The rapid circularization and synchronization of the stellar components in an eccentric binary system at the onset of Roche lobe overflow is a fundamental assumption common to all binary stellar ...evolution and population synthesis codes, even though the validity of this assumption is questionable both theoretically and observationally. Here we calculate the evolution of the orbital elements of an eccentric binary through the direct three-body integration of a massive particle ejected through the inner Lagrangian point of the donor star at periastron. The trajectory of this particle leads to three possible outcomes: direct accretion onto the companion star within a single orbit, self-accretion back onto the donor star within a single orbit, or a quasi-periodic orbit around the companion star, possibly leading to the formation of a disk. We calculate the secular evolution of the binary orbit in the first two cases and conclude that direct impact accretion can increase as well as decrease the orbital semimajor axis and eccentricity, while self-accretion always decreases the orbital semimajor axis and eccentricity. In cases where mass overflow contributes to circularizing the orbit, circularization can set in on timescales as short as a few percent of the mass-transfer timescale. In cases where mass overflow increases the eccentricity, the orbital evolution is governed by competition between mass overflow and tidal torques. In the absence of tidal torques, mass overflow results in direct impact can lead to substantially subsynchronously rotating donor stars. Contrary to assumptions common in the literature, direct impact accretion furthermore does not always provide a strong sink of orbital angular momentum in close mass-transferring binaries; in fact, we instead find that a significant part can be returned to the orbit during the particle orbit. The formulation presented in this paper together with our previous work can be combined with stellar and binary evolution codes to generate a better picture of the evolution of eccentric, Roche lobe overflowing binary star systems.
We investigate the secular evolution of the orbital semimajor axis and eccentricity due to mass transfer in eccentric binaries, allowing for both mass and angular momentum loss from the system. ...Adopting a delta function mass transfer rate at the periastron of the binary orbit, we find that, depending on the initial binary properties at the onset of mass transfer, the orbital semimajor axis and eccentricity can either increase or decrease at a rate linearly proportional to the magnitude of the mass transfer rate at periastron. The range of initial binary mass ratios and eccentricities that lead to increasing orbital semimajor axes and eccentricities broadens with increasing degrees of mass loss from the system and narrows with increasing orbital angular momentum loss from the binary. Comparison with tidal evolution timescales shows that the usual assumption of rapid circularization at the onset of mass transfer in eccentric binaries is not justified, irrespective of the degree of systemic mass and angular momentum loss. This work extends our previous results for conservative mass transfer in eccentric binaries and can be incorporated into binary evolution and population synthesis codes to model non-conservative mass transfer in eccentric binaries.
Gravitational-wave signals from inspirals of binary compact objects (black holes and neutron stars) are primary targets of the ongoing searches by ground-based gravitational-wave interferometers ...(LIGO, Virgo and GEO-600). We present parameter-estimation simulations for inspirals of black-hole-neutron-star binaries using Markov-chain Monte Carlo methods. As a specific example of the power of these methods, we consider source localization in the sky and analyze the degeneracy in it when data from only two detectors are used. We focus on the effect that the black-hole spin has on the localization estimation. We also report on a comparative Markov-chain Monte Carlo analysis with two different waveform families, at 1.5 and 3.5 post-Newtonian orders.
In view of the recent measurement of the scintillation velocity for PSR J0737-3039, we examine the complete set of constraints imposed on the pulsar B natal kicks (magnitude and orientation) and ...predict the most favorable pulsar kick velocity and spin tilt for both isotropic and polar kicks. Our analysis takes into account both currently unknown parameters: the orientation of the orbital plane on the sky () and the radial component of the systemic velocity (V sub(r)). Assuming that the system's peculiar velocity is entirely due to the second supernova explosion, we find that the system may have crossed the Galactic plane multiple times since the birth of the second neutron star and that the postsupernova peculiar velocity could have been as high as 1200 km s super(-1). We also confirm the absolute lower and upper limits on the physical parameters derived in our earlier study. For specific combinations of the two unknown parameters and V sub(r), however, we find much tighter constraints on the presupernova binary configuration and natal kicks imparted to pulsar B, as well as on the age of system. Once is measured in the coming year, it will be straightforward to use the results presented here to further constrain the natal kicks and the spin-tilt predictions. We complete our comprehensive study and derive similar constraints and spin-tilt predictions for PSR B1534+12, for which the only free parameter is V sub(r). Finally, for PSR B1913+16 we update the progenitor and kick constraints using the measured pulsar spin tilt and allowing for Roche lobe overflow from the progenitor of the pulsar companion.
Although not nearly as numerous as binaries with two white dwarfs, eccentric neutron star-white dwarf (NS-WD) binaries are important gravitational-wave (GW) sources for the next generation of ...space-based detectors sensitive to low frequency waves. Here we investigate periastron precession in these sources as a result of general relativistic, tidal, and rotational effects; such precession is expected to be detectable for at least some of the detected binaries of this type. Currently, two eccentric NS-WD binaries are known in the galactic field, PSR J1141-6545 and PSR B2303+46, both of which have orbits too wide to be relevant in their current state to GW observations. However, population synthesis studies predict the existence of a significant Galactic population of such systems. Though small in most of these systems, we find that tidally induced periastron precession becomes important when tides contribute to more than 3% of the total precession rate. For these systems, accounting for tides when analyzing periastron precession rate measurements can improve estimates of the inferred WD component mass and, in some cases, will prevent us from misclassifying the object. However, such systems are rare, due to rapid orbital decay. To aid the inclusion of tidal effects when using periastron precession as a mass measurement tool, we derive a function that relates the WD radius and periastron precession constant to the WD mass.
In recent years, an increasing number of proper motions have been measured for Galactic X-ray binaries. When supplemented with accurate determinations of the component masses, orbital period, and ...donor effective temperature, these kinematical constraints harbor a wealth of information on the system's past evolution. Here, we consider all this available information to reconstruct the full evolutionary history of the black hole X-ray binary XTE J1118 + 480, assuming that the system originated in the Galactic disk and the donor has solar metallicity. This analysis accounts for four evolutionary phases: mass transfer through the ongoing X-ray phase, tidal evolution before the onset of Roche lobe overflow, motion through the Galactic potential after the formation of the black hole, and binary orbital dynamics due to explosive mass loss and possibly a black hole natal kick at the time of core collapse. We find that right after black hole formation, the system consists of a 6.0-10.0 M black hole and a 1.0-1.6 M main-sequence star. We also find that that an asymmetric natal kick is not only plausible but required for the formation of this system, and derive a lower and upper limit on the black hole natal kick velocity magnitude of and , respectively.
Inspiral signals from binary compact objects (black holes and neutron stars) are primary targets of the ongoing searches by ground-based gravitational-wave interferometers (LIGO, Virgo, and GEO-600). ...We present parameter-estimation simulations for inspirals of black hole-neutron star binaries using Markov Chain Monte Carlo methods. For the first time, we both estimated the parameters of a binary inspiral source with a spinning, precessing component and determined the accuracy of the parameter estimation, for simulated observations with ground-based gravitational-wave detectors. We demonstrate that we can obtain the distance, sky position, and binary orientation at a higher accuracy than previously suggested in the literature. For an observation of an inspiral with sufficient spin and two or three detectors we find an accuracy in the determination of the sky position of the order of tens of square degrees.
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