proposed to explain the properties of AXPs and SGRs. We checked the possibility of some gas remaining around the neutron star after a supernova explosion. We also compared AXPs and SGRs with the X-ray pulsars in X-ray binaries. We conclude that the existing models of accretion from a fall-back disk are insufficient to explain the nature of AXPs and SGRs.

scholarly journals Mass transfer on a nuclear timescale in models of supergiant and ultra-luminous X-ray binaries

2019 ◽  
Vol 628 ◽  
pp. A19 ◽  
Author(s):  
M. Quast ◽  
N. Langer ◽  
T. M. Tauris
Keyword(s):  
Mass Transfer ◽  
Black Hole ◽  
Neutron Star ◽  
Roche Lobe ◽  
High Mass ◽  
X Rays ◽  
X Ray ◽  
Mass Ratios ◽  
X Ray Binaries ◽  
Eddington Limit

Context. The origin and number of the Galactic supergiant X-ray binaries is currently not well understood. They consist of an evolved massive star and a neutron star or black-hole companion. X-rays are thought to be generated from the accretion of wind material donated by the supergiant, while mass transfer due to Roche-lobe overflow is mostly disregarded because the high mass ratios of these systems are thought to render this process unstable. Aims. We investigate how the proximity of supergiant donor stars to the Eddington limit, and their advanced evolutionary stage, may influence the evolution of massive and ultra-luminous X-ray binaries with supergiant donor stars (SGXBs and ULXs). Methods. We constructed models of massive stars with different internal hydrogen and helium gradients (H/He gradients) and different hydrogen-rich envelope masses, and exposed them to slow mass-loss to probe the response of the stellar radius. In addition, we computed the corresponding Roche-lobe overflow mass-transfer evolution with our detailed binary stellar evolution code, approximating the compact objects as point masses. Results. We find that a H/He gradient in the layers beneath the surface, as it is likely present in the well-studied donor stars of observed SGBXs, can enable mass transfer in SGXBs on a nuclear timescale with a black-hole or a neutron star accretor, even for mass ratios in excess of 20. In our binary evolution models, the donor stars rapidly decrease their thermal equilibrium radius and can therefore cope with the inevitably strong orbital contraction imposed by the high mass ratio. We find that the orbital period derivatives of our models agree well with empirical values. We argue that the SGXB phase may be preceded by a common-envelope evolution. The envelope inflation near the Eddington limit means that this mechanism more likely occurs at high metallicity. Conclusion. Our results open a new perspective for understanding that SGBXs are numerous in our Galaxy and are almost completely absent in the Small Magellanic Cloud. Our results may also offer a way to find more ULX systems, to detect mass transfer on nuclear timescales in ULX systems even with neutron star accretors, and shed new light on the origin of the strong B-field in these neutron stars.

scholarly journals Astrophysical implications of neutron star inspiral and coalescence

2020 ◽  
Vol 29 (11) ◽  
pp. 2041015
Author(s):  
John L. Friedman ◽  
Nikolaos Stergioulas
Keyword(s):  
Neutron Star ◽  
Equation Of State ◽  
Neutron Stars ◽  
Gamma Ray ◽  
Gamma Ray Bursts ◽  
Maximum Mass ◽  
X Ray ◽  
Spectral Bands ◽  
Heaviest Elements ◽  
X Ray Binaries

The first inspiral of two neutron stars observed in gravitational waves was remarkably close, allowing the kind of simultaneous gravitational wave and electromagnetic observation that had not been expected for several years. Their merger, followed by a gamma-ray burst and a kilonova, was observed across the spectral bands of electromagnetic telescopes. These GW and electromagnetic observations have led to dramatic advances in understanding short gamma-ray bursts; determining the origin of the heaviest elements; and determining the maximum mass of neutron stars. From the imprint of tides on the gravitational waveforms and from observations of X-ray binaries, one can extract the radius and deformability of inspiraling neutron stars. Together, the radius, maximum mass, and causality constrain the neutron-star equation of state, and future constraints can come from observations of post-merger oscillations. We selectively review these results, filling in some of the physics with derivations and estimates.

scholarly journals Torque Reversals in Disk Accreting Pulsars

1998 ◽  
Vol 15 (2) ◽  
pp. 250-253
Author(s):  
Jianke Li ◽  
Dayal T. Wickramasinghe
Keyword(s):  
Neutron Star ◽  
Binary System ◽  
Recent Work ◽  
Time Scale ◽  
Accretion Rate ◽  
Future Studies ◽  
X Ray ◽  
The Past ◽  
X Ray Binaries ◽  
Coherent Picture

AbstractX-ray binaries in which the accreting component is a neutron star commonly exhibit significant changes in their spin. In the system Cen X-3, a disk accreting binary system, the pulsar was observed to spin up at a rate ḟ = 8 × 10−13 Hz s−1 when averaged over the past twenty years, but significant fluctuations were observed above this mean. Recent BASTE observations have disclosed that these fluctuations are much larger than previously noted, and appeared to be a system characteristic. The change in the spin state from spin-up to spin-down or vice-versa occurs on a time scale that is much shorter than the instrument can resolve (≤1 d), but appears always to be a similar amplitude, and to occur stochastically. These observations have posed a problem for the conventional torque–mass accretion relation for accreting pulsars, because in this model the spin rate is closely related to the accretion rate, and the latter needs to be finely tuned and to change abruptly to explain the observations. Here we review recent work in this direction and present a coherent picture that explains these observations. We also draw attention to some outstanding problems for future studies.

Sign in / Sign up

Export Citation Format

Share Document