On the properties of young multiple stars

Delgado-Donate, Eduardo; Clarke, C. J.; Bate, Matthew R.; Hodgkin, S. T.

doi:10.1111/j.1365-2966.2004.07803.x

Cited by 117 publications

(152 citation statements)

References 74 publications

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“…Star-forming regions are generally too dispersed for binaries to be disrupted by interactions between members. The alternative is that many stars form not just in binaries but in unstable higher order multiples that get disrupted with time, as is indeed suggested by numerical simulations ( Bate et al 2002;Delgado-Donate et al 2004). For a recent review on the current status of the field, see Duchêne et al (2006).…”

Section: Introductionmentioning

confidence: 98%

“…It therefore is not clear from the wide binary statistics alone if sparse or dense star formation is the dominant mode -possibly both contribute equally. What is clear is that models of cluster formation and early evolution probably are essential to explain multiplicity properties (e.g., Kroupa 1995;Bate et al 2002;Delgado-Donate et al 2004;Goodwin et al 2006). …”

Section: Deficit Of Wide Binariesmentioning

confidence: 99%

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Deficit of Wide Binaries in the η Chamaeleontis Young Cluster

Brandeker

Jayawardhana

Khavari

et al. 2006

ApJ

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We have carried out a sensitive high-resolution imaging survey of stars in the young (6Y8 Myr), nearby (97 pc) compact cluster around Chamaeleontis to search for stellar and substellar companions. Our data were obtained using the NACO adaptive optics system on the ESO Very Large Telescope (VLT). Given its youth and proximity, any substellar companions are expected to be luminous, especially in the near-infrared, and thus easier to detect next to their parent stars. Here, we present VLT NACO adaptive optics imaging with companion detection limits for 17 Cha cluster members, and follow-up VLT ISAAC near-infrared spectroscopy for companion candidates. The widest binary detected is $0B2, corresponding to the projected separation 20 AU, despite our survey being sensitive down to substellar companions outside 0B3, and planetary-mass objects outside 0B5. This implies that the stellar companion probability outside 0B3 and the brown dwarf companion probability outside 0B5 are less than 0.16 with 95% confidence. We compare the wide binary frequency of Cha to that of the similarly aged TW Hydrae association and estimate the statistical likelihood that the wide binary probability is equal in both groups to be less than 2 ; 10 À4 . Even though the Cha cluster is relatively dense, stellar encounters in its present configuration cannot account for the relative deficit of wide binaries. We thus conclude that the difference in wide binary probability in these two groups provides strong evidence for multiplicity properties being dependent on environment. In two appendices we derive the projected separation probability distribution for binaries, used to constrain physical separations from observed projected separations, and summarize statistical tools useful for multiplicity studies.

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Section: Introductionmentioning

confidence: 98%

Section: Deficit Of Wide Binariesmentioning

confidence: 99%

Deficit of Wide Binaries in the η Chamaeleontis Young Cluster

Brandeker

Jayawardhana

Khavari

et al. 2006

ApJ

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“…The binary frequency is correlated with the stellar mass and is found to be higher the more massive the star is (Preibisch et al 2001;Delgado-Donate et al 2004;Bate 2009). Very recently, Chini et al (2012) found that more than 80% of the stars with a mass greater than 16 M form close binary systems and Sana et al (2012) found that over ∼70% of stars born as O-type star will interact with a companion.…”

Section: Introductionmentioning

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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“…Still, given the low mass of the parent core, the potential for accretion after the initial fragmentation is much smaller than for higher mass systems, so that the final mass ratio should remain closer to the initial one. In most simulations of core fragmentation and cluster formation, the fragments have commensurable mass (Delgado-Donate et al 2004;Goodwin et al 2004;Bate 2012), which is directly related to the Jeans mass. In cases where subsequent accretion is limited, one thus expects systems to maintain mass ratios 0.5, in broad agreement with the observed distributions in open clusters and star-forming regions.…”

Section: Missing Binaries Among Field Very Low-mass Objectsmentioning

confidence: 99%

Substellar multiplicity in the Hyades cluster

Duchêne

Bouvier

Moraux

et al. 2013

A&A

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Aims. We present the first high-angular resolution survey for multiple systems among very low-mass stars and brown dwarfs in the Hyades open cluster. Methods. Using the Keck II adaptive optics system, we observed a complete sample of 16 objects with estimated masses 0.1 M . Results. We have identified three close binaries with projected separation 0. 11, or 5 AU. A number of wide, mostly faint candidate companions are also detected in our images, most of which are revealed as unrelated background sources based on astrometric and/or photometric considerations. The derived multiplicity frequency, 19 +13 −6 % over the 2-350 AU range, and the rarity of systems wider than 10 AU are both consistent with observations of field very low-mass objects. In the limited 3-50 AU separation range, the companion frequency is essentially constant from brown dwarfs to solar-type stars in the Hyades cluster, which is also in line with our current knowledge for field stars. Combining the binaries discovered in this surveys with those already known in the Pleiades cluster reveals that very low-mass binaries in open clusters, as well as in star-forming regions, are skewed toward lower mass ratios (0.6 q 0.8) than are their field counterparts, a result that cannot be accounted for by selection effects. Although the possibility of severe systematic errors in model-based mass estimates for very low-mass stars cannot be completely excluded, it is unlikely to explain this difference. Conclusions. We speculate that this trend indicates that surveys among very low-mass field stars may have missed a substantial population of intermediate mass ratio systems, implying that these systems are more common and more diverse than previously thought.

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On the properties of young multiple stars

Cited by 117 publications

References 74 publications

Deficit of Wide Binaries in the η Chamaeleontis Young Cluster

Deficit of Wide Binaries in the η Chamaeleontis Young Cluster

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

Substellar multiplicity in the Hyades cluster

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