Compact Triples Research Articles

TIC 290061484: A Triply Eclipsing Triple System with the Shortest Known Outer Period of 24.5 Days

We have discovered a triply eclipsing triple-star system, TIC 290061484, with the shortest known outer period, P out, of only 24.5 days. This “eclipses” the previous record set by λ Tauri at 33.02 days, which held for 68 yr. The inner binary, with an orbital period of P in = 1.8 days, produces primary and secondary eclipses and exhibits prominent eclipse timing variations with the same periodicity as the outer orbit. The tertiary star eclipses, and is eclipsed by, the inner binary with pronounced asymmetric profiles. The inclinations of both orbits evolve on observable timescales such that the third-body eclipses exhibit dramatic depth variations in TESS data. A photodynamical model provides a complete solution for all orbital and physical parameters of the triple system, showing that the three stars have masses of 6.85, 6.11, and 7.90 M ⊙, radii near those corresponding to the main sequence, and T eff in the range of 21,000–23,700 K. Remarkably, the model shows that the triple is in fact a subsystem of a hierarchical 2+1+1 quadruple with a distant fourth star. The outermost star has a period of ∼3200 days and a mass comparable to the stars in the inner triple. In ∼20 Myr, all three components of the triple subsystem will merge, undergo a Type II supernova explosion, and leave a single remnant neutron star. At the time of writing, TIC 290061484 is the most compact triple system and one of the tighter known compact triples (i.e., P out/P in = 13.7).

Von Zeipel – Lidov – Kozai cycles in action: Kepler triples with eclipse depth variations: KICs 6964043, 5653126, 5731312, and 8023317

ABSTRACT We report the results of the photodynamical analyses of four compact, tight triple stellar systems, KICs 6964043, 5653126, 5731312, and 8023317, based largely on Kepler and TESS data. All systems display remarkable eclipse timing and eclipse depth variations, the latter implying a non-aligned outer orbit. Moreover, KIC 6964043 is also a triply eclipsing system. We combined photometry, ETV curves, and archival spectral energy distribution data to obtain the astrophysical parameters of the constituent stars and the orbital elements with substantial precision. KICs 6964043 and 5653126 were found to be nearly flat with mutual inclinations imut = 4${_{.}^{\circ}}$1 and 12${_{.}^{\circ}}$3, respectively, while KICs 5731312 and 8023317 (imut = 39${_{.}^{\circ}}$4 and 55${_{.}^{\circ}}$7, respectively) are found to lie in the high imut regime of the von Zeipel-Kozai-Lidov (ZKL) theorem. We show that, currently, both high inclination triples exhibit observable unusual retrograde apsidal motion. Moreover, the eclipses will disappear in all but one of the four systems within a few decades. Short-term numerical integrations of the dynamical evolution reveal that both high inclination triples are currently subject to ongoing, large amplitude (Δe ∼ 0.3) inner eccentricity variations on centuries-long time-scales, in accord with the ZKL theorem. Longer-term integrations predict that two of the four systems may become dynamically unstable on ∼ Gyr time-scales, while in the other two triples common envelope phases and stellar mergers may occur. Finally, we investigate the dynamical properties of a sample of 71 KIC/TIC triples statistically, and find that the mutual inclinations and outer mass ratios are anticorrelated at the 4σ level. We discuss the implications for the formation mechanisms of compact triples.

The eccentricity distribution of wide binaries and their individual measurements

ABSTRACT Eccentricity of wide binaries is difficult to measure due to their long orbital periods. With Gaia’s high-precision astrometric measurements, eccentricity of a wide binary can be constrained by the angle between the separation vector and the relative velocity vector (the v-r angle). In this paper, by using the v-r angles of wide binaries in Gaia Early Data Release 3, we develop a Bayesian approach to measure the eccentricity distribution as a function of binary separations. Furthermore, we infer the eccentricities of individual wide binaries and make them publicly available. Our results show that the eccentricity distribution of wide binaries at 102 AU is close to uniform and becomes superthermal at >103 AU, suggesting two formation mechanisms dominating at different separation regimes. The close binary formation, most likely disc fragmentation, results in a uniform eccentricity distribution at <102 AU. The wide binary formation that leads to highly eccentric wide binaries at >103 AU may be turbulent fragmentation and/or the dynamical unfolding of compact triples. With Gaia, measuring eccentricities is now possible for a large number of wide binaries, opening a new window to understanding binary formation and evolution.

