scholarly journals Identifying the formation mechanism of redback pulsars

2020 ◽  
Vol 493 (2) ◽  
pp. 2171-2177 ◽  
Author(s):  
M A De Vito ◽  
O G Benvenuto ◽  
J E Horvath
Keyword(s):  
Mass Transfer ◽  
Neutron Star ◽  
Formation Mechanism ◽  
Binary Systems ◽  
Close Binary ◽  
Formation Mechanisms ◽  
Orbital Periods ◽  
The Moment ◽  
Strong Evaporation ◽  
Theoretical Results

ABSTRACT We analyse the evolution of close binary systems containing a neutron star that lead to the formation of redback pulsars. Recently, there has been some debate on the origin of such systems and the formation mechanism of redbacks may still be considered as an open problem. We show that the operation of a strong evaporation mechanism, starting from the moment when the donor star becomes fully convective (or alternatively since the formation of the neutron star by accretion-induced collapse), produces systems with donor masses and orbital periods in the range corresponding to redbacks with donors appreciably smaller than their Roche lobes, i.e. they have low filling factors (lower than 0.75). Models of redback pulsars can be constructed assuming the occurrence of irradiation feedback. They have been shown to undergo cyclic mass transfer during the epoch at which they attain donor masses and orbital periods corresponding to redbacks, and stay in quasi-Roche lobe overflow conditions with high filling factors. We show that, if irradiation feedback occurs and radio ejection inhibits further accretion on to the neutron star after the first mass transfer cycle, the redback systems feature high filling factors. We suggest that the filling factor should be considered as a useful tool for discriminating among those redback formation mechanisms. We compare theoretical results with available observations and conclude that observations tend to favour models with high filling factors.

scholarly journals X-Ray Sources in Close Binary Systems

1974 ◽  
Vol 3 ◽  
pp. 89-107
Author(s):  
M. J. Rees
Keyword(s):  
Binary Systems ◽  
Close Binary ◽  
Rapid Variability ◽  
X Ray ◽  
Close Binary Systems ◽  
General Order ◽  
Typical Distances ◽  
Astronomical Research ◽  
Orbital Periods ◽  
Galactic Sources

The discovery by Giacconi and his colleagues of variable X-ray sources in close binary systems certainly ranks as one of the highlights of astronomical research during the last 3 years. These remarkable objects have already been extensively studied, by optical and radio observations as well as in the X-ray band; and they seem likely to prove as significant and far-reaching in their implications as pulsars.The ‘Third Uhuru Catalogue’ (Giacconi et al., 1973a) contains about 160 sources, of which about 100 lie in our Galaxy. Their distribution over the sky (together with other arguments) suggests that these sources have luminosities of the general order 1036–1038 erg s−1, and that their typical distances are ˜ 10kpc. These galactic sources generally display rapid variability. Little else is known about most of them, but they are probably of the same general class as systems such as Her X1, Cen X3, Cyg X1 and Cyg X3. These sources have been investigated in detail, and in all cases one infers a system where the X-ray source is orbiting around a relatively ordinary star. Six sources have been optically identified, and there are some others whose binary nature is established by the occurrence of an X-ray eclipse. Orbital periods range from 4.8 h (Cyg X3) up to ˜ 10 days.

scholarly journals High mass X-ray binaries as progenitors of gravitational wave sources

2018 ◽  
Vol 14 (S346) ◽  
pp. 417-425 ◽  
Author(s):  
Jakub Klencki ◽  
Gijs Nelemans
Keyword(s):  
Mass Transfer ◽  
Massive Star ◽  
Formation Rate ◽  
Point Of View ◽  
High Mass ◽  
Close Binary ◽  
X Ray ◽  
Orbital Periods ◽  
X Ray Binaries ◽  
Hubble Time

AbstractX-ray binaries with black hole (BH) accretors and massive star donors at short orbital periods of a few days can evolve into close binary BH (BBH) systems that merge within the Hubble time. From an observational point of view, upon the Roche-lobe overflow such systems will most likely appear as ultra-luminous X-ray sources (ULXs). To study this connection, we compute the mass transfer phase in systems with BH accretors and massive star donors (M > 15 Mʘ) at various orbital separations and metallicities. In the case of core-hydrogen and core-helium burning donors (cases A and C of mass transfer) we find the typical duration of super-Eddington mass transfer of up to 106 and 105 yr, with rates of 10−6 and 10−5Mʘ yr-1, respectively. Given that roughly 0.5 ULXs are found per unit of star formation rate, we estimate the rate of BBH mergers from stable mass transfer evolution to be at most 10 Gpc−3 yr−1.

