Black Hole Companion Research Articles

Gravitational wave emission from a companion black hole in the presence of an accretion disc around a super-massive Kerr black hole

Gravitational wave signal characteristics from a binary black hole system in which the companion moves through the accretion disc of the primary are studied. We chose the primary to be a super-massive (M = 10 8 M ⊙ ) Kerr black hole and the companion to be a massive black hole (M = 10 5 M ⊙ ) to clearly demonstrate the effects. We show that the drag exerted on the companion by the disc is sufficient to reduce the coalescence time of the binary. The drag is primarily due to the fact that the accretion disc on a black hole deviates from a Keplerian disc and becomes sub-Keplerian due to inner boundary condition on the black hole horizon. We consider two types of accretion rates on to the companion. The companion is deeply immersed inside the disc and it can accrete at the Bondi rate which depends on the instantaneous density of the disc. However, an accretion disc can also form around the smaller black hole and it can accrete at its Eddington rate. Thus, this case is also studied and the results are compared. We find that the effect of the disc will be significant in reducing the coalescence time and one needs to incorporate this while interpreting gravitational wave signals emitted from such a binary system.

Long gamma-ray burst progenitors: boundary conditions and binary models

The observed association of Long Gamma-Ray Bursts (LGRBs) with peculiar Type Ic supernovae gives support to Woosley‘s collapsar/hypernova model, in which the GRB is produced by the collapse of the rapidly rotating core of a massive star to a black hole. The association of LGRBs with small star-forming galaxies suggests low-metallicity to be a condition for a massive star to evolve to the collapsar stage. Both completely-mixed single star models and binary star models are possible. In binary models the progenitor of the GRB is a massive helium star with a close companion. We find that tidal synchronization during core-helium burning is reached on a short timescale (less than a few millennia). However, the strong core-envelope coupling in the subsequent evolutionary stages is likely to rule out helium stars with main-sequence companions as progenitors of hypernovae/GRBs. On the other hand, helium stars in close binaries with a neutron-star or black-hole companion can, despite the strong core-envelope coupling in the post-helium burning phase, retain sufficient core angular momentum to produce a hypernova/GRB.

Hydro-without-hydro framework for simulations of black hole–neutron star binaries

We introduce a computational framework which avoids solving explicitly hydrodynamic equations and is suitable for studying the pre-merger evolution of black hole–neutron star binary systems. The essence of the method consists of constructing a neutron star model with a black hole companion and freezing the internal degrees of freedom of the neutron star during the course of the evolution of the spacetime geometry. We present the main ingredients of the framework, from the formulation of the problem to the appropriate computational techniques to study these binary systems. In addition, we present numerical results of the construction of initial data sets and evolutions that demonstrate the feasibility of this approach.

Relativistic Binary Pulsars with Black Hole Companions

Binaries containing a stellar mass black hole and a recycled radio pulsar have so far eluded detection. We present a focused investigation of the formation and evolution of these systems in the Galactic disk, highlighting the factors that limit their numbers and the reasons why they may be extremely rare. We surmise that the birthrate of black hole/recycled pulsar binaries in the Galactic disk is probably no higher than ~10-7 yr-1 and may be much less, including zero. Simple arguments regarding common-envelope evolution suggest that these binaries should have orbital periods <10 hr and an average lifetime of 108 yr before coalescence due to the emission of gravitational radiation. We expect that fewer than ~10 of these compact, relativistic binaries currently reside in the Galactic disk, less than 0.1%-1% of the number of double neutron stars. The discovery of two or more black hole/recycled pulsar binaries using current radio telescopes would tightly constrain certain ideas regarding the evolution of massive stars, dynamical mass transfer, and black hole formation.