Properties of von Zeipel–Lidov–Kozai oscillations in triple systems at the quadrupole order: relaxing the test particle approximation

ABSTRACT Von Zeipel–Lidov–Kozai (ZLK) oscillations in hierarchical triple systems have important astrophysical implications such as triggering strong interactions and producing, e.g. Type Ia supernovae and gravitational wave sources. When considering analytic properties of ZLK oscillations at the lowest (quadrupole) expansion order, as well as complications due to higher order terms, one usually assumes the test particle limit, in which one of the bodies in the inner binary is massless. Although this approximation holds well for, e.g. planetary systems, it is less accurate for systems with more comparable masses such as stellar triples. Although non-test-particle effects are usually taken into account in numerical simulations, a more analytic approach focusing on the differences between the test particle and general case (at quadrupole order) has, to our knowledge, not been presented. Here, we derive several analytic properties of secular oscillations in triples at the quadruple expansion order. The latter applies even to relatively compact triples, as long as the inner bodies are similar in mass such that octupole-order effects are suppressed. We consider general conditions for the character of the oscillations (circular versus librating), minimum and maximum eccentricities, and time-scales, all as a function of $\gamma \equiv (1/2) \, L_1/G_2$, a ratio of inner-to-outer orbital angular momenta variables (γ = 0 in the test particle limit). In particular, eccentricity oscillations are more effective at retrograde orientations for non-zero γ; assuming zero initial inner eccentricity, the maximum eccentricity peaks at $\cos (i_{\mathrm{rel},0}) = -\gamma$, where $i_{\mathrm{rel},0}$ is the initial relative inclination. We provide a python script that can be used to quickly compute these properties.

Formation of close binaries by disc fragmentation and migration, and its statistical modelling

ABSTRACT Joint statistics of periods and mass ratios of close binaries and its dependence on primary mass can be explained by assuming that seed binary companions are formed by disc fragmentation at random intervals during assemblage of stellar mass and migrate inwards as they accrete from the circumbinary disc. A toy model based on simple prescriptions for the companion growth and migration reproduces such aspects of close solar-mass binaries as the distribution of binary periods P, the brown dwarf desert at short P, the nearly uniform distribution of mass ratios, and a population of equal-mass binaries (twins) that decreases linearly in frequency with log P. For massive stars, the model predicts a large fraction of early mergers, a distribution of log P with a negative slope, and a mass-ratio distribution that is also uniform but with a substantially reduced twin fraction. By treating disc fragmentation as a stochastic process, we also reproduce the observed properties of compact triples. Success of our toy model suggests that most close binaries and compact triples indeed formed by disc fragmentation followed by accretion-driven inward migration.

New inclination changing eclipsing binaries in the Magellanic Clouds

Context. Multiple stellar systems are unique laboratories for astrophysics. Analysis of their orbital dynamics, if well characterized from their observations, may reveal invaluable information about the physical properties of the participating stars. Unfortunately, there are only a few known and well described multiple systems, this is even more so for systems located outside the Milky Way galaxy. A particularly interesting situation occurs when the inner binary in a compact triple system is eclipsing. This is because the stellar interaction, typically resulting in precession of orbital planes, may be observable as a variation of depth of the eclipses on a long timescale. Aims. We aim to present a novel method to determine compact triples using publicly available photometric data from large surveys. Here we apply it to eclipsing binaries (EBs) in Magellanic Clouds from OGLE III database. Our tool consists of identifying the cases where the orbital plane of EB evolves in accord with expectations from the interaction with a third star. Methods. We analyzed light curves (LCs) of 26121 LMC and 6138 SMC EBs with the goal to identify those for which the orbital inclination varies in time. Archival LCs of the selected systems, when complemented by our own observations with Danish 1.54-m telescope, were thoroughly analyzed using the PHOEBE program. This provided physical parameters of components of each system. Time dependence of the EB’s inclination was described using the theory of orbital-plane precession. By observing the parameter-dependence of the precession rate, we were able to constrain the third companion mass and its orbital period around EB. Results. We identified 58 candidates of new compact triples in Magellanic Clouds. This is the largest published sample of such systems so far. Eight of them were analyzed thoroughly and physical parameters of inner binary were determined together with an estimation of basic characteristics of the third star. Prior to our work, only one such system was well characterized outside the Milky Way galaxy. Therefore, we increased this sample in a significant way. These data may provide important clues about stellar formation mechanisms for objects with different metalicity than found in our galactic neighborhood.