scholarly journals Starspot Activity on Short-period RS CVn Stars

1991 ◽  
Vol 130 ◽  
pp. 370-372
Author(s):  
Michael Zeilik
Keyword(s):  
Binary Stars ◽  
Binary Systems ◽  
Magnetic Activity ◽  
Close Binary ◽  
Tidal Interactions ◽  
Rs Cvn Stars ◽  
Short Period ◽  
Basic Physics ◽  
Synchronous Rotation ◽  
Orbital Periods

We have yet to understand the magnetic activity cycles of cool close binary systems of sunlike stars. Mutual tidal interactions, as well as magnetic ones, may result from a regime of dynamo models not yet tested, because these have been developed for single stars. To arrive at the basic physics, though, requires that we first examine the phenomenology of magnetic activity for binary systems. In particular, we would like to discover if such activity has a clearly-defined cycle, such as the sun exibits.Among the proxy indicators of magnetic activity are the Ca II H and K lines. Strassmeier et al. (1988) used the strength of these lines as the primary criterion for the inclusion of systems in The Catalog of Chromospherically Binary Stars. Of the RS CVn stars in the catalog, 12 have orbital periods of one day or shorter; 9 are eclipsing systems. As part of a decade-long program, we have focussed our observations and models on eight of the short-period group (Hall, 1976): XY UMa, UV Psc, SV Cam, RT And, CG Cyg, ER Vul, BH Vir, and WY Cnc. These close systems are tidally-locked in synchronous rotation and tidally-distorted into Roche lobe configurations.

Close binary systems before and after mass transfer

1982 ◽  
Vol 87 (1-2) ◽  
pp. 377-401 ◽  
Author(s):  
F. Vansina ◽  
J. P. De Grève
Keyword(s):  
Mass Transfer ◽  
Binary Systems ◽  
Close Binary ◽  
Close Binary Systems ◽  
Before And After

scholarly journals CLOSE BINARY PROGENITORS OF HYPERNOVAE

2012 ◽  
Vol 08 ◽  
pp. 209-219 ◽  
Author(s):  
MAXIM V. BARKOV
Keyword(s):  
Magnetic Field ◽  
Black Hole ◽  
Neutron Star ◽  
Binary Systems ◽  
Close Binary ◽  
Transient Event ◽  
Common Envelope ◽  
Starting Point ◽  
The Common ◽  
Rayet Star

In this paper we propose a new plausible mechanism of supernova explosions specific to close binary systems. The starting point is the common envelope phase in the evolution of a binary consisting of a red super giant and a neutron star. As the neutron star spirals towards the center of its companion it spins up via disk accretion. Depending on the specific angular momentum of gas captured by the neutron star via the Bondi-Hoyle mechanism, it may reach millisecond periods either when it is still inside the common envelope or after it has merged with the companion core. The high accretion rate may result in strong differential rotation of the neutron star and generation of a magnetar-strength magnetic field. The magnetar wind can blow away the common envelope if its magnetic field is as strong as 1015 G, and can destroy the entire companion if it is as strong as 1016 G. The total explosion energy can be comparable to the rotational energy of a millisecond pulsar and reach 1052 erg. The result is an unusual type-II supernova with very high luminosity during the plateau phase, followed by a sharp drop in brightness and a steep light-curve tail. The remnant is either a solitary magnetar or a close binary involving a Wolf-Rayet star and a magnetar. When this Wolf-Rayet star explodes this will be a third supernovae explosion in the same binary. A particularly interesting version of the binary progenitor involves merger of a red super giant star with an ultra-compact companion, neutron star or black hole. In the case if a strong magnetic field is not generated on the surface of a neutron star then it will collapse to a black hole. After that we expect the formation of a very long-lived accretion disk around the black hole. The Blandford-Znajek driven jet from this black hole may drive not only hypernovae explosion but produce a bright X-ray transient event on a time scale of 104 s.

scholarly journals The origin of pulsating ultra-luminous X-ray sources: Low- and intermediate-mass X-ray binaries containing neutron star accretors

2020 ◽  
Vol 642 ◽  
pp. A174 ◽  
Author(s):  
D. Misra ◽  
T. Fragos ◽  
T. M. Tauris ◽  
E. Zapartas ◽  
D. R. Aguilera-Dena
Keyword(s):  
Mass Transfer ◽  
Neutron Star ◽  
Binary Systems ◽  
Mass Transfer Rate ◽  
Host Galaxy ◽  
Intermediate Mass ◽  
X Ray ◽  
Star Mass ◽  
X Ray Binaries ◽  
Eddington Limit

