Summary of IAU Colloquium 191: The Environment and Evolution Binary and Multiple Stars (original) (raw)

On the binary properties and the spatial and kinematical distribution of young stars

Monthly Notices of the Royal Astronomical Society, 1998

The effects which star cluster concentration and binarity have on observable parameters, that characterise the dynamical state of a population of stars after their birth aggregate dissolves, are investigated. To this end, the correlations between ejection velocity, binary proportion, mean system mass, binary orbital period and mass ratio are quantified for simulated aggregates. These consist of a few hundred low-mass binary and single stars, and have half-mass radii in the range 2.5 to 0.08 pc. The primordial binary-star population has a period distribution similar to that observed in Taurus-Auriga for pre-main sequence binaries. The findings presented here are useful for interpreting correlations between relative locations and proper motions, binary properties and masses of young stellar systems within and surrounding star forming regions, and of stellar systems escaping from Galactic clusters.

The Evolution of Compact Binary Star Systems

Living Reviews in Relativity, 2006

We review the formation and evolution of compact binary stars consisting of white dwarfs (WDs), neutron stars (NSs), and black holes (BHs). Binary NSs and BHs are thought to be the primary astrophysical sources of gravitational waves (GWs) within the frequency band of ground-based detectors, while compact binaries of WDs are important sources of GWs at lower frequencies to be covered by space interferometers (LISA). Major uncertainties in the current understanding of properties of NSs and BHs most relevant to the GW studies are discussed, including the treatment of the natal kicks which compact stellar remnants acquire during the core collapse of massive stars and the common envelope phase of binary evolution. We discuss the coalescence rates of binary NSs and BHs and prospects for their detections, the formation and evolution of binary WDs and their observational manifestations. Special attention is given to AM CVn-stars -compact binaries in which the Roche lobe is filled by another WD or a low-mass partially degenerate helium-star, as these stars are thought to be the best LISA verification binary GW sources.

Chapter 1 STELLAR AND DYNAMICAL EVOLUTION WITHIN TRIPLE STARS

2016

About 5-15% of stellar systems are at least triple. About 1% of systems with a primary of > 1 M are triple with a longer period that is less than 30y, and so may in principle be capable of Roche-lobe over ow in both the inner and the outer orbits, at di erent times. We discuss possible evolutionary paths for these systems, some of which may lead to objects that are di cult to understand in the context of purely binary evolution. An example is OW Gem, a binary containing two supergiants (spectral types F and G) with masses that di fer by a factor of 1.5. There is also a triple-star pathway which could lead rather naturally to low-mass X-ray binaries; whereas binary pathways often appear rather contrived. We also discuss some dynamical processes involved in the 3-body problem. A number of triple stars are found in clusters. Similar systems can be created by gravitational capture during N-body simulations of Galactic clusters, especially if there is an assumed primordial binary population. We discuss the properties of these triples, and note that many can be quite long-lived.

Binary Stars in Young Clusters - a Theoretical Perspective

Proceedings of the International Astronomical Union

The preponderance of binary systems in all known stellar populations makes them exciting dynamical agents for research on topics as varied as star formation, star-cluster dynamics and the interiors of young and old stars. Today we know that the Galactic-field binary population is probably a dynamically evolved version of the Taurus-Auriga pre-main sequence population, and that the initial distributions of binarystar orbital elements are probably universal. Furthermore, N -body calculations tentatively suggest that OB stars form in energetic binaries near cluster cores, and that binaries with 'forbidden' orbital elements that are produced in stellar encounters, may turn out to be very useful windows into stellar interiors, potentially allowing tests of pre-main sequence evolution theory as well as of models of main-sequence stars.

The Multiplicity of the Hyades and Its Implications for Binary Star Formation and Evolution

The Astronomical Journal, 1998

A 2.2 µm speckle imaging survey of 167 bright (K < 8.5 mag) Hyades members reveals a total of 33 binaries with separations spanning 0. ′′ 044 to 1. ′′ 34 and magnitude differences as large as 5.5 mag. Of these binaries, 13 are new detections and an additional 17 are now spatially resolved spectroscopic binaries, providing a sample from which dynamical masses and distances can be obtained. The closest 3 systems, marginally resolved at Palomar, were re-observed with the 10m Keck telescope in order to determine accurate binary star parameters. Combining the results of this survey with previous radial velocity, optical speckle, and direct imaging Hyades surveys, the detected multiplicity of the sample is: 98 singles, 59 binaries, and 10 triples.

Multiple Stars and Stellar Evolution

2010

We discuss the incidence of multiplity, particularly among the bright and therefore relatively thoroughly examined stars, and note certain types of (a) binary stars that might be expected to merge, and (b) single stars with characteristics that suggest they may be former binaries that merged. Some Be stars and rapidly rotating red giants seem like possible merger products; and perhaps even some magnetic peculiar stars that are rapidly rotating.