Visual Binaries in the Orion Nebula Cluster

Reipurth, Bo; Guimarães, M. M.; Connelley, Michael S.; Bally, John

doi:10.1086/523596

Cited by 126 publications

(256 citation statements)

References 60 publications

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“…A flat binary period distribution has not only been observed in Sco OB II but also in other regions (e.g. Connelley et al 2008;Reipurth et al 2007) and has been used in several theoretical studies involving the evolution of primordial binary frequencies (Heggie & Aarseth 1992;Ivanova et al 2005;Hurley et al 2007). …”

Section: Methods and Cluster Setupmentioning

confidence: 99%

Evolution of the binary population in young dense star clusters

Kaczmarek

Olczak

Pfalzner

2011

A&A

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Context. Field stars are not always single stars, but can often be found in bound double systems. Since binary frequencies in the birth places of stars, young embedded clusters, are sometimes even higher than on average the question arises of how binary stars form in young dense star clusters and how their properties evolve to those observed in the field population. Aims. We assess, the influence of stellar dynamical interactions on the primordial binary population in young dense cluster environments. Methods. We perform numerical N-body simulations of the Orion nebula cluster like star cluster models including primordial binary populations using the simulation code nbody6 ++ . Results. We find two remarkable results that have yet not been reported: The first is that the evolution of the binary frequency in young dense star clusters is independent predictably of its initial value. The time evolution of the normalized number of binary systems has a fundamental shape. The second main result is that the mass of the primary star is of vital importance to the evolution of the binary. The more massive a primary star, the lower the probability that the binary is destroyed by gravitational interactions. This results in a higher binary frequency for stars more massive than 2 M compared to the binary frequency of lower mass stars. The observed increase in the binary frequency with primary mass is therefore most likely not due to differences in the formation process but can be entirely explained as a dynamical effect. Conclusions. Our results allow us to draw conclusions about the past and the future number of binary systems in young dense star clusters and demonstrate that the present field stellar population has been influenced significantly by its natal environments.

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Section: Methods and Cluster Setupmentioning

confidence: 99%

Evolution of the binary population in young dense star clusters

Kaczmarek

Olczak

Pfalzner

2011

A&A

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“…The high-mass population exhibits a higher binary frequency than the low-mass primaries (Preibisch et al 1999;Schertl et al 2003;Köhler et al 2006). For the ONC, we use the study of Reipurth et al (2007), who find 75 binaries and 3 triples among 781 ONC members. In the limited range from 67.5 to 675 AU, this corresponds to a binary fraction of 8.8 ± 1.1 percent after correcting for contamination.…”

Section: Orion Nebula Clustermentioning

confidence: 99%

“…For instance, the Taurus star-formation region, which is about 1 Myr old, has a very low density (1−10 stars pc −3 ) and a binary population which has about twice the frequency (Ghez et al 1993;Leinert et al 1993;Simon et al 1995;Kohler & Leinert 1998;Kraus & Hillenbrand 2009) of that for solar-type main sequence stars in the Galactic field (the canonical sample used here for comparison, Duquennoy & Mayor 1991). On the other hand, the similarly aged Orion Nebula Cluster has a much higher density (2×10 4 stars pc −3 ) and its binary fraction is smaller than that in the field (Reipurth et al 2007). The density of IC 348 is comparable to that of NGC 2024, but the former is 3−5 times older.…”

Section: Introductionmentioning

confidence: 97%

Inverse dynamical population synthesis

Marks

Kroupa

2012

A&A

253

302

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Binary populations in young star clusters show multiplicity fractions both lower and up to twice as high as those observed in the Galactic field. We follow the evolution of a population of binary stars in dense and loose star clusters starting with an invariant initial binary population and a formal multiplicity fraction of unity, and demonstrate that these models can explain the observed binary properties in Taurus, ρ Ophiuchus, Chamaeleon, Orion, IC 348, Upper Scorpius A, Praesepe, and the Pleiades. The model needs to consider solely different birth densities for these regions. The evolved theoretical orbital-parameter distributions are highly probable parent distributions for the observed ones. We constrain the birth conditions (stellar mass, M ecl , and half-mass radius, r h ) for the derived progenitors of the star clusters and the overall present-day binary fractions allowed by the present model. The results compare very well with properties of molecular cloud clumps on the verge of star formation. Combining these with previously and independently obtained constraints on the birth densities of globular clusters, we identify a weak stellar mass -half-mass radius correlation for cluster-forming cloud clumps, r h /pc ∝ (M ecl /M ) 0.13 ± 0.04 . The ability of the model to reproduce the binary properties in all the investigated young objects, covering present-day densities from 1−10 stars pc −3 (Taurus) to 2 × 10 4 stars pc −3 (Orion), suggests that environment-dependent dynamical evolution plays an important role in shaping the present-day properties of binary populations in star clusters, and that the initial binary properties may not vary dramatically between different environments.

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“…It is probably a typical star-forming region and has the advantage that many parameters of both the cluster structure and the binary population have been well-observed (e.g. Jones & Walker 1988;Prosser et al 1994;Hillenbrand 1997;Hillenbrand & Hartmann 1998;O'Dell et al 2009;Preibisch et al 1999;Köhler et al 2006;Reipurth et al 2007). The ONC's radial density profile declines in its outer parts as ρ present ∝ r −2 (Jones & Walker 1988;Hillenbrand 1997) and is much flatter (ρ core ∝ r −0.5 ) within R core ≈ 0.2 pc.…”

Section: Cluster Setupmentioning

confidence: 99%

Towards the field binary population: influence of orbital decay on close binaries

Korntreff

Kaczmarek

Pfalzner

2012

A&A

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Context. Surveys of binary populations in the solar neighbourhood have discovered that the periods of G-and M-type stars are log-normally distributed in the range 0.1−10 11 days. However, observations of young binary populations in various star-forming regions have instead inferred a log-uniform distribution. Some process(es) must clearly be responsible for this change in the period distribution over time. Most stars form in star clusters, so it is here that the(se) process(es) take place. Aims. In dense young clusters, two important dynamical processes occur: i) the gas-induced orbital decay of embedded binary systems and ii) the destruction of soft binaries in three-body interactions. The emphasis in this work is on orbital decay as its influence on the binary distribution in clustered environments has largely been neglected so far. Methods. We performed Monte Carlo simulations of binary populations to model the process of orbital decay due to friction between the gas and binary stars. In addition, the destruction of soft binaries in young dense star clusters was simulated using N-body modelling of binary populations. Results. It is known that the cluster dynamics destroy the number of wide binaries, but leave short-period binaries basically undisturbed. Here we demonstrate that this result is also valid for an initially log-uniform period binary distribution. In contrast, the process of orbital decay significantly reduces the number and changes the properties of short-period binaries, leaving wide binaries largely uneffected. Until now, it has been unclear whether the short period distribution of the field has remained unaltered since its formation. We show here, that if any alteration took place, then orbital decay is a prime candidate for this task. In combination, the dynamics of these two processes, convert even an initial log-uniform distribution into a log-normal period distribution. The probability is 94% that the evolved period distribution and the observed period distribution have been sampled from the same parent distribution. Conclusions. Our results provide a new picture for the development of the field binary population: binaries can be formed as a result of the star-formation process in star clusters with periods that are sampled from the log-uniform distribution. As the cluster evolves, short-period binaries merge to form single stars by means of gas-induced orbital decay, while the dynamical evolution in the cluster destroys wide binaries. The combination of these two equally important processes reshapes an initial log-uniform period distribution to the log-normal period distribution that is observed in the field.

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Visual Binaries in the Orion Nebula Cluster

Cited by 126 publications

References 60 publications

Evolution of the binary population in young dense star clusters

Evolution of the binary population in young dense star clusters

Inverse dynamical population synthesis

Towards the field binary population: influence of orbital decay on close binaries

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