The Origin of Binary Stars

Tohline, J. E.

doi:10.1146/annurev.astro.40.060401.093810

Cited by 172 publications

(189 citation statements)

References 129 publications

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“…The condensations can grow in mass through (competitive) accretion from the parent core. In general, core fragmentation is believed to be the principal mechanism for the formation of binary and multiple stellar systems (e.g., Tohline 2002;Goodwin et al 2007).…”

Section: Deuterated Formaldehydementioning

confidence: 99%

A (sub)millimetre study of dense cores in Orion B9

Miettinen

Harju

Haikala

et al. 2012

A&A

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Context. Studies of dense molecular-cloud cores at (sub)millimetre wavelengths are needed to understand the early stages of star formation. Aims. We aim to further constrain the properties and evolutionary stages of dense cores in Orion B9. The prime objective of this study is to examine the dust emission of the cores near the peak of their spectral energy distributions, and to determine the degrees of CO depletion, deuterium fractionation, and ionisation. Methods. The central part of Orion B9 was mapped at 350 μm with APEX/SABOCA. A sample of nine cores in the region were observed in C 17 O(2−1), H 13 CO + (4−3) (towards 3 sources), DCO + (4−3), N 2 H + (3−2), and N 2 D + (3−2) with APEX/SHFI. These data are used in conjunction with our previous APEX/LABOCA 870-μm dust continuum data. Results. All the LABOCA cores in the region covered by our SABOCA map were detected at 350 μm. The strongest 350 μm emission is seen towards the Class 0 candidate SMM 3. Many of the LABOCA cores show evidence of substructure in the higher-resolution SABOCA image. In particular, we report on the discovery of multiple very low-mass condensations in the prestellar core SMM 6. Based on the 350-to-870 μm flux density ratios, we determine dust temperatures of T dust 7.9−10.8 K, and dust emissivity indices of β ∼ 0.5−1.8. The CO depletion factors are in the range f D ∼ 1.6−10.8. The degree of deuteration in N 2 H + is 0.04−0.99, where the highest value (seen towards the prestellar core SMM 1) is, to our knowledge, the most extreme level of N 2 H + deuteration reported so far. The level of HCO + deuteration is about 1-2%. The fractional ionisation and cosmic-ray ionisation rate of H 2 could be determined only towards two sources with the lower limits of ∼2−6 × 10 −8 and ∼2.6 × 10 −17 −4.8 × 10 −16 s −1 , respectively. We also detected D 2 CO towards two sources. Conclusions. The detected protostellar cores are classified as Class 0 objects, in agreement with our previous SED results. The detection of subcondensations within SMM 6 shows that core fragmentation can already take place during the prestellar phase. The origin of this substructure is likely caused by thermal Jeans fragmentation of the elongated parent core. Varying levels of f D and deuteration among the cores suggest that they are evolving chemically at different rates. A low f D value and the presence of gas-phase D 2 CO in SMM 1 suggest that the core chemistry is affected by the nearby outflow. The very high N 2 H + deuteration in SMM 1 is likely to be remnant of the earlier CO-depleted phase.

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Section: Deuterated Formaldehydementioning

confidence: 99%

A (sub)millimetre study of dense cores in Orion B9

Miettinen

Harju

Haikala

et al. 2012

A&A

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“…Tohline 2002). While most solar-type (0.5 ≤ M ≤ 2 M ) pre-main sequence (PMS) stars are observed to be in binary systems with typical separations ∼10−300 AU (e.g., Duchêne et al 2004Duchêne et al , 2007, see also below), the detailed manner in which individual prestellar cores fragment (or not) during collapse to form multiple (or Based on observations carried out with the IRAM Plateau de Bure Interferometer.…”

Section: Introductionmentioning

confidence: 99%

Toward understanding the formation of multiple systems

Maury¹,

André²,

Hennebelle

et al. 2010

A&A

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Context. The formation process of binary stars and multiple systems is poorly understood. The multiplicity rate of Class II premain-sequence stars and Class I protostars is well documented and known to be high (∼ 30% to 50% between ∼100 and 4000 AU). However, optical / near-infrared observations of Class I/Class II YSOs barely constrain the pristine properties of multiple systems, since dynamical evolution can quickly alter these properties during the protostellar phase. Aims. Here, we seek to determine the typical outcome of protostellar collapse and to constrain models of binary formation by core fragmentation during collapse, using high-resolution millimeter continuum imaging of very young (Class 0) protostars observed at the beginning of the main accretion phase. Methods. We carried out a pilot high-resolution study of 5 Class 0 objects, including 3 Taurus sources and 2 Perseus sources, using the most extended (A) configuration of the IRAM Plateau de Bure Interferometer (PdBI) at 1.3 mm. Our PdBI observations have a typical HPBW resolution ∼0.3 −0.5 and rms continuum sensitivity ∼0.1−1 mJy/beam, which allow us to probe the multiplicity of Class 0 protostars down to separations a ∼ 50 AU and circumstellar mass ratios q ∼ 0.07. Results. We detected all 5 primary Class 0 sources in the 1.3 mm dust continuum. A single component associated with the primary Class 0 object was detected in the case of the three Taurus sources, while robust evidence of secondary components was found toward the two Perseus sources: L1448-C and NGC1333-IR2A. We show that the secondary 1.3 mm continuum component detected ∼600 AU south-east of L1448-C, at a position angle close to that of the CO(2−1) jet axis traced by our data, is an outflow feature directly associated with the powerful jet driven by L1448-C. The secondary 1.3 mm continuum component detected ∼1900 AU southeast of NGC1333-IR2A may either be a genuine protostellar companion or trace the edge of an outflow cavity. Therefore, our PdBI observations revealed only wide (>1500 AU) protobinary systems and/or outflow-generated features. Conclusions. When combined with previous millimeter interferometric observations of Class 0 protostars, our pilot PdBI study tentatively suggests that the binary fraction in the ∼75−1000 AU range increases from the Class 0 to the Class I stage. It also seems to argue against purely hydrodynamic models of binary star formation. We briefly discuss possible alternative scenarios to reconcile the low multiplicity rate of Class 0 protostars on small scales with the higher binary fraction observed at later (e.g. Class I) evolutionary stages.

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“…Astrometric measurements of orbital motion can determine the inclination, and thus the mass ratio. Obtaining a large number of systems with well-determined q values helps to refine our knowledge of the binary population (Tohline 2002;Goodwin 2013) and SB1s with astrometric orbits (e.g. Pourbaix & Jorissen 2000;Jancart et al 2005;Ren & Fu 2013) can complement the samples of doublelined spectroscopic binaries (SB2, e.g.…”

Section: Introductionmentioning

confidence: 99%

Astrometric mass ratios for three spectroscopic binaries

Fekel

2013

A&A

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The orbits of five single-lined spectroscopic binaries have recently been determined. We now use astrometric measurements that were collected with the H satellite to constrain the systems' mass ratios and secondary masses. The barycentric astrometric orbits of three binary systems, HD 140667, HD 158222, and HD 217924, are fully determined and precise estimates of their mass ratios are obtained. Follow-up of these systems with infrared spectroscopy could yield model-independent dynamical masses for all components.

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The Origin of Binary Stars

Cited by 172 publications

References 129 publications

A (sub)millimetre study of dense cores in Orion B9

A (sub)millimetre study of dense cores in Orion B9

Toward understanding the formation of multiple systems

Astrometric mass ratios for three spectroscopic binaries

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