The Evolution of Massive Stars: The Be Star and Microquasar Phenomena

Massive Oand B-type stars evolve significantly faster than stars with cooler spectral types, so their populations include stars at many different evolutionary stages. They provide fascinating laboratories for the study of stellar evolution. In this dissertation, I investigate an unevolved massive star system and two particular categories of evolved stars, Be stars and microquasars. The massive triple system HD 16429 A is largely unevolved, but I present it here as an example of the type of system that will eventually experience a disrupting supernova. I discuss the Doppler tomography technique that I used to isolate the two brightest components, and include my analysis of each star. The stationary component, HD 16429 Aa, is an O9.5 II star. The Ab1 component is a hotter yet less luminous O8 III–IV star, while the unseen Ab2 star is estimated to be a B0 star. Interestingly, HD 16429 A may be associated with the microquasar LS I 61 303. The two systems are only 3 .6 apart in the sky, and they may form a subcluster within the Cas OB6 association. Many massive binary systems, including Be binaries, contain the final product of massive stellar evolution: a neutron star or black hole companion. Mass transfer from the less evolved star onto the compact companion generates X-ray emission, and some of these massive X-ray binaries also have relativistic radio jets that closely resemble small versions of extragalactic quasars. Not only are these microquasars a good test bed for accretion disk and jet models, they also provide fascinating examples of stellar evolution. Based on its large eccentricity and runaway velocity, the microquasar LS 5039 appears to be a recent survivor of the supernova that formed the microquasar. In this dissertation, I derive many of its presupernova characteristics from a spectroscopic study of the system. Be stars are a class of B stars with circumstellar disks that cause Balmer and other line emission. The source of their disks is not well understood, but it is likely that a combination of rapid rotation and nonradial pulsations contribute to their formation. This phenomenon is observed both in pre–main-sequence and evolved B stars, although here I concentrate on main-sequence (MS) and post-MS Be stars. Recent evolutionary models of rapidly rotating massive stars have suggested that the Be phenomenon may be caused by an evolutionary spin-up toward the end of the MS lifetime. Alternatively, binary mass transfer may be responsible for the increase in rotational velocity that induces the Be star disks, although not all Be stars are observed in binary systems. A third possibility is that Be stars may be born as rapid rotators. To investigate these three Be star formation scenarios, I am performing a photometric survey of open clusters. In this work, I present the first results from 20 clusters. I do not find a strong relationship between the percentage of Be stars and the cluster age, but I do find more Be stars turning off the MS rather than close to the zeroage MS. This suggests that either evolutionary spin-up or binary mass transfer is responsible for the phenomenon. I also find a lower percentage of Be stars than other studies have found, although I show that this is probably due to the longterm variability of Be star disks and different sampling methods.

Black hole-neutron star binaries in general relativity: Quasiequilibrium formulation

We present a new numerical method for the construction of quasiequilibrium models of black hole-neutron star binaries. We solve the constraint equations of general relativity, decomposed in the conformal thin-sandwich formalism, together with the Euler equation for the neutron star matter. We take the system to be stationary in a corotating frame and thereby assume the presence of a helical Killing vector. We solve these coupled equations in the background metric of a Kerr-Schild black hole, which accounts for the neutron star's black hole companion. In this paper we adopt a polytropic equation of state for the neutron star matter and assume large black hole--to--neutron star mass ratios. These simplifications allow us to focus on the construction of quasiequilibrium neutron star models in the presence of strong-field, black hole companions. We summarize the results of several code tests, compare with Newtonian models, and locate the onset of tidal disruption in a fully relativistic framework.

A Comprehensive Study of Young Black Hole Populations

We present theoretical models of black hole (BH) populations in young stellar environments, such as starbursts and young star clusters. Using a population synthesis approach, we compute the formation rates and characteristic properties of single and binary BHs for various representative ages and choices of parameters. We find that most of the BHs (typically 80% for an initial 50% binary fraction) are single, but with many originating from primordial binaries (which either merged into a single massive star or were disrupted following a supernova explosion). A smaller but significant fraction (typically 20%) of the BHs remain in binary systems. Main-sequence stars are the most frequent BH companions, but massive BH-BH binaries are the next most numerous group. The most massive BHs found in our simulations reach ~80 M☉ and are formed through mergers of massive binary components. If formed in a dense star cluster, such a massive stellar BH may become the seed for growth to a more massive (intermediate-mass) BH. Although we do not include dynamical interactions, our results provide realistic initial conditions for N-body simulations of dense star clusters (e.g., globular clusters) including primordial BHs.