Context. Ultra-luminous X-ray sources (ULXs) are those X-ray sources located away from the centre of their host galaxy with luminosities exceeding the Eddington limit of a stellar-mass black hole (LX >  1039 erg s−1). Observed X-ray variability suggests that ULXs are X-ray binary systems. The discovery of X-ray pulsations in some of these objects (e.g. M82 X-2) suggests that a certain fraction of the ULX population may have a neutron star as the accretor. Aims. We present systematic modelling of low- and intermediate-mass X-ray binaries (LMXBs and IMXBs; donor-star mass range 0.92–8.0 M⊙ and neutron-star accretors) to explain the formation of this sub-population of ULXs. Methods. Using MESA, we explored the allowed initial parameter space of binary systems consisting of a neutron star and a low- or intermediate-mass donor star that could explain the observed properties of ULXs. These donors are transferring mass at super-Eddington rates while the accretion is limited locally in the accretion disc by the Eddington limit. Thus, our simulations take into account beaming effects and also include stellar rotation, tides, general angular momentum losses, and a detailed and self-consistent calculation of the mass-transfer rate. Results. Exploring the initial parameters that lead to the formation of neutron-star ULXs, we study the conditions that lead to dynamical stability of these systems, which depends strongly on the response of the donor star to mass loss. Using two values for the initial neutron star mass (1.3 M⊙ and 2.0 M⊙), we present two sets of mass-transfer calculation grids for comparison with observations of NS ULXs. We find that LMXBs/IMXBs can produce NS-ULXs with typical time-averaged isotropic-equivalent X-ray luminosities of between 1039 and 1041 erg s−1 on a timescale of up to ∼1.0 Myr for the lower luminosities. Finally, we estimate their likelihood of detection, the types of white-dwarf remnants left behind by the donors, and the total amount of mass accreted by the neutron stars. Conclusions. We show that observed super-Eddington luminosities can be achieved in LMXBs/IMXBs undergoing non-conservative mass transfer while assuming geometrical beaming. We also compare our results to the observed pulsating ULXs and infer their initial parameters. Our results suggest that a large subset of the observed pulsating ULX population can be explained by LMXBs/IMXBs in a super-Eddington mass-transfer phase.

scholarly journals Asteroseismology of Close Binary Stars: Tides and Mass Transfer

2021 ◽  
Vol 8 ◽  
Author(s):  
Zhao Guo
Keyword(s):  
Mass Transfer ◽  
Binary Stars ◽  
Binary Systems ◽  
Binary Star ◽  
Close Binary ◽  
Close Binaries ◽  
Linear Mode ◽  
Stellar Oscillations ◽  
Theoretical Approaches ◽  
Stellar Interiors

The study of stellar oscillations allows us to infer the properties of stellar interiors. Meanwhile, fundamental parameters such as mass and radius can be obtained by studying stars in binary systems. The synergy between binarity and asteroseismology can constrain the parameter space of stellar properties and facilitate the asteroseismic inference. On the other hand, binarity also introduces additional complexities such tides and mass transfer. From an observational perspective, we briefly review the recent advances in the study of tidal effects on stellar oscillations, focusing on upper main sequence stars (F-, A-, or OB- type). The effect can be roughly divided into two categories. The first one concerns the tidally excited oscillations (TEOs) in eccentric binaries where TEOs are mostly due to resonances between dynamical tides and gravity modes of the star. TEOs appear as orbital-harmonic oscillations on top of the eccentric ellipsoidal light curve variations (the “heartbeat” feature). The second category is regarding the self-excited oscillations perturbed by static tides in circularized and synchronized close binaries. It includes the tidal deformation of the propagation cavity and its effect on eigenfrequencies, eigenfunctions, and the pulsation alignment. We list binary systems that show these two types of tidal effect and summarize the orbital and pulsation observables. We also discuss the theoretical approaches used to model these tidal oscillations and relevant complications such as non-linear mode coupling and resonance locking. Further information can be extracted from the observations of these oscillations which will improve our understanding of tides. We also discuss the effect of mass transfer, the extreme result of tides, on stellar oscillations. We bring to the readers' attention: (1) oscillating stars undergoing mass accretion (A-, F-, and OB type pulsators and white dwarfs), for which the pulsation properties may be changed significantly by accretion; (2) post-mass transfer pulsators, which have undergone a stable or unstable Roche-Lobe overflow. These pulsators have great potential in probing detailed physical processes in stellar interiors and mass transfer, as well as in studying the binary star populations.

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