scholarly journals Massive discs around low-mass stars

2020 ◽  
Vol 494 (3) ◽  
pp. 4130-4148 ◽  
Author(s):  
Thomas J Haworth ◽  
James Cadman ◽  
Farzana Meru ◽  
Cassandra Hall ◽  
Emma Albertini ◽  
...  
Keyword(s):  
Thermal Evolution ◽  
Solar Mass ◽  
Low Mass Stars ◽  
Star Mass ◽  
Smoothed Particle ◽  
Low Mass ◽  
Self Gravity ◽  
Stellar Masses ◽  
Smoothed Particle Hydrodynamic

ABSTRACT We use a suite of smoothed particle hydrodynamic simulations to investigate the susceptibility of protoplanetary discs to the effects of self-gravity as a function of star–disc properties. We also include passive irradiation from the host star using different models for the stellar luminosities. The critical disc-to-star mass ratio for axisymmetry (for which we produce criteria) increases significantly for low-mass stars. This could have important consequences for increasing the potential mass reservoir in a proto Trappist-1 system, since even the efficient Ormel et al. formation model will be influenced by processes like external photoevaporation, which can rapidly and dramatically deplete the dust reservoir. The aforementioned scaling of the critical Md/M* for axisymmetry occurs in part because the Toomre Q parameter has a linear dependence on surface density (which promotes instability) and only an $M_*^{1/2}$ dependence on shear (which reduces instability), but also occurs because, for a given Md/M*, the thermal evolution depends on the host star mass. The early phase stellar irradiation of the disc (for which the luminosity is much higher than at the zero age main sequence, particularly at low stellar masses) can also play a key role in significantly reducing the role of self-gravity, meaning that even solar mass stars could support axisymmetric discs a factor two higher in mass than usually considered possible. We apply our criteria to the DSHARP discs with spirals, finding that self-gravity can explain the observed spirals so long as the discs are optically thick to the host star irradiation.

scholarly journals The Role of Discs in the Collapse and Fragmentation of Prestellar Cores

2016 ◽  
Vol 33 ◽  
Author(s):  
O. Lomax ◽  
A. P. Whitworth ◽  
D. A. Hubber
Keyword(s):  
Kinetic Energy ◽  
Smoothed Particle Hydrodynamics ◽  
Low Mass Stars ◽  
Gravitational Instabilities ◽  
Disc Material ◽  
Prestellar Cores ◽  
Particle Hydrodynamics ◽  
Smoothed Particle ◽  
Low Mass

AbstractDisc fragmentation provides an important mechanism for producing low-mass stars in prestellar cores. Here, we describe smoothed particle hydrodynamics simulations which show how populations of prestellar cores evolve into stars. We find the observed masses and multiplicities of stars can be recovered under certain conditions.First, protostellar feedback from a star must be episodic. The continuous accretion of disc material on to a central protostar results in local temperatures which are too high for disc fragmentation. If, however, the accretion occurs in intense outbursts, separated by a downtime of ~ 104yr, gravitational instabilities can develop and the disc can fragment.Second, a significant amount of the cores’ internal kinetic energy should be in solenoidal turbulent modes. Cores with less than a third of their kinetic energy in solenoidal modes have insufficient angular momentum to form fragmenting discs. In the absence of discs, cores can fragment but results in a top-heavy distribution of masses with very few low-mass objects.

scholarly journals Rotational properties of the Orion nebular cluster revised

2006 ◽  
Vol 2 (S239) ◽  
pp. 311-313
Author(s):  
Natália R. Landin ◽  
Paolo Ventura ◽  
Francesca D'Antona ◽  
Luiz T. S. Mendes ◽  
Luiz P. R. Vaz
Keyword(s):  
Boundary Conditions ◽  
Observational Data ◽  
Main Sequence ◽  
Orion Nebula ◽  
Low Mass Stars ◽  
Physical Constraints ◽  
Rotational Evolution ◽  
Low Mass ◽  
Stellar Masses

AbstractThe observational data of the Orion Nebula Cluster (ONC) is reanalyzed by means of new sets of pre-main sequence (PMS) evolutionary tracks including rotation, non-gray boundary conditions (BC's) and either low (LCE) or high convection efficiency (HCE), aiming better understanding of the appropriate physical constraints for the rotational evolution of the stars within the ONC. The role played by convection is a key aspect of our analysis, since there are conflicting results from theory and observations. We derived stellar masses and ages for the ONC by using both LCE and HCE and considered was the role of non-gray atmospheres. Our results show that the resulting mass distribution for the bulk of the ONC population is in the range 0.2-0.4M⊙ for our non-gray models, and in the range 0.1-0.3M⊙ for gray models. In agreement with previous works, we found that a large percentage (∼70%) of low-mass stars (M≤Mtr, where Mtr is a transition mass) in the ONC appears to be fast rotators (P<4days). Mtr depends on the model choosen, being Mtr=0.5 for LCE, Mtr=0.35 for HCE and, as found in previous works, Mtr=0.25 for gray models. Finally, our analysis indicates that a second parameter is needed for a proper description of convection in the PMS phase.