Recycled pulsars with black hole companions: the high-mass analogues of PSR B2303+46

We investigate the possibility that mass transfer early in the evolution of a massive binary can effect a reversal of the end states of the two components, resulting in a neutron star that forms before a black hole. In this sense, such systems would comprise the high-mass analogues of white dwarf-neutron star systems such as PSR B2303+46. One consequence of this reversal is that a second episode of mass transfer from the black hole progenitor star can recycle the nascent neutron star, extending the life of the pulsar.

Searching for Failed Supernovae with Astrometric Binaries

Stars in the mass range 8 Msun<M<30 Msun are thought to end their lives as luminous supernovae that leave behind a neutron star. However, if a substantial fraction of these stars instead ended as black-hole remnants, without producing a supernova (a `failed' supernova), how would one know? We show that, under plausible assumptions, the Hipparcos catalog should contain about 30 f_{fail} astrometric binaries with black-hole companions, where f_{fail} is the fraction of supernovae that fail. Since no black-hole astrometric binaries are found in Hipparcos, one might like to conclude that such failed supernovae are very rare. However, the most important assumption required for this argument, the initial companion mass function (ICMF) of G stars (the majority of Hipparcos stars) in the high-mass companion regime, is without any observational basis. We show how the ICMF of G stars can be measured using the Full-Sky Astrometric Explorer (FAME), thereby permitting an accurate measurement of the rate of supernovae that fail.

PSR J1740--3052: a pulsar with a massive companion

We report on the discovery of a binary pulsar, PSR J1740-3052, during the Parkes multibeam survey. Timing observations of the 570-ms pulsar at Jodrell Bank and Parkes show that it is young, with a characteristic age of 350 kyr, and is in a 231-day, highly eccentric orbit with a companion whose mass exceeds 11 M_sun. An accurate position for the pulsar was obtained using the Australia Telescope Compact Array. Near-infrared 2.2-um observations make with the telescopes at the Siding Spring observatory reveal a late-type star coincident with the pulsar position. However, we do not believe that this star is the pulsar's companion, because a typical star of this spectral type and required mass would extend beyond the pulsar's orbit. Furthermore, the measured advance of periastron of the pulsar suggests a more compact companion, for example, a main-sequence star with radius only a few times that of the sun. Such a companion is also more consistent with the small dispersion measure variations seen near periastron. Although we cannot conclusively rule out a black-hole companion, we believe the companion is probably an early B star, making the system similar to the binary PSR J0045-7319.

Frame Dragging and Other Precessional Effects in Black Hole Pulsar Binaries

For radio pulsars in orbit with a compact companion, pulsar timing observations have proved to be a powerful tool for identifying the physical nature of the companion. Unfortunately, perhaps the most intriguing system where such a tool could be used, a pulsar in orbit with a black hole, has yet to be discovered. In this paper we give a detailed investigation of what one can learn about the black hole companion via timing observations of the pulsar. We present an analytic calculation for the propagation delay caused by the frame-dragging effect and show that it has the same functional behavior as the modulation of the observed rotational phase of the pulsar caused by the deflection of the radio signals in the gravitational field of the companion (bending delay). Thus, contrary to statements of other authors, the frame-dragging delay is unlikely to be separately measurable in pulsar binaries where the companion is a stellar-mass black hole. We demonstrate, however, that the precession of the binary orbit caused by the relativistic spin-orbit coupling can lead to observable effects that can be used to set a lower limit to the black hole spin or possibly allow the determination of its magnitude and orientation. We give parameter estimates for two possible systems, a 10 M☉ black hole in orbit either with a young (~0.1 s) pulsar or with a millisecond pulsar. Finally, we discuss the measurability of the quadrupole moment of the rotating black hole companion that would test the presence of a Kerr black hole. As an interesting side result of our calculations, we can give a further argument why the companion of PSR J0045-7319 cannot be a Kerr black hole.

