scholarly journals A WHITE DWARF-NEUTRON STAR RELATIVISTIC BINARY MODEL FOR SOFT GAMMA-RAY REPEATERS

2005 ◽  
Vol 14 (09) ◽  
pp. 1473-1484 ◽  
Author(s):  
HERMAN J. MOSQUERA CUESTA
Keyword(s):  
Mass Transfer ◽  
Neutron Star ◽  
Orbital Period ◽  
White Dwarf ◽  
Fundamental Mode ◽  
Gamma Ray ◽  
High Mass ◽  
Integer Number ◽  
Binary Separation ◽  
Massive Neutron Star

A scenario for soft gamma-ray repeaters (SGRs) is introduced in which gravitational radiation reaction (GRR) effects drive the dynamics of an ultrashort orbital period X-ray binary embracing a high-mass donor white dwarf (WD) to a rapidly rotating low magnetized massive neutron star (NS) surrounded by a thick, dense and massive accretion torus. Driven by GRR, over timescales of ΔTrep~ 10 years, the binary separation reduces, the WD overflows its Roche lobe and the mass transfer drives unstable the accretion disk around the NS. As the binary circular orbital period is a multiple integer number (m) of the period of the WD fundamental mode,37the WD is since long pulsating at its fundamental mode; and most of its harmonics, due to the tidal interaction with its NS orbital companion. Hence, when the powerful irradiation glows onto the WD; from the fireball ejected as part of the disk matter slumps onto the NS, it is partially absorbed. This huge energy excites other WD radial (p-mode) pulsations.34,35After each mass-transfer episode the binary separation (and orbital period) is augmented significantly1,5due to the binary's angular momentum redistribution. Thus a new adiabatic inspiral phase driven by GRR reaction starts which brings the binary close again, and the process repeats after a time span ΔTrep. This model allows to explain most of SGRs observational features: their recurrent activity, energetics of giant superoutbursts and quiescent stages, and particularly the intriguing subpulses discovered by BeppoSAX,10which are suggested here to be overtones of the WD radial fundamental mode (see the accompanying paper).31

scholarly journals Orbital evolution of neutron-star–white-dwarf binaries by Roche lobe overflow and gravitational wave radiation

2021 ◽  
Vol 503 (2) ◽  
pp. 2776-2790
Author(s):  
Shenghua Yu ◽  
Youjun Lu ◽  
C Simon Jeffery
Keyword(s):  
Mass Transfer ◽  
Neutron Star ◽  
Gravitational Wave ◽  
White Dwarf ◽  
Signal To Noise Ratio ◽  
Orbital Evolution ◽  
Roche Lobe ◽  
High Mass ◽  
Wave Radiation ◽  
Binary Evolution

ABSTRACT We investigate the effects of mass transfer and gravitational wave (GW) radiation on the orbital evolution of contact neutron-star–white-dwarf (NS–WD) binaries, and the detectability of these binaries by space GW detectors (e.g. Laser Interferometer Space Antenna, LISA; Taiji; Tianqin). A NS–WD binary becomes contact when the WD component fills its Roche lobe, at which the GW frequency ranges from ∼0.0023 to 0.72 Hz for WD with masses ∼0.05–1.4 M⊙. We find that some high-mass NS–WD binaries may undergo direct coalescence after unstable mass transfer. However, the majority of NS–WD binaries can avoid direct coalescence because mass transfer after contact can lead to a reversal of the orbital evolution. Our model can well interpret the orbital evolution of the ultra-compact X-ray source 4U 1820–30. For a 4-yr observation of 4U 1820–30, the expected signal-to-noise-ratio (SNR) in GW characteristic strain is ∼11.0/10.4/2.2 (LISA/Taiji/Tianqin). The evolution of GW frequencies of NS–WD binaries depends on the WD masses. NS–WD binaries with masses larger than 4U 1820–30 are expected to be detected with significantly larger SNRs. For a $(1.4+0.5) \, {\rm M}_{\odot }$ NS–WD binary close to contact, the expected SNR for a one week observation is ∼27/40/28 (LISA/Taiji/Tianqin). For NS–WD binaries with masses of $(1.4+\gtrsim 1.1) \, {\rm M}_{\odot }$, the significant change of GW frequencies and amplitudes can be measured, and thus it is possible to determine the binary evolution stage. At distances up to the edge of the Galaxy (∼100 kpc), high-mass NS–WD binaries will be still detectable with SNR ≳ 1.