scholarly journals Fragmentation favoured in discs around higher mass stars

2020 ◽  
Vol 492 (4) ◽  
pp. 5041-5051 ◽  
Author(s):  
James Cadman ◽  
Ken Rice ◽  
Cassandra Hall ◽  
Thomas J Haworth ◽  
Beth Biller
Keyword(s):  
Gravitational Instability ◽  
High Mass ◽  
Low Mass Stars ◽  
Star Mass ◽  
Gravitational Instabilities ◽  
Mass Ratios ◽  
Particle Hydrodynamics ◽  
Low Mass ◽  
M Stars ◽  
Self Gravity

ABSTRACT We investigate how a protoplanetary disc’s susceptibility to gravitational instabilities and fragmentation depends on the mass of its host star. We use 1D disc models in conjunction with 3D smoothed particle hydrodynamics simulations to determine the critical disc-to-star mass ratios at which discs become unstable against fragmentation, finding that discs become increasingly prone to the effects of self-gravity as we increase the host star mass. The actual limit for stability is sensitive to the disc temperature, so if the disc is optically thin stellar irradiation can dramatically stabilize discs against gravitational instability. However, even when this is the case we find that discs around 2 M⊙ stars are prone to fragmentation, which will act to produce wide-orbit giant planets and brown dwarfs. The consequences of this work are twofold: that low-mass stars could in principle support high disc-to-star mass ratios, and that higher mass stars have discs that are more prone to fragmentation, which is qualitatively consistent with observations that favour high-mass wide-orbit planets around higher mass stars. We also find that the initial masses of these planets depends on the temperature in the disc at large radii, which itself depends on the level of stellar irradiation.

scholarly journals Self-gravitating disks in binary systems: an SPH approach

2019 ◽  
Vol 628 ◽  
pp. A82
Author(s):  
L. D. Pinto ◽  
R. Capuzzo-Dolcetta ◽  
G. Magni
Keyword(s):  
Smoothed Particle Hydrodynamics ◽  
Binary Systems ◽  
Open Clusters ◽  
Star Mass ◽  
Particle Hydrodynamics ◽  
Smoothed Particle ◽  
Sph Algorithm ◽  
The Stability ◽  
Self Gravity

The study of the stability of massive gaseous disks around a star in a nonisolated context is a difficult task and becomes even more complicated for disks that are hosted by binary systems. The role of self-gravity is thought to be significant when the ratio of the disk-to-star mass is non-negligible. To solve these problems, we implemented, tested, and applied our own smoothed particle hydrodynamics (SPH) algorithm. The code (named GaSPH) passed various quality tests and shows good performances, and it can therefore be reliably applied to the study of disks around stars when self-gravity needs to be accounted for. We here introduce and describe the algorithm, including some performance and stability tests. This paper is the first part of a series of studies in which self-gravitating disks in binary systems are let evolve in larger environments such as open clusters.

scholarly journals The Circumstellar Environment of Embedded Massive Stars

2002 ◽  
Vol 12 ◽  
pp. 143-145 ◽  
Author(s):  
Lee G. Mundy ◽  
Friedrich Wyrowski ◽  
Sarah Watt
Keyword(s):  
Massive Star ◽  
Massive Stars ◽  
Low Mass Stars ◽  
Submillimeter Wavelength ◽  
Star Forming ◽  
Star Forming Regions ◽  
Low Mass ◽  
Circumstellar Environments ◽  
Near Future

Millimeter and submillimeter wavelength images of massive star-forming regions are uncovering the natal material distribution and revealing the complexities of their circumstellar environments on size scales from parsecs to 100’s of AU. Progress in these areas has been slower than for low-mass stars because massive stars are more distant, and because they are gregarious siblings with different evolutionary stages that can co-exist even within a core. Nevertheless, observational goals for the near future include the characterization of an early evolutionary sequence for massive stars, determination if the accretion process and formation sequence for massive stars is similar to that of low-mass stars, and understanding of the role of triggering events in massive star formation.

scholarly journals Ultra-deep tidal disruption events: prompt self-intersections and observables

2019 ◽  
Vol 488 (4) ◽  
pp. 5267-5278 ◽  
Author(s):  
Siva Darbha ◽  
Eric R Coughlin ◽  
Daniel Kasen ◽  
Chris Nixon
Keyword(s):  
Close Agreement ◽  
Tidal Disruption ◽  
X Ray ◽  
Analytic Estimate ◽  
Smoothed Particle ◽  
Solar Type ◽  
General Relativistic ◽  
Low Mass ◽  
Smoothed Particle Hydrodynamic ◽  
Schwarzschild Radius

ABSTRACT A star approaching a supermassive black hole (SMBH) can be torn apart in a tidal disruption event (TDE). We examine ultra-deep TDEs, a new regime in which the disrupted debris approaches close to the black hole’s Schwarzschild radius, and the leading part intersects the trailing part at the first pericentre passage. We calculate the range of penetration factors β versus SMBH masses M that produce these prompt self-intersections using a Newtonian analytic estimate and a general relativistic (GR) geodesic model. We