A search for X-ray evidence of a compact companion to the unusual Wolf-Rayet star HD 50896 (EZ CMa)

We analyze results of a ≈ 25 ksec ASCA X-ray observation of the unusual Wolf-Rayet star HD 50896 (= EZ CMa). This WN5 star shows optical and ultraviolet variability at a 3.766 day period, which has been interpreted as a possible signature of a compact companion. Our objective was to search for evidence of hard X-rays (≥ 5 keV) which could be present if the WN5 wind is accreting onto a compact object. The ASCA spectra are dominated by emission below 5 keV and show no significant emission in the harder 5–10 keV range. Weak emission lines are present, and the X-rays arise in an optically thin plasma which spans a range of temperatures from ≤ 0.4 keV up to at least ≈ 2 keV. Excess X-ray absorption above the interstellar value is present, but the column density is no larger than N H ∼ 10 22 cm −2. The absorption-corrected X-ray luminosity L x (0.5 −10 keV) = 10 32.85 erg s −1 gives L x L bol ≈ 10 −6 a value that is typical of WN stars. No X-ray variability was detected. Our main conclusion is that the X-ray properties of HD 50896 are inconsistent with the behavior expected for wind accretion onto a neutron star or black hole companion. Alternative models based on wind shocks can explain most aspects of the X-ray behavior, and we argue that the hotter plasma near ∼ 2 keV could be due to the WR wind shocking onto a normal (nondegenerate) companion.

On the Evolution of Low‐Mass X‐Ray Binaries under the Influence of a Donor Stellar Wind Induced by X‐Rays from the Accretor

In a low-mass X-ray binary (LMXB), an intense stellar wind from the mass donor may be a consequence of the absorption of X-rays from the mass-accreting neutron star or black hole, and such a wind could change the evolution of these binaries dramatically compared with the evolution of cataclysmic variables (CVs), which are close binaries in which the accretor is a white dwarf. An analytical study and numerical models show that, in the closest and brightest LMXBs, a relativistic companion can capture up to ~10% of the mass lost in the induced stellar wind (ISW) from the main-sequence or subgiant donor, and this is enough to keep the X-ray luminosity of a typical LMXB on the level of LX ~ 5000 L☉ and to accelerate the rotation of an old neutron star with a low magnetic field into the millisecond-period range. A self-sustained ISW may exist even if the donor does not fill its Roche lobe, but the system can be bright (LX > 100 L☉) only if the radius of the donor is a substantial fraction ( 0.8) of the Roche lobe radius. A lower limit on the Roche lobe filling factor follows from the circumstance that both the rate Ėwind at which work must be done to lift wind matter off the donor and the rate Ėabs at which the donor absorbs X-ray energy are proportional to ISW (the ISW mass-loss rate) and from the requirement that Ėwind 3 hr. In Algol-like LMXBs in the Galactic disk, the timescale for the evaporation (caused by the ISW) of the donor with a low-mass, degenerate helium core can be smaller than the timescale for the radial expansion of the donor owing to nuclear evolution, and the donor may never fill its Roche lobe. However, if progenitor binaries are initially wide enough, the donor may escape evaporation as a main-sequence star, and significant mass transfer may not occur until the secondary evolves into a giant with a degenerate helium core of large mass and fills its Roche lobe. In globular clusters, as a result of capture and exchange reactions, semidetached Algol-like LMXBs can be formed in which the donor can fill its Roche lobe even when its degenerate helium core is of small mass, and Roche lobe mediated mass transfer driven by the nuclear evolution of the donor can dominate over capture from the ISW. The numerical models formally imply the possible presence in the Galaxy of ~104 dim (LX ~ 1-100 L☉), long-period LMXBs or radio pulsars with low-mass ( ~0.05 M☉) companions. Since there are few, if any, known observational counterparts of these systems, it is necessary to invoke a mechanism or mechanisms to destroy their formal progenitors. Possible destruction mechanisms include: (1) evaporation driven by the radiation from the rapidly rotating pulsar into which the accretor has been transformed by accretion during the bright LMXB phase, and (2) a dynamical instability arising when the donor is almost completely convective and fills its Roche lobe. In the case of dynamical disruption, the donor may be transformed into the envelope of a Thorne-Żytkow (1975) object with a neutron star or black hole core or into a planet-forming disk around the neutron star or black hole. A few short-period (Porb < 3 hr) LMXBs do exist, and, in them, the donor may be a helium white dwarf of mass less than ~0.09 M☉. An ISW operating before the donor fills its Roche lobe may be responsible for reducing the mass of the white dwarf from an initial value of ≥0.13 M☉ to a value of ≤0.09 M☉, thus permitting stable mass exchange (at a rate smaller than the Eddington limiting rate) and evolution to longer periods to occur after the donor fills its Roche lobe. Another scenario relies on the collapse of a massive oxygen-neon white dwarf, which has accreted from a Roche lobe filling helium white dwarf. Problems that must be explored further in order to acquire a better understanding of the evolution of LMXBs include the formation of a corona around an irradiated low-mass main-sequence or degenerate dwarf star, accretion of ISW matter by a neutron star or black hole companion, the effect of an ISW on the MSW, formation of millisecond pulsars, complete evaporation of low-mass donors, disruption by tidal forces of a low-mass main-sequence star or a degenerate dwarf companion into a gas disk around the accretor, and the formation of planetary systems in the disk around neutron stars and or black holes in post-LMXB systems.

