A model of a spheroidal body

Bonnor, W. B.

doi:10.1088/0264-9381/15/2/009

Cited by 106 publications

(177 citation statements)

References 21 publications

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“…The typical observed core is centrally condensed, so its free-fall time increases with radius. If a core has a well-defined mass boundary, as in the model of a pressure-truncated isothermal sphere (Bonnor 1956;Ebert 1955), the free-fall time at the boundary sets the maximum duration of accretion. But this maximum duration applies only if the collapse is not limited sooner, by environmental and dynamical processes discussed above.…”

Section: Core Boundariesmentioning

confidence: 99%

Star Formation in Dense Clusters

Myers

2011

ApJ

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A model of core-clump accretion with equally likely stopping describes star formation in the dense parts of clusters, where models of isolated collapsing cores may not apply. Each core accretes at a constant rate onto its protostar, while the surrounding clump gas accretes as a power of protostar mass. Short accretion flows resemble Shu accretion and make low-mass stars. Long flows resemble reduced Bondi accretion and make massive stars. Accretion stops due to environmental processes of dynamical ejection, gravitational competition, and gas dispersal by stellar feedback, independent of initial core structure. The model matches the field star initial mass function (IMF) from 0.01 to more than 10 solar masses. The core accretion rate and the mean accretion duration set the peak of the IMF, independent of the local Jeans mass. Massive protostars require the longest accretion durations, up to 0.5 Myr. The maximum protostar luminosity in a cluster indicates the mass and age of its oldest protostar. The distribution of protostar luminosities matches those in active star-forming regions if protostars have a constant birthrate but not if their births are coeval. For constant birthrate, the ratio of young stellar objects to protostars indicates the star-forming age of a cluster, typically ∼1 Myr. The protostar accretion luminosity is typically less than its steady spherical value by a factor of ∼2, consistent with models of episodic disk accretion.

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Section: Core Boundariesmentioning

confidence: 99%

Star Formation in Dense Clusters

Myers

2011

ApJ

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“…Isothermal, hydrostatic spheres with density contrasts between cloud core and cloud edge below 14.5 are stable against gravitational contraction (first shown by Bonnor (1956) and Ebert 1955). This simple stability condition can be cast in terms of a critical mass (M BE ), similar to the Jeans mass (M J ) but with a slightly different numerical coefficient (e.g., for the critical BE sphere, M BE 2 M J of a uniform, isothermal sphere of equal temperature and external pressure).…”

Section: Introductionmentioning

confidence: 95%

On the Role of Ambient Environments in the Collapse of Bonnor-Ebert Spheres

Kaminski

Frank

Carroll

et al. 2014

ApJ

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We consider the interaction between a marginally stable Bonnor-Ebert (BE) sphere and the surrounding ambient medium. In particular, we explore how the infall from an evolving ambient medium can trigger the collapse of the sphere using three-dimensional adaptive mesh refinement simulations. We find the resulting collapse dynamics to vary considerably with ambient density. In the highest ambient density cases, infalling material drives a strong compression wave into the cloud. It is the propagation of this wave through the cloud interior that triggers the subsequent collapse. For lower ambient densities, we find the main trigger of collapse to be a quasistatic adjustment of the BE sphere to gravitational settling of the ambient gas. In all cases, we find that the classic "outside-in" collapse mode for super-critical BE spheres is recovered before a protostar (i.e., sink particle) forms. Our work supports scenarios in which BE dynamics naturally begins with either a compression wave or infall dominated phase, and only later assumes the usual outside-in collapse behavior.

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“…Static bodies made of electrically counterpoised dust-in the terminology of Bonnor (see, e.g., [27])-offer simple, physically not unrealistic, models to discuss, for example, large redshifts [27], the hoop conjecture [28], or the linear dragging of inertial frames [29]. Their global spacetimes can be covered in both exterior and interior regions by harmonic coordinates X, Y, Z in which the metric takes the form…”

Section: Spacetimes Of Electrically Counterpoised Dustmentioning

confidence: 99%

On the uniqueness of harmonic coordinates

Bičák

Katz

2005

Czech J Phys

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Harmonic coordinate conditions in stationary asymptotically flat spacetimes with matter sources have more than one solution. The solutions depend on the degree of smoothness of the metric and its first derivatives, which we wish to impose across the material boundary, and on the conditions at infinity and at a suitable point inside the matter. This is illustrated in detail by simple fully solvable examples of static spherically symmetric spacetimes in global harmonic coordinates. Examples of stationary electrovacuum spacetimes described simply in harmonic coordinates are also given. They can represent the exterior fields of material discs.The use of an appropriate background metric considerably simplifies the calculations.

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A model of a spheroidal body

Cited by 106 publications

References 21 publications

Star Formation in Dense Clusters

Star Formation in Dense Clusters

On the Role of Ambient Environments in the Collapse of Bonnor-Ebert Spheres

On the uniqueness of harmonic coordinates

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