Dynamical formation and scattering of hierarchical triples: cross-sections, Kozai–Lidov oscillations, and collisions

Dynamical scattering of binaries and triple systems of stars, planets, and compact objects may produce highly inclined triple systems subject to Kozai-Lidov (KL) oscillations, potentially leading to collisions, mergers, Type Ia supernovae, and other phenomena. We present the results of more than 400 million gravitational scattering experiments of binary-binary, triple-single, and triple-binary scattering. We compute the cross sections for all possible outcomes and explore their dependencies on incoming velocity, mass, semi-major axis, and eccentricity, including analytic fits and discussion of the velocity dependence. For the production of new triple systems by scattering we find that compact triples are preferred, with ratios of outer to inner semi-major axes of ~few--100, flat or quasi-thermal eccentricity distributions, and flat distributions in cosine of the mutual inclination. Dynamically formed triples are thus subject to strong KL oscillations, the "eccentric Kozai mechanism," and non-secular effects. For single and binary flyby encounters with triple systems, we compute the cumulative cross section for changes to the mutual inclination, eccentricity, and semi-major axis ratio. We apply these results to scattering events in the field, open clusters, and globular clusters, and explore the implications for Type Ia supernovae via collisions and mergers, stellar collisions, and the lifetime and dynamical isolation of triple systems undergoing KL oscillations. An Appendix provides an analysis of the velocity dependence of the collision cross section in binary-single scattering.

Evolution of binaries with compact objects in globular clusters

AbstractDynamical interactions that take place between objects in dense stellar systems lead to frequent formation of exotic stellar objects, unusual binaries, and systems of higher multiplicity. They are most important for the formation of binaries with neutron stars and black holes, which are usually observationally revealed in mass-transferring binaries. Here we review the current understanding of compact object's retention, of the metallicity dependence on the formation of low-mass X-ray binaries with neutron stars, and how mass-transferring binaries with a black hole and a white dwarf can be formed. We discuss as well one old unsolved puzzle and two new puzzles posed by recent observations: what descendants do ultra-compact X-ray binaries produce, how are very compact triples formed, and how can black hole low-mass X-ray binaries acquire non-degenerate companions?

Formation and Evolution of Hierarchical Systems

AbstractInitial distributions of primordial binaries used in realisticN-body simulations give rise to bound subsystems of different multiplicity. An examination of the formation process shows that the most compact triples arise via binary-binary collisions, whereas higher-order systems have diverse origins. Low formation rates are compensated by long life-times, leading to a significant population building up. Being fairly energetic, the outer orbit tends to shrink by further encounters. In addition, external perturbations also modify the eccentricity and may create conditions for instability. Onecharacteristic outcome is internal disruption by the sling-shot mechanism. Such interactions are often sufficiently energetic to produce high-velocityescapers and it is not uncommon for triples and quadruples to be ejected. For high inclinations, the eccentricity growth induced by the Kozai effect may lead to significant shrinkage of the inner binary orbit by tidal circularization. If some of the components were spit into a dynamically inactive ultra-hard binary, the hierarchies would be attributed an even higher multiplicity. One implication of these results is that a proportion of multiple systems observed in the field may have been formed in a dynamical environment.

The compact triples 0710 + 439 and 2352 + 495 - A new morphology of radio galaxy nuclei

view Abstract Citations (48) References (67) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Compact Triples 0710+439 and 2352+495: A New Morphology of Radio Galaxy Nuclei Conway, J. E. ; Pearson, T. J. ; Readhead, A. C. S. ; Unwin, S. C. ; Xu, W. ; Mutel, R. L. Abstract The compact radio sources 0710+439 and 2352+495 have each been mapped using intercontinental VLBI arrays at frequencies of 5.0 and 10.7 GHz. The source 0710+439 has also been mapped at 1.7 GHz. Both sources consist of three principal components that lie almost on a straight line. Except for the existence of three VLBI components instead of two they both seem to have similar properties to members of the compact double class. Multi- epoch observations show that apparent velocities between the components in both sources are below c. In the source 0710+439 comparison of multi- epoch data allows us to set a limit of 0.054+/-0.14 h^-1^ c on the rate of separation of the two brightest components. In 2352+495 the multi- epoch 5 GHz VLBI data show that the flux density variations detected by total flux density monitoring are due to changes within the middle component. These fluctuations may be due to refractive interstellar scintillation or they may be intrinsic to the source; in either case the middle component must contain the most compact structure within the source. The morphology, spectra and variability of the middle components strongly suggest that the center of activity in both sources lies here rather than in either of the outer components, providing the first clear evidence of symmetric radio structure in a powerful active galaxy nucleus. Publication: The Astrophysical Journal Pub Date: September 1992 DOI: 10.1086/171697 Bibcode: 1992ApJ...396...62C Keywords: Active Galactic Nuclei; Active Galaxies; Galactic Structure; Radio Galaxies; Very Long Base Interferometry; Radio Sources (Astronomy); Radio Spectra; Astrophysics; GALAXIES: ACTIVE; GALAXIES: INDIVIDUAL ALPHANUMERIC: 0710; 439; GALAXIES: INDIVIDUAL ALPHANUMERIC: 2352; 495; GALAXIES: NUCLEI; RADIO CONTINUUM: GALAXIES; TECHNIQUES: INTERFEROMETRIC full text sources ADS | data products SIMBAD (10) NED (1)