Pulse Arrival Times from Binary Pulsars with Rotating Black Hole Companions

We present a study of the gravitational time delay of arrival of signals from binary pulsar systems with rotating black hole companions. In particular, we investigate the strength of this effect (Shapiro delay) as a function of the inclination, eccentricity and period of the orbit, as well as the mass and angular momentum of the black hole. This study is based on direct numerical integration of null geodesics in a Kerr background geometry. We find that, for binaries with sufficiently high orbital inclinations ($> 89^o$) and compact companion masses $> 10 M_\odot$, the effect arising from the rotation of the black hole in the system amounts to a microsecond-level variation of the arrival times of the pulsar pulses. If measurable, this variation could provide a unique signature for the presence of a rotating black hole in a binary pulsar system.

The cyclic period variability in SW Cygni

view Abstract Citations (10) References (30) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Cyclic Period Variability in SW Cygni Berrington, Robert C. ; Hall, Douglas S. Abstract Timings of primary eclipse up through 1992 are collected, plus a few overlooked in earlier studies. Analysis show that, after decreasing until approximately equals 1919 and increasing since then, the period has now started decreasing again, with the inflection point of the O-C curve being approximately 1972. The shortest period was 4.5727 days, the longest 4.5732 days, with a full cycle length of 96 yr. Explanation by the time-delay efffect, due to orbital motion around a third body, would require an unseen black hole companion of greater than or equal to 10 solar mass. A magnetic cycle operating in the K-type subgiant, an active dynamo star because of its convection and rapid rotation, is the best explanation. Publication: The Astronomical Journal Pub Date: May 1994 DOI: 10.1086/116996 Bibcode: 1994AJ....107.1868B Keywords: Black Holes (Astronomy); Circles (Geometry); Cygnus Constellation; Eclipsing Binary Stars; Orbits; Periodic Variations; Variability; Curve Fitting; Ephemeris Time; Errors; Least Squares Method; Astronomy; BINARIES: ECLIPSING full text sources ADS | data products SIMBAD (2) CDS (1) Related Materials (1) Erratum: 1994AJ....108.1122B

A search for spectroscopic binaries among the runaway O type stars

Numerous radial velocity measurements of medium dispersion were made for the 10 brighter stars given in Stone's list of very probable O type runaways. All plates were measured with the KPNO PDS microdensitometer, and a new iterative reductional analysis was used to derive plate velocities, which are estimated to be 1.6 times more accurate internally than those found by using the traditional method. Of thse stars, psi Per, alpha Cam, HD 188209, and 26 Cep are identified as probable velocity variables, while 9 Sge, lambda Cep, and HD 218915 are classed as possible variables. If the source of this variability is Keplerian rather than atmospheric, which cannot be established unequivocally from the observations of this paper, psi Per could be a spectroscopic binary with a black hole companion, and at least 1.2 solar mass. The detection of runaway binary systems from radial velocity measurements is discussed.

