Nonlinear Outcome of Gravitational Instability in Cooling, Gaseous Disks

Gammie, Charles F.

doi:10.1086/320631

Cited by 979 publications

(1,726 citation statements)

References 49 publications

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“…Spiral structures start appearing at Q ∼ 1.7, while fragmentation occurs for Q ∼ 1 (Durisen et al 2007;Helled et al 2013). When this stage is reached, turbulence and shocks are expected to develop, providing a heating mechanism that may compensate for the cooling of the disk (Gammie 2001). We can therefore estimate the sound speed at the stage of fragmentation via…”

Section: Planet Formation Via Gravitational Instabilitiesmentioning

confidence: 99%

Planet formation from the ejecta of common envelopes

Schleicher

Dreizler

2014

A&A

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Context. The close binary system NN Serpentis must have gone through a common envelope phase before the formation of its white dwarf. During this phase, a substantial amount of mass was lost from the envelope. The recently detected orbits of circumbinary planets are probably inconsistent with planet formation before the mass loss. Aims. We explore whether new planets may have formed from the ejecta of the common envelope and derive the expected planetary mass as a function of radius. Methods. We employed the Kashi & Soker model to estimate the amount of mass that is retained during the ejection event and inferred the properties of the resulting disk from the conservation of mass and angular momentum. The resulting planetary masses were estimated from models with and without radiative feedback. Results. We show that the observed planetary masses can be reproduced for appropriate model parameters. Photoheating can stabilize the disks in the interior, potentially explaining the observed planetary orbits on scales of a few AU. We compare the expected mass scale of planets for 11 additional systems with observational results and find hints of two populations, one consistent with planet formation from the ejecta of common envelopes and the other a separate population that may have formed earlier.Conclusions. The formation of the observed planets from the ejecta of common envelopes seems feasible. The model proposed here can be tested through refined observations of additional post-common envelope systems. While it appears observationally challenging to distinguish between the accretion on pre-existing planets and their growth from new fragments, it may be possible to further constrain the properties of the protoplanetary disk through additional observations of current planetary candidates and post-common envelope binary systems.

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Section: Planet Formation Via Gravitational Instabilitiesmentioning

confidence: 99%

Planet formation from the ejecta of common envelopes

Schleicher

Dreizler

2014

A&A

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“…M d is much smaller than the black hole mass so that the disk is not globally self-gravitating (i.e., in the radial direction; Shlosman & Begelman 1989) and will not gravitationally influence stellar dynamics in Sgr A * . The disk is locally (vertically) self-gravitating when -Bell 1965;Kolykhalov & Sunyaev 1980;Gammie 2001). We have…”

Section: Mass Of the Disk And Maximum Densitymentioning

confidence: 99%

X-ray flares from Sgr A^*: Star-disk interactions?

Nayakshin

Cuadra

Sunyaev

2003

A&A

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Abstract. Sgr A * , the putative black hole in our Galactic Center (GC), is extraordinary dim in all frequencies. Apparently the black hole is unable to accrete at the Bondi accretion rate for some reason. Another mystery of Sgr A * is the recently discovered large magnitude and short duration X-ray flares (Baganoff et al. 2001). Here we point out that X-ray flares should be expected from star passages through an inactive (i.e. formerly accreting) disk. There are thousands of stars in Sgr A * stellar cluster, and each star will pass through the disk twice per orbit. A shock hot enough to emit X-rays is formed around the star when the latter is inside the disk. We develop a simple yet somewhat detailed model for the X-ray emission from the shock. The duration of the flares, their X-ray spectra, frequency of events, and weakness of emission in the radio and near infra-red appear to be consistent with the available observations of X-ray flares. We therefore suggest that at least a fraction of the observed flares is due to the star-disk passages. Such star-disk flares are also of interest in the nuclei of nearby inactive galaxies, especially in connection with perspective Constellation-X and XEUS X-ray missions.

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“…Stamatellos et al 2007;Forgan et al 2009), or choosing a parametrized cooling law in order to mimic expected scaling relations (e.g. Gammie 2001). The former method was used by Bonnell & Rice (2008), but the accuracy of the Stamatellos et al (2007) scheme has recently been challenged by Wilkins & Clarke (2012).…”

Section: Coolingmentioning

confidence: 99%

“…Such simulations typically find that there is a critical value β crit ∼ 5 which marks the "fragmentation boundary". For slower cooling (β > β crit ), gravitational instability results in self-regulating spiral density waves which transport angular momentum through the disc, while faster cooling (β < β crit ) results in gravitational fragmentation into bound clumps (Gammie 2001 (Lodato & Clarke 2011;Paardekooper et al 2011;Rice et al 2012), but the exact origin of the lack of convergence in scale-free simulations of self-gravitating discs remains uncertain However, a parametrization where cooling depends only on position is not appropriate for our infalling cloud calculations, so we instead choose a parametrization where the cooling rate depends on the local gas density ρ. We choose a scaling such that…”

Section: Coolingmentioning

confidence: 99%

Misaligned accretion on to supermassive black hole binaries

Dunhill

Alexander

Nixon

et al. 2014

Monthly Notices of the Royal Astronomical Society

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We present the results of high-resolution numerical simulations of gas clouds falling onto binary supermassive black holes to form circumbinary accretion discs, with both prograde and retrograde cloud orbits. We explore a range of clouds masses and cooling rates. We find that for low mass discs that cool fast enough to fragment, prograde discs are significantly shorter-lived than similar discs orbiting retrograde with respect to the binary. For fragmenting discs of all masses, we also find that prograde discs fragment across a narrower radial region. If the cooling is slow enough that the disc enters a self-regulating gravitoturbulent regime, we find that alignment between the disc and binary planes occurs on a timescale primarily dictated by the disc thickness. We estimate realistic cooling times for such discs, and find that in the majority of cases we expect fragmentation to occur. The longer lifetime of lowmass fragmenting retrograde discs allows them to drive significant binary evolution, and may provide a mechanism for solving the 'last parsec problem'.

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Nonlinear Outcome of Gravitational Instability in Cooling, Gaseous Disks

Cited by 979 publications

References 49 publications

Planet formation from the ejecta of common envelopes

Planet formation from the ejecta of common envelopes

X-ray flares from Sgr A^*: Star-disk interactions?

Misaligned accretion on to supermassive black hole binaries

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Nonlinear Outcome of Gravitational Instability in Cooling, Gaseous Disks

Cited by 979 publications

References 49 publications

Planet formation from the ejecta of common envelopes

Planet formation from the ejecta of common envelopes

X-ray flares from Sgr A*: Star-disk interactions?

Misaligned accretion on to supermassive black hole binaries

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Product

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X-ray flares from Sgr A^*: Star-disk interactions?