scholarly journals Migration jumps of planets in transition discs

2020 ◽  
Vol 643 ◽  
pp. A87
Author(s):  
Thomas Rometsch ◽  
Peter J. Rodenkirch ◽  
Wilhelm Kley ◽  
Cornelis P. Dullemond
Keyword(s):  
Equations Of State ◽  
Accretion Rate ◽  
Dynamical Evolution ◽  
Central Star ◽  
Dynamical Behaviour ◽  
High Mass ◽  
Outer Planet ◽  
Mass Accretion Rate ◽  
Wide Transition ◽  
Outward Migration

Context. Transition discs form a special class of protoplanetary discs that are characterised by a deficiency of disc material close to the star. In a subgroup, inner holes in these discs can stretch out to a few tens of au while there is still mass accretion onto the central star observed at the same time. Aims. We analyse the proposition that this type of wide transition disc is generated by the interaction of the disc with a system of embedded planets. Methods. We performed two-dimensional hydrodynamics simulations of a flat disc. Different equations of state were used including locally isothermal models and more realistic cases that consider viscous heating, radiative cooling, and stellar heating. Two massive planets (with masses of between three and nine Jupiter masses) were embedded in the disc and their dynamical evolution due to disc–planet interaction was followed for over 100 000 yr. The simulations account for mass accretion onto the star and planets. We included models with parameters reminiscent of the system PDS 70. To assess the observability of features in our models we performed synthetic ALMA observations. Results. For systems with a more massive inner planet, there are phases where both planets migrate outward engaged in a 2:1 mean motion resonance via the Masset-Snellgrove mechanism. In sufficiently massive discs, the resulting formation of a vortex and the interaction with it can trigger rapid outward migration of the outer planet where its distance can increase by tens of au in a few thousand years. After another few thousand years, the outer planet rapidly migrates back inwards into resonance with the inner planet. We call this emerging composite phenomenon a migration jump. Outward migration and the migration jumps are accompanied by a high mass accretion rate onto the star. The synthetic images reveal numerous substructures depending on the type of dynamical behaviour. Conclusions. Our results suggest that the outward migration of two embedded planets is a prime candidate for the explanation of the observed high stellar mass accretion rate in wide transition discs. The models for PDS 70 indicate it is not currently undergoing a migration jump but might very well be in a phase of outward migration.

scholarly journals Matter accretion onto a conformal gravity black hole

2020 ◽  
Vol 80 (12) ◽  
Author(s):  
G. Abbas ◽  
A. Ditta
Keyword(s):  
Black Hole ◽  
Equations Of State ◽  
Accretion Rate ◽  
Black Hole Mass ◽  
Conformal Gravity ◽  
De Sitter ◽  
Schwarzschild Black Hole ◽  
Mass Rate ◽  
Mass Accretion Rate ◽  
The Impact

AbstractThe accretion of test fluids flowing onto a black hole is investigated. Particularly, by adopting a dynamical Hamiltonian approach, we are capable to find the critical points for various cases of black hole in conformal gravity. In these cases, we have analyzed the general solutions of accretion employing the isothermal equations of state. The steady state and spherically symmetric accretion of different test fluids onto the conformal gravity black hole has been considered. Further, we have classified these flows in the context of equations of state and the cases of conformal gravity black hole. The new behavior of polytropic fluid accretion is also discussed in all three cases of black hole. Black hole mass accretion rate is the most important part of this research in which we have investigated that the Schwarzschild black hole produce a typical signature than the conformal gravity black hole and Schwarzschild–de Sitter black hole. The critical fluid flow and the mass accretion rate have been presented graphically by the impact parameters $$\beta $$ β , $$\gamma $$ γ , k and these parameters have great significance. Additionally, the maximum mass rate of accretion fall near the universal and Killing horizons and minimum rate of accretion occurs in between these regions. Finally, the results are compared with the different cases of black hole available in the literature.

Characteristics of transonic spherical symmetric accretion flow in Schwarzschild-de Sitter and Schwarzschild anti-de Sitter backgrounds, in pseudo-general relativistic paradigm

2015 ◽  
Vol 24 (11) ◽  
pp. 1550084 ◽  
Author(s):  
Shubhrangshu Ghosh ◽  
Prabir Banik
Keyword(s):  
Cosmological Constant ◽  
Accretion Rate ◽  
High Mass ◽  
Complete Analysis ◽  
De Sitter ◽  
Accretion Flow ◽  
Mass Accretion Rate ◽  
Cd Galaxies ◽  
General Relativistic ◽  
Limiting Value

