The formation of very wide binaries during the star cluster dissolution phase
By M. B. N. Kouwenhoven, S. Goodwin, R. Parker, M. B. Davies, D. Malmberg, Pavel Kroupa. 2010
176 citations recorded by the source corpus.
Over the past few decades, numerous wide (> 103 au) binaries in the Galactic field and halo have been discovered. Their existence cannot be explained by the process of star formation or by dynamical interactions in the field, and their origin has long been a mystery. We explain the origin of these wide binaries by formation during the dissolution phase of young star clusters: an initially unbound pair of stars may form a binary when their distance in phase space is small. Using N-body simulations, we find that the resulting wide binary fraction in the semimajor axis range 103 au < a < 0.1 pc for individual clusters is 1-30 per cent, depending on the initial conditions. The existence of numerous wide binaries in the field is consistent with observational evidence that most clusters start out with a large degree of substructure. The wide binary fraction decreases strongly with increasing cluster mass, and the semimajor axis of the newly formed binaries is determined by the initial cluster size. The resulting eccentricity distribution is thermal, and the mass ratio distribution is consistent with gravitationally focused random pairing. As a large fraction of the stars forms in primordial binaries, we predict that a large number of the observed 'wide binaries' are in fact triple or quadruple systems. By integrating over the initial cluster mass distribution, we predict a binary fraction of a few per cent in the semimajor axis range 103 au < a < 0.1 pc in the Galactic field, which is smaller than the observed wide binary fraction. However, this discrepancy may be solved when we consider a broad range of cluster morphologies. (Less)
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Citations in the corpus
- VERY WIDE BINARIES AND OTHER COMOVING STELLAR COMPANIONS: A BAYESIAN ANALYSIS OF THE HIPPARCOS CATALOGUE (2010, background): “We interpret this as evidence that very wide binaries are often found in hierarchical systems, as suggested by a number of authors (Makarov et al. 2008; Caballero 2009, 2010; Kouwenhoven et al. 2010).”
- PROSPECTING IN LATE-TYPE DWARFS: A CALIBRATION OF INFRARED AND VISIBLE SPECTROSCOPIC METALLICITIES OF LATE K AND M DWARFS SPANNING 1.5 dex (2012, background): “It is likely that most wide binaries form as higher order systems (Kouwenhoven et al. 2010).”
- Stellar Multiplicity (2013, background): “Alternatively, they may have formed from separate cores and have been ejected simultaneously from a cluster on sufficiently similar trajectories as to remain weakly bound (Kouwenhoven et al. 2010, Moeckel & Clarke 2011).”
- Mind Your Ps and Qs: The Interrelation between Period (P) and Mass-ratio (Q) Distributions of Binary Stars (2016, background): “Dynamical processing tends to eject the lower mass companions with q ≈ 0.1 - 0.3 due to their lower binding energies (Marks & Kroupa 2011; Kouwenhoven et al. 2010; Perets & Kouwenhoven 2012; Thies et al. 2015).”
- PLANET HUNTERS: A TRANSITING CIRCUMBINARY PLANET IN A QUADRUPLE STAR SYSTEM (2012, background): “This type of hierarchal system may be a natural outcome of the dynamics during the dissipation of embedded clusters (Kouwenhoven et al. 2010).”