Binary star formation: accretion-induced rotational fragmentation

Whitworth, Anthony Peter; Chapman, Sydney; Bhattal, A. S.; Disney, M. J.; Pongracic, H.; Turner, J. A.

doi:10.1093/mnras/277.2.727

Cited by 79 publications

(96 citation statements)

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“…We note that these levels of turbulence involve much lower non-thermal velocities than the earlier work of Whitworth et al (1995), Turner et al (1995), Whitworth et al (1996), Klein et al (2001Klein et al ( , 2003, Bate et al (2002aBate et al ( ,b, 2003, Bonnell et al (2003), Delgado-Donate (2003, 2004. Consequently they may be applicable to scenarios in which instability develops more quasistatically due to ambipolar diffusion; provided that some turbulence can persist through (or be regenerated after) the ambipolar diffusion phase, and provided the subsequent collapse is sufficiently rapid.…”

Section: Introductionmentioning

confidence: 49%

“…In our simulations, systems with high mass ratio tend to be close (all systems with q > 0.7, and most systems with q > 0.4, are binaries with a < 20 au), but the reverse is not always true: in other words, there are a few close binaries with low mass ratios. Close binaries are presumed to acquire high mass ratios because the material accreting onto the system has high specific angular momentum, and is therefore more readily accommodated by the secondary (Whitworth et al 1995;Bate & Bonnell 1997;Paper I). Figure 8 shows the CDF of eccentricity for all the simulations having α turb ≥ 0.05 and the linear fit to the observed distribution proposed by DM91.…”

Section: Mass Ratiosmentioning

confidence: 99%

“…7). Many of these systems with high mass-ratio arise because the binary system has accreted material with relatively high specific angular momentum, and this material can more easily be accommodated by the secondary (e.g., Whitworth et al 1995).…”

Section: Distribution Of Mass-ratiosmentioning

confidence: 99%

“…In the highly dynamic scenario the collapse of a prestellar core is far more likely to lead to fragmentation and the formation of multiple systems (e.g., Whitworth et al 1995;Turner et al 1995;Whitworth et al 1996;Klein et al 2001Klein et al , 2003Bate et al 2002aBate et al ,b, 2003Bonnell et al 2003;Delgado-Donate 2003, 2004Goodwin et al 2004a,b;Hennebelle et al 2003Hennebelle et al , 2004. This is because in the highly dynamic scenario prestellar cores are formed non-quasistatically and therefore (a) they are launched directly into the non-linear regime of gravitational collapse, and (b) they are likely to have retained some internal turbulence.…”

Section: Introductionmentioning

confidence: 99%

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Simulating star formation in molecular cores

Goodwin¹,

Whitworth²,

Ward-Thompson³

2004

A&A

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128

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Abstract. We explore, by means of a large ensemble of SPH simulations, how the level of turbulence affects the collapse and fragmentation of a star-forming core. All our simulated cores have the same mass (5.4 M ), the same initial density profile (chosen to fit observations of L1544), and the same barotropic equation of state, but we vary (a) the initial level of turbulence (as measured by the ratio of turbulent to gravitational energy, α turb ≡ U turb /|Ω| = 0, 0.01, 0.025, 0.05, 0.10 and 0.25) and (b), for fixed α turb , the details of the initial turbulent velocity field (so as to obtain good statistics).

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Section: Introductionmentioning

confidence: 49%

Section: Mass Ratiosmentioning

confidence: 99%

Section: Distribution Of Mass-ratiosmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Simulating star formation in molecular cores

Goodwin¹,

Whitworth²,

Ward-Thompson³

2004

A&A

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128

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“…In both cases, fragmentation is only the first step in binary formation and processes such as disk accretion and dynamical interactions all contribute to determine the final properties of binary systems (Bate 2004). In general, continued accretion onto both objects from a common reservoir tends in the long term to equalize the masses, moving the q distribution towards unity, and this effect seems to be more significant for high-mass primaries and in closer binaries (Whitworth et al 1995;Bate 2000). Recently, a variation on capture has been proposed as mechanism for forming wide binaries (Kouwenhoven et al 2010;Moeckel & Bate 2010).…”

Section: Introductionmentioning

confidence: 99%

Binary Formation Mechanisms: Constraints From the Companion Mass Ratio Distribution

Reggiani

Meyer

2011

ApJ

105

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We present a statistical comparison of the mass ratio distribution of companions, as observed in different multiplicity surveys, to the most recent estimate of the single-object mass function. The main goal of our analysis is to test whether or not the observed companion mass ratio distribution (CMRD) as a function of primary star mass and star formation environment is consistent with having been drawn from the field star initial mass function (IMF). We consider samples of companions for M dwarfs, solar-type stars, and intermediate-mass stars, both in the field as well as clusters or associations, and compare them with populations of binaries generated by random pairing from the assumed IMF for a fixed primary mass. With regard to the field we can reject the hypothesis that the CMRD was drawn from the IMF for different primary mass ranges: the observed CMRDs show a larger number of equal-mass systems than predicted by the IMF. This is in agreement with fragmentation theories of binary formation. For the open clusters α Persei and the Pleiades we also reject the IMF random-pairing hypothesis. Concerning young star-forming regions, currently we can rule out a connection between the CMRD and the field IMF in Taurus but not in Chamaeleon I. Larger and different samples are needed to better constrain the result as a function of the environment. We also consider other companion mass functions and we compare them with observations. Moreover the CMRD both in the field and clusters or associations appears to be independent of separation in the range covered by the observations. Combining therefore the CMRDs of M (1-2400 AU) and G (28-1590 AU) primaries in the field and intermediate-mass primary binaries in Sco OB2 (29-1612 AU) for mass ratios, q = M 2 /M 1 , from 0.2 to 1, we find that the best chi-square fit follows a power law dN/dq ∝ q β , with β = −0.50 ± 0.29, consistent with previous results. Finally, we note that the Kolmogorov-Smirnov test gives a ∼1% probability of the observed CMRD in the Pleiades and Taurus being consistent with that observed for solar-type primaries in the field over comparable primary mass range. This highlights the value of using CMRDs to understand which star formation events contribute most to the field.

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The formation of brown dwarfs

Whitworth¹,

Goodwin

2005

Astron Nachr

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We review four mechanisms for forming brown dwarfs: (i) turbulent fragmentation (producing very low-mass prestellar cores); (ii) gravitational instabilities in discs; (iii) dynamical ejection of stellar embryos from their placental cores; and (iv) photo-erosion of pre-existing cores in HII regions. We argue (a) that these are simply the mechanisms of low-mass star formation, and (b) that they are not mutually exclusive. If, as seems possible, all four mechanisms operate in nature, their relative importance may eventually be constrained by their ability to reproduce the binary statistics of brown dwarfs, but this will require fully 3-D radiative magneto-hydrodynamic simulations.Comment: 7 pages, 1 figure. To appear in Astron.Nachrichten. Includes an.cls fil

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Binary star formation: accretion-induced rotational fragmentation

Cited by 79 publications

References 0 publications

Simulating star formation in molecular cores

Simulating star formation in molecular cores

Binary Formation Mechanisms: Constraints From the Companion Mass Ratio Distribution

The formation of brown dwarfs

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