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 Classical Novae in the Context of the Evolution of Cataclysmic Binaries

1990 ◽  
Vol 122 ◽  
pp. 313-324
Author(s):  
Hans Ritter
Keyword(s):  
Mass Transfer ◽  
White Dwarf ◽  
White Dwarfs ◽  
Mass Range ◽  
High Mass ◽  
Transfer Rates ◽  
Classical Novae ◽  
Secular Evolution ◽  
Cataclysmic Binaries ◽  
Nova Outbursts

AbstractIn this paper we explore to what extent the TNR model of nova outbursts and our current concepts of the formation and secular evolution of cataclysmic binaries are compatible. Specifically we address the following questions: 1) whether observational selection can explain the high white dwarf masses attributed to novae, 2) whether novae on white dwarfs in the mass range 0.6M⊙ ≲ M ≲ 0.9M⊙ can occur and how much they could contribute to the observed nova frequency, and 3) whether the high mass transfer rates imposed on the white dwarf in systems above the period gap can be accommodated by the TNR model of nova outbursts.

scholarly journals Modelling decretion discs in Be/X-ray binaries

2019 ◽  
Author(s):  
R O Brown ◽  
M J Coe ◽  
W C G Ho ◽  
A T Okazaki
Keyword(s):  
Neutron Star ◽  
Orbital Period ◽  
Major Axis ◽  
High Mass ◽  
Model Parameters ◽  
Be Stars ◽  
Semi Major Axis ◽  
X Ray ◽  
Smoothed Particle ◽  
X Ray Binaries

Abstract As the largest population of high mass X-ray binaries, Be/X-ray binaries provide an excellent laboratory to investigate the extreme physics of neutron stars. It is generally accepted that Be stars possess a circumstellar disc, providing an additional source of accretion to the stellar winds present around young hot stars. Interaction between the neutron star and the disc is often the dominant accretion mechanism. A large amount of work has gone into modelling the properties of these circumstellar discs, allowing for the explanation of a number of observable phenomena. In this paper, smoothed particle hydroynamics simulations are performed whilst varying the model parameters (orbital period, eccentricity, the mass ejection rate of the Be star and the viscosity and orientation of the disc). The relationships between the model parameters and the disc’s characteristics (base gas density, the accretion rate of the neutron star and the disc’s size) are presented. The observational evidence for a dependency of the size of the Be star’s circumstellar disc on the orbital period (and semi-major axis) is supported by the simulations.

scholarly journals Optical Low States of the Supersoft X-Ray Source RXJ0513.9–6951

1997 ◽  
Vol 163 ◽  
pp. 787-787
Author(s):  
K. Reinsch ◽  
A. van Teeseling ◽  
K. Beuermann ◽  
T.M.C. Abbott
Keyword(s):  
Mass Transfer ◽  
White Dwarf ◽  
Mass Transfer Rate ◽  
Central Star ◽  
High Mass ◽  
X Ray ◽  
Total Luminosity ◽  
Nuclear Burning ◽  
Sudden Decrease ◽  
Optical Flux

The transient luminous soft X-ray source RXJ0513.9–6951 (Schaeidt et al., 1993, A&A 270, L9) is a high-mass-transfer binary system (Cowley et al., 1993, ApJ 418, L63; Pakull et al., 1993, A&A 278, L39) with a probable orbital period of 0.76 days (Crampton et al., 1996, ApJ 456, 320). Here, we summarize the results of a quasi-simultaneous optical and X-ray monitoring (see Fig. 1). The sudden decrease of the optical flux, the accompanying reddening, and the turn-on in the soft X-ray band can be quantitatively described by variations in the irradiation of the accretion disk by the hot central star (Reinsch et al., 1996, A&A 309, L11). In this simple model, we consider a white dwarf with nuclear burning of accreted matter (van den Heuvel et al., 1992, A&A 262, 97), surrounded by a flat standard disk. In the optical high state, accretion at near-Eddington rate occurs and the white dwarf photospheric radius must be considerably expanded causing an enhanced illumination of the disk and the secondary. In the optical low state, the photosphere shrinks in response to a temporarily slightly reduced mass-transfer rate. At the same time, the effective temperature increases, and the soft X-ray flux becomes detectable with ROSAT. This model does not depend on the particular cause for the drop in the accretion rate and can describe the optical/ X-ray variability with the total luminosity changing by less than 20 %.

scholarly journals On the Evolution of the Nova-like Variable AE Aquarii

2004 ◽  
Vol 190 ◽  
pp. 300-306
Author(s):  
P. J. Meintjes
Keyword(s):  
Mass Transfer ◽  
Orbital Period ◽  
White Dwarf ◽  
Time Scale ◽  
Critical Mass ◽  
Current Phase ◽  
Thermal Activity ◽  
Secondary Star ◽  
Wind Theory ◽  
Mass Ejection

AbstractIt is shown here that the peculiar properties of AE Aqr can can be accounted for if the mass transfer from an evolved 0.7M⊙ secondary K4-5 star (qi ≈ 0.8, i.e. < 1) initiated when the orbital period of the binary was Porb,i ≈ 8.5 hours and the white dwarf period P*,i ≈ 1 hour. This resulted in a significant amount of orbital angular momentum being accreted by the white dwarf in an initial discless spin-up phase towards P* ≈ 0.1 Porb,i. This destabilized the mass transfer, resulting in a run-away mass transfer from the secondary that lasted for approximately 104 years, with the orbital period evolving to Porb ≈ 11 hours until a critical mass ratio of qcrit = 0.73 had been reached. In this phase the mass transfer from the secondary occurred at a rapid rate of approximately Ṁ2 ≈ 1020 g s-1, resulting in an accretion disc which spun-up the white dwarf to a period of approximately P* ≈ 33 s. For all q ≤ qcrit = 0.73 the mass transfer proceeded on the thermal time scale of the secondary star, i.e. at a much slower rate, resulting in the binary converging and forcing AE Aqr into the propeller phase. Applying stellar wind theory, this allow an estimate of the polar magnetic field of the secondary star, which is of the order of B° ≈ (1600 – 2000) G. It has been shown here that the duration of mass transfer phase q = qcrit → 0.67 (now) lasted for approximately tṀ2 ~ 107 years, similar to the spin-down time scale of the white dwarf, tsd = P*/P* ≈ 107 years. The propeller ejection of matter in the current phase results in the dissipation of mhd power of Lmhd ≈ 1034 erg s-1, probably channeled into mass ejection and non-thermal activity. This explains the non-thermal outbursts that are observed in radio wavelengths, and occasionally also in TeV energies, from AE Aqr.

scholarly journals Probing the stellar wind geometry in Vela X-1 with infrared interferometry

2012 ◽  
Vol 8 (S290) ◽  
pp. 197-198
Author(s):  
Élodie Choquet ◽  
Pierre Kervella ◽  
Jean-Baptiste Le Bouquin ◽  
Antoine Mérand ◽  
Xavier Haubois ◽  
...  
Keyword(s):  
Neutron Star ◽  
High Mass ◽  
Resolution Limit ◽  
X Ray ◽  
Upper Limit ◽  
Accretion Process ◽  
Massive Neutron Star ◽  
Infrared Interferometry ◽  
X Ray Binaries ◽  
K Band

AbstractHigh-mass X-ray Binaries (HMXBs) are keys to study stellar remnants that are otherwise extremely faint and difficult to observe when isolated. Vela X-1 is a well-known eclipsing HMXB composed of a very massive neutron star orbiting a B0.5I supergiant with a period of 9 days. The supergiant wind is the main feeding material for the accreting neutron star, and its properties are of prime interest to understand the physics at stakes in the accretion process.In order to characterize the geometry and physical properties of the dense wind at a scale of a few stellar radii, we obtained infrared interferometric observations of Vela X-1 in 2010 using the VLTI/AMBER instrument in the K band (2.2 μm), and in 2012 using the VLTI/PIONIER instrument in the H band (1.6 μm).Although the apparent disk of the supergiant and the orbital separation of the two objects are beyond the present resolution limit of the VLTI, the K-band observations partially resolve the wind envelope on the two longest baselines. We were able to measure the radius of 265±82 R⊙ for the circumstellar wind at a temperature of 1300 K, assuming a distance of 1.9 kpc. The H-band observations do not resolve the system, and we were able to set an upper limit of 112 R⊙ for the envelope radius at a temperature of 1800 K.

scholarly journals 1FGL J1417.7–4407: A LIKELY GAMMA-RAY BRIGHT BINARY WITH A MASSIVE NEUTRON STAR AND A GIANT SECONDARY

2015 ◽  
Vol 804 (1) ◽  
pp. L12 ◽  
Author(s):  
Jay Strader ◽  
Laura Chomiuk ◽  
C. C. Cheung ◽  
David J. Sand ◽  
Davide Donato ◽  
...  
Keyword(s):  
Neutron Star ◽  
Gamma Ray ◽  
Massive Neutron Star

scholarly journals Collimated outflows from long-lived binary neutron star merger remnants

2020 ◽  
Vol 495 (1) ◽  
pp. L66-L70 ◽  
Author(s):  
Riccardo Ciolfi
Keyword(s):  
Black Hole ◽  
Neutron Star ◽  
Gamma Ray ◽  
Gamma Ray Bursts ◽  
Spin Axis ◽  
Binary Neutron Star ◽  
Physical Conditions ◽  
Massive Neutron Star ◽  
Merger Event ◽  
First Time

ABSTRACT The connection between short gamma-ray bursts (SGRBs) and binary neutron star (BNS) mergers was recently confirmed by the association of GRB 170817A with the merger event GW170817. However, no conclusive indications were obtained on whether the merger remnant that powered the SGRB jet was an accreting black hole (BH) or a long-lived massive neutron star (NS). Here, we explore the latter case via BNS merger simulations covering up to 250 ms after merger. We report, for the first time in a full merger simulation, the formation of a magnetically driven collimated outflow along the spin axis of the NS remnant. For the system at hand, the properties of such an outflow are found largely incompatible with an SGRB jet. With due consideration of the limitations and caveats of our present investigation, our results favour a BH origin for GRB 170817A and SGRBs in general. Even though this conclusion needs to be confirmed by exploring a larger variety of physical conditions, we briefly discuss possible consequences of all SGRB jets being powered by accreting BHs.

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