Binary stars in the Orion Nebula Cluster

Köhler, Rainer H.; Petr-Gotzens, M. G.; McCaughrean, M. J.; Bouvier, J.; Duchêne, Gaspard; Quirrenbach, A.; Zinnecker, H.

doi:10.1051/0004-6361:20054561

Cited by 122 publications

(169 citation statements)

References 41 publications

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“…Nonetheless, for illustrative purposes we assume that the ONC has cluster age of 1 Myr Hillenbrand (1997) and obtain α(1 Myr) = 0.92 using the given fit. Assuming a present-day binary frequency of 60%, motivated by observations that find a consistency between the binary populations of field G dwarfs (Duquennoy & Mayor 1991) and the ONC (Petr et al 1998;Köhler et al 2006), we derive an initial binary frequency of 74%. This is clearly below the binary frequency observed in young sparse star-forming regions as Taurus-Auriga (Leinert et al 1993;Ghez et al 1993) and suggests that the initial binary frequency depends on the star-forming environment as stated by Durisen & Sterzik (1994).…”

Section: Resultsmentioning

confidence: 99%

“…Clearly, a larger fraction A144, page 6 of 8 of low-mass binaries is destroyed during the dynamical evolution of the cluster. The boundary of 2 M between high and low-mass primaries was chosen in accordance with the study of Köhler et al (2006), who performed a high spatial resolution infrared study of the binary population in the ONC. They found the frequency of binaries with high-mass primaries to be significantly higher.…”

Section: Resultsmentioning

confidence: 99%

“…However, observations of binary populations in star clusters do not provide such a clear picture as the observations of the field binary population. While in dense star clusters such as the Orion nebula cluster (ONC) or NGC 2024 the observed Article published by EDP Sciences A144, page 1 of 8 binary frequency is similar to the field binary frequency (Köhler et al 2006;Beck et al 2003), sparse clusters such as the TaurusAuriga association have much higher binary frequencies (see Duchêne 1999, and references therein). This leads to the question of what defines the binary frequency in the different environments.…”

Section: Introductionmentioning

confidence: 99%

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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: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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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.…”

Section: Orion Nebula Clustermentioning

confidence: 99%

Inverse dynamical population synthesis

Marks

Kroupa

2012

A&A

246

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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“…The B1 star NU Ori is known to have a spectroscopic companion with a period of 8 days (Morrell & Levato 1991) and a wide visual companion at a distance of 0.47 (Köhler et al 2006). Our AMBER observations from 31/12/2011 (see Fig.…”

Section: Nu Orimentioning

confidence: 99%

The multiplicity of massive stars in the Orion Nebula Cluster as seen with long-baseline interferometry

Grellmann

Preibisch

Ratzka

et al. 2013

A&A

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Context. The characterization of multiple stellar systems is an important ingredient for testing current star formation models. Stars are more often found in multiple systems, the more massive they are. A complete knowledge of the multiplicity of high-mass stars over the full range of orbit separations is thus essential to understand their still debated formation process. Aims. Infrared long baseline interferometry is very well suited to close the gap between spectroscopic and adaptive optics searches. Observations of the Orion Nebula Cluster (ONC) in general and the Trapezium Cluster in particular can help to answer the question about the origin and evolution of multiple stars. Earlier studies provide a good knowledge about the multiplicity of the stars at very small (spectroscopic companions) and large separations (AO, speckle companions) and thus make the ONC a good target for such a project. Methods. We used the near infrared interferometric instrument AMBER at ESOs Very Large Telescope Interferometer to observe a sample of bright stars in the ONC. We complement our data set by archival NACO observations of θ 1 Ori A to obtain more information about the orbit of the close visual companion. Results. Our observations resolve the known multiple systems θ 1 Ori C and θ 1 Ori A and provide new orbit points, which confirm the predicted orbit and the determined stellar parameters for θ 1 Ori C. Combining AMBER and NACO data for θ 1 Ori A we were able to follow the (orbital) motion of the companion from 2003 to 2011. We furthermore find hints for a companion around θ 1 Ori D, whose existence has been suggested already before, and a previously unknown companion to NU Ori. With a probability of ∼90% we can exclude further companions with masses of ≥3 M around our sample stars for separations between ∼2 mas and ∼110 mas. Conclusions. We conclude that the companion around θ 1 Ori A is most likely physically related to the primary star and not only a chance projected star. The newly discovered possible companions further increase the multiplicity in the ONC. For our sample of two O and three B-type stars we find on average 2.5 known companions per primary, which is around five times more than for low-mass stars.

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Binary stars in the Orion Nebula Cluster

Cited by 122 publications

References 41 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

The multiplicity of massive stars in the Orion Nebula Cluster as seen with long-baseline interferometry

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