The velocity-mass correlation of the O-type stars - Model results

This paper presents new model results describing the evolution of massive close binaries from their initial ZAMS to post-supernova stages. Unlike the previous conservative study by Stone (Astrophys. J. 232, 520 (1979) (Paper II)), these results allow explicitly for mass loss from the binary system occurring during the core hydrogen- and helium-burning stages of the primary binary star as well as during the Roche lobe overflow. Because of uncertainties in these rates, model results are given for several reasonable choices for these rates. All of the models consistently predict an increasing relation between the peculiar space velocities and masses for runaway OB stars which agrees well with the observed correlations discussed in Stone (Astron. J. 86, 544 (1981) (Paper III)) and also predict a lower limit at Mroughly-equal11M/sub sun/ for the masses of runaway stars, in agreement with the observational limit found by A. Blaauw (Bull. Astron. Inst. Neth. 15, 265, 1961), both of which support the binary-supernova scenario described by van den Heuvel and Heise for the origin of runaway stars. These models also predict that the more massive O stars will produce correspondingly more massive compact remnants, and that most binaries experiencing supernova-induced kick velocities of magnitude V/submore » k/> or approx. =300 km s/sup -1/ will disrupt following the explosions. The best estimate for this velocity as established from pulsar observations is V/sub k/roughly-equal150 km s/sup -1/, in which case probably only 15% if these binaries will be disrupted by the supernova explosions, and therefore, almost all runaway stars should have either neutron star or black hole companions.« less

The physical properties and orbital parameters of the B0 IA star HD 152667 = V861 Scorpii - A supergiant with a black hole companion

view Abstract Citations (13) References (37) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The physical properties and orbital parameters of the B0 Ia star HD 152667 = V861 Scorpii: a supergiant with a black hole companion? Wolff, S. C. ; Beichman, C. A. Abstract High-dispersion spectrograms are used to analyse the physical characteristics and orbital motion of the BO Ia binary RD 152667. The mass of the primary is found to be in the range 40-60 M0, and the minimum mass of the secondary is 12.5 + 2 M0. Infrared observations yield a mass loss rate of 5 x 10-6 M0 yr -1, and there is evidence that the stellar wind is enhanced near the inner Lagrangian point. Rotation appears to be slower than synchronous, and within the uncertainties of the estimates the stellar and tidal radii are comparable. If the identification of the companion to RD 152667 as an X-ray source is correct, then it is a good candidate for identification as a black hole. Subject headings: stars: binaries - stars: early-type - stars: individual - stars: supergiants - X-rays: binaries Publication: The Astrophysical Journal Pub Date: June 1979 DOI: 10.1086/157107 Bibcode: 1979ApJ...230..519W Keywords: Black Holes (Astronomy); Early Stars; Eclipsing Binary Stars; Orbital Elements; Physical Properties; Supergiant Stars; Abundance; Infrared Astronomy; Line Spectra; Radial Velocity; Stellar Luminosity; Stellar Mass Ejection; Stellar Spectra; X Ray Astronomy; Astrophysics; Black Holes:Spectroscopic Binaries; Mass Loss:Spectroscopic Binaries; Masses:Spectroscopic Binaries full text sources ADS | data products SIMBAD (9)

The binary pulsar - Physical processes, possible companions, and evolutionary histories

A study of some aspects of the binary pulsar, PSR 1913+16, is presented in the light of recently reported observational results. If the companion to the pulsar gives a Newtonian contribution to the observed apsidal motion (a helium star or a rotating white dwarf), then it will probably be observable: the former either optically or through the dispersive effects of a stellar wind, and the latter through a secular change in the observed inclination of the orbit. If alternatively the companion behaves dynamically as a point mass (apsidal motion caused solely by general relativity), observations of the O (..nu../c)/sup 2/ frequency shift will furnish a measurement of the masses of the components. In addition, with a tenfold improvement in timing accuracy, the post-Newtonian corrections to the Keplerian ellipse and the effects of aberration could in principle be measured. This would then provide a determination of the orientation of the pulsar spin axis and allow the observation of geodetic spin precession to become a test of general relativity. We also examine the test based on the detection of orbital period changes due to gravitational radiation.Possible evolutionary histories are discussed. The most probable present system consists of two neutron stars, the endmore » result of an X-ray binary phase followed by a double core star phase. In this scenario the long timing age and short period of PSR 1913+16 are shown to be interrelated if the pulsar was the first neutron star formed. To show that other companions are not ruled out on evolutionary grounds, we construct alternate histories leading to either He star, white dwarf, or black hole companions. (AIP)« less