In this paper, we present a complete work on steady state spherically symmetric Bondi type accretion flow in the presence of cosmological constant (Λ) in both Schwarzschild-de Sitter (SDS) and Schwarzschild anti-de Sitter (SADS) backgrounds considering an isolated supermassive black hole (SMBH), with the inclusion of a simple radiative transfer scheme, in the pseudo-general relativistic paradigm. We do an extensive analysis on the transonic behavior of the Bondi type accretion flow onto the cosmological BHs including a complete analysis of the global parameter space and the stability of flow, and do a complete study of the global family of solutions for a generic polytropic flow. Bondi type accretion flow in SADS background renders multiplicity in its transonic behavior with inner "saddle" type and outer "center" type sonic points, with the transonic solutions forming closed loops or contours. There is always a limiting value for ∣Λ∣ up to which we obtain valid stationary transonic solutions, which correspond to both SDS and SADS geometries; this limiting value moderately increases with the increasing radiative efficiency of the flow, especially correspond to Bondi type accretion flow in SADS background. Repulsive Λ suppresses the Bondi accretion rate by an order of magnitude for relativistic Bondi type accretion flow for a certain range in temperature, and with a marginal increase in the Bondi accretion rate if the corresponding accretion flow occurs in SADS background. However, for a strongly radiative Bondi type accretion flow with high mass accretion rate, the presence of cosmological constant do not much influence the corresponding Bondi accretion rate of the flow. Our analysis show that the relic cosmological constant has a substantial effect on Bondi type accretion flow onto isolated SMBHs and their transonic solutions beyond length-scale of kiloparsecs, especially if the Bondi type accretion occurs onto the host supergiant ellipticals or central dominant (CD) galaxies directly from ambient intercluster medium (ICM). However, for high mass accretion rate, the influence of cosmological constant on Bondi accretion dynamics, generically, diminishes. As active galactic nuclei (AGN)/ICM feedback can be advertently linked to Bondi type spherical accretion, any proper modeling of AGN feedback or megaparsecs-scale jet dynamics or accretion flow from ICM onto the central regions of host galaxies should take into account the relevant information of repulsive Λ, especially in context to supergiant elliptical galaxies or CD galaxies present in rich galaxy clusters. This could also explore the feasibility to limit the value of Λ, from the kinematics in local galactic-scales.

scholarly journals An alternative approach to the relation between accretion luminosity and mass accretion rate

2021 ◽  
Author(s):  
Stefano Pezzuto
Keyword(s):  
Radiation Pressure ◽  
Accretion Rate ◽  
Free Fall ◽  
High Mass ◽  
Alternative Form ◽  
Mass Star ◽  
Practical Applications ◽  
Mass Accretion Rate ◽  
Alternative Approach ◽  
Accretion Rates

Abstract In this paper I introduce and discuss an alternative approach to the relation between accretion luminosity, Lacc, and mass accretion rate, ˙M : instead of the universally adopted Lacc = GM ˙M/R, I propose the dynamical definition Lacc = v2f˙M/2 where vf is the final velocity of the infalling matter at the surface of the accreting object of mass M and radius R. Both definitions are based on the energy conservation, but while the former assumes that matter is in free fall, the latter is valid always. By adopting the alternative form for Lacc, I show that the Eddington luminosity Led, when the outward radiation pressure wins on gravity, is never produced with a finite ˙M. Instead, Led is a limit asymptotically reached when ˙M → ¥. My argument is very simple, so I felt the need to find a possible explanation to why no one arrived to this conclusion before. To this aim, I give a brief presentation of the history of accretion, from the pioneer work of Hoyle and collaborators until the ’60s of last century, to show how the perception of the role of the radiation pressure in accretion evolved. I give also some practical applications of the formulae I derived, in the case of high-mass star formation and of the growth of super massive black holes. The study of these two processes, already complex per se, becomes more difficult to solve because of the existence of a limiting ˙M, named Eddington mass accretion rate or ˙Med, that it is supposed to generate a luminosity equal to Led, making it impossible to accrete at rate ˙M > ˙Med. Accretion rates higher than ˙Med are however necessary, as theory and observations show. My definition of Lacc takes naturally into account the work done by radiation pressure to slow down the infalling matter: as a consequence, Lacc does not increase linearly with ˙M and Led is only an asymptotic value.

scholarly journals X-shooter survey of disk accretion in Upper Scorpius

2020 ◽  
Vol 639 ◽  
pp. A58 ◽  
Author(s):  
C. F. Manara ◽  
A. Natta ◽  
G. P. Rosotti ◽  
J. M. Alcalá ◽  
B. Nisini ◽  
...  
Keyword(s):  
Accretion Rate ◽  
Protoplanetary Disks ◽  
Young Stellar Objects ◽  
High Mass ◽  
Star Forming ◽  
Mass Accretion Rate ◽  
Disk Mass ◽  
Accretion Rates ◽  
Disk Evolution ◽  
Simple Models

