Double or binary: on the multiplicity of open star clusters

Marcos, R. de la Fuente; Marcos, C. de la Fuente

doi:10.1051/0004-6361/200912297

Cited by 56 publications

(29 citation statements)

References 27 publications

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“…The similarity of their age in DAML, log(age) = 7.507 and 7.78, respectively, makes the physical binarity plausible. The space separations for these three pairs have to be compared to the typical value of 10 pc of the binary candidates proposed by de La Fuente Marcos & de La Fuente Marcos (2009). Table 4 gives the list of the pairs that differ by less than 200 pc in distance and 5 km s −1 in velocity in our high-quality sample.…”

Section: Peculiar Open Clusters Pairs and Groupsmentioning

confidence: 99%

Open cluster kinematics with Gaia DR2

Soubiran

Cantat-Gaudin

Romero-Gómez

et al. 2018

A&A

184

189

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Context. Open clusters are very good tracers of the evolution of the Galactic disc. Thanks to Gaia, their kinematics can be investigated with an unprecedented precision and accuracy. Aims. The distribution of open clusters in the 6D phase space is revisited with Gaia DR2. Methods. The weighted mean radial velocity of open clusters was determined, using the most probable members available from a previous astrometric investigation that also provided mean parallaxes and proper motions. Those parameters, all derived from Gaia DR2 only, were combined to provide the 6D phase-space information of 861 clusters. The velocity distribution of nearby clusters was investigated, as well as the spatial and velocity distributions of the whole sample as a function of age. A high-quality subsample was used to investigate some possible pairs and groups of clusters sharing the same Galactic position and velocity. Results. For the high-quality sample of 406 clusters, the median uncertainty of the weighted mean radial velocity is 0.5 km s −1 . The accuracy, assessed by comparison to ground-based high-resolution spectroscopy, is better than 1 km s −1 . Open clusters nicely follow the velocity distribution of field stars in the close solar neighbourhood as previously revealed by Gaia DR2. As expected, the vertical distribution of young clusters is very flat, but the novelty is the high precision to which this can be seen. The dispersion of vertical velocities of young clusters is at the level of 5 km s −1 . Clusters older than 1 Gyr span distances to the Galactic plane of up to 1 kpc with a vertical velocity dispersion of 14 km s −1 , typical of the thin disc. Five pairs of clusters and one group with five members might be physically related. Other binary candidates that have been identified previously are found to be chance alignments. ABSTRACTContext. N/A Aims. N/A Methods. N/A Results. N/A

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Section: Peculiar Open Clusters Pairs and Groupsmentioning

confidence: 99%

Open cluster kinematics with Gaia DR2

Soubiran

Cantat-Gaudin

Romero-Gómez

et al. 2018

A&A

184

189

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“…Binary clusters are systematically younger than single clusters e.g. half of the clusters in binaries identified by De La Fuente Marcos & de La Fuente Marcos (2009) are < 25 Myr old, and almost all of those are in coeval pairs (see also Dieball et al 2002;Palma et al 2016). This is not an unusual E-mail: rjarnold1@sheffield.ac.uk † Royal Society Dorothy Hodgkin Fellow result; the clusters that constitute a binary are often coeval (e.g.…”

Section: Introductionmentioning

confidence: 99%

How do binary clusters form?

Arnold¹,

Goodwin²,

Griffiths³

et al. 2017

Monthly Notices of the Royal Astronomical Society

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Approximately 10 per cent of star clusters are found in pairs, known as binary clusters. We propose a mechanism for binary cluster formation; we use N-body simulations to show that velocity substructure in a single (even fairly smooth) region can cause binary clusters to form. This process is highly stochastic and it is not obvious from a region's initial conditions whether a binary will form and, if it does, which stars will end up in which cluster. We find the probability that a region will divide is mainly determined by its virial ratio, and a virial ratio above 'equilibrium' is generally necessary for binary formation. We also find that the mass ratio of the two clusters is strongly influenced by the initial degree of spatial substructure in the region.

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“…The question of the possible existence of a sizeable fraction of candidate binary clusters in the Galactic disk has been revisited again by de la Fuente Marcos & de la Fuente Marcos (2009b). Using complete, volume-limited samples, they have found consistent and statistically robust figures: at the Solar Circle, at least 12% of all open clusters could be part of potential binary systems.…”

Section: Introductionmentioning

confidence: 99%

The Evolution of Primordial Binary Open Star Clusters: Mergers, Shredded Secondaries, and Separated Twins

Marcos

2010

ApJ

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The properties of the candidate binary star cluster population in the Magellanic Clouds and Milky Way are similar. The fraction of candidate binaries is ∼10% and the pair separation histogram exhibits a bimodal distribution commonly attributed to their transient nature. However, if primordial pairs cannot survive for long as recognizable bound systems, how are they ending up? Here, we use simulations to confirm that merging, extreme tidal distortion, and ionization are possible depending on the initial orbital elements and mass ratio of the cluster pair. Merging is observed for initially close pairs but also for wider systems in nearly parabolic orbits. Its characteristic timescale depends on the initial orbital semi-major axis, eccentricity, and cluster pair mass ratio, becoming shorter for closer, more eccentric equal mass pairs. Shredding of the less massive cluster and subsequent separation is observed in all pairs with appreciably different masses. Wide pairs evolve into separated twins characterized by the presence of tidal bridges and separations of 200-500 pc after one Galactic orbit. Most observed binary candidates appear to be following this evolutionary path which translates into the dominant peak (25-30 pc) in the observed pair separation distribution. The secondary peak at smaller separations (10-15 pc) can be explained as due to close pairs in almost circular orbits and/or undergoing merging. Merged clusters exhibit both peculiar radial density and velocity dispersion profiles shaped by synchronization and gravogyro instabilities. Simulations and observations show that long-term binary open cluster stability is unlikely.

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Double or binary: on the multiplicity of open star clusters

Cited by 56 publications

References 27 publications

Open cluster kinematics with Gaia DR2

Open cluster kinematics with Gaia DR2

How do binary clusters form?

The Evolution of Primordial Binary Open Star Clusters: Mergers, Shredded Secondaries, and Separated Twins

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