Determining the mechanisms that drive the evolution of protoplanetary disks is a necessary step toward understanding how planets form. For this work, we measured the mass accretion rate for young stellar objects with disks at age > 5 Myr, a critical test for the current models of disk evolution. We present the analysis of the spectra of 36 targets in the ∼5–10 Myr old Upper Scorpius star-forming region for which disk masses were measured with ALMA. We find that the mass accretion rates in this sample of old but still surviving disks are similarly high as those of the younger (∼1−3 Myr old) star-forming regions of Lupus and Chamaeleon I, when considering the dependence on stellar and disk mass. In particular, several disks show high mass accretion rates ≳10−9 M⊙ yr−1 while having low disk masses. Furthermore, the median values of the measured mass accretion rates in the disk mass ranges where our sample is complete at a level ∼60−80% are compatible in these three regions. At the same time, the spread of mass accretion rates at any given disk mass is still > 0.9 dex, even at age > 5 Myr. These results are in contrast with simple models of viscous evolution, which would predict that the values of the mass accretion rate diminish with time, and a tighter correlation with disk mass at age > 5 Myr. Similarly, simple models of internal photoevaporation cannot reproduce the observed mass accretion rates, while external photoevaporation might explain the low disk masses and high accretion rates. A possible partial solution to the discrepancy with the viscous models is that the gas-to-dust ratio of the disks at ∼5–10 Myr is significantly different and higher than the canonical 100, as suggested by some dust and gas disk evolution models. The results shown here require the presence of several interplaying processes, such as detailed dust evolution, external photoevaporation, and possibly MHD winds, to explain the secular evolution of protoplanetary disks.

scholarly journals On the emergent system mass function: the contest between accretion and fragmentation

2020 ◽  
Vol 500 (2) ◽  
pp. 1697-1707
Author(s):  
Paul C Clark ◽  
Anthony P Whitworth
Keyword(s):  
Star Formation ◽  
Standard Deviation ◽  
Mass Distribution ◽  
Power Law ◽  
Accretion Rate ◽  
Mass Function ◽  
High Mass ◽  
New Model ◽  
System Formation ◽  
Low Mass

ABSTRACT We propose a new model for the evolution of a star cluster’s system mass function (SMF). The model involves both turbulent fragmentation and competitive accretion. Turbulent fragmentation creates low-mass seed proto-systems (i.e. single and multiple protostars). Some of these low-mass seed proto-systems then grow by competitive accretion to produce the high-mass power-law tail of the SMF. Turbulent fragmentation is relatively inefficient, in the sense that the creation of low-mass seed proto-systems only consumes a fraction, ${\sim }23{{\ \rm per\ cent}}$ (at most ${\sim }50{{\ \rm per\ cent}}$), of the mass available for star formation. The remaining mass is consumed by competitive accretion. Provided the accretion rate on to a proto-system is approximately proportional to its mass (dm/dt ∝ m), the SMF develops a power-law tail at high masses with the Salpeter slope (∼−2.3). If the rate of supply of mass accelerates, the rate of proto-system formation also accelerates, as appears to be observed in many clusters. However, even if the rate of supply of mass decreases, or ceases and then resumes, the SMF evolves homologously, retaining the same overall shape, and the high-mass power-law tail simply extends to ever higher masses until the supply of gas runs out completely. The Chabrier SMF can be reproduced very accurately if the seed proto-systems have an approximately lognormal mass distribution with median mass ${\sim } 0.11 \, {\rm M}_{\odot }$ and logarithmic standard deviation $\sigma _{\log _{10}({M/M}_\odot)}\sim 0.47$).

scholarly journals Planetary embryo collisions and the wiggly nature of extreme debris discs

2021 ◽  
Vol 502 (2) ◽  
pp. 2984-3002
Author(s):  
Lewis Watt ◽  
Zoe Leinhardt ◽  
Kate Y L Su
Keyword(s):  
Equations Of State ◽  
Semimajor Axis ◽  
Central Star ◽  
Impact Angle ◽  
Narrow Region ◽  
Term Variation ◽  
Planetary Embryo ◽  
Smoothed Particle ◽  
Giant Impacts ◽  
Post Impact

ABSTRACT In this paper, we present results from a multistage numerical campaign to begin to explain and determine why extreme debris disc detections are rare, what types of impacts will result in extreme debris discs and what we can learn about the parameters of the collision from the extreme debris discs. We begin by simulating many giant impacts using a smoothed particle hydrodynamical code with tabulated equations of state and track the escaping vapour from the collision. Using an N-body code, we simulate the spatial evolution of the vapour generated dust post-impact. We show that impacts release vapour anisotropically not isotropically as has been assumed previously and that the distribution of the resulting generated dust is dependent on the mass ratio and impact angle of the collision. In addition, we show that the anisotropic distribution of post-collision dust can cause the formation or lack of formation of the short-term variation in flux depending on the orientation of the collision with respect to the orbit around the central star. Finally, our results suggest that there is a narrow region of semimajor axis where a vapour generated disc would be observable for any significant amount of time implying that giant impacts where most of the escaping mass is in vapour would not be observed often but this does not mean that the collisions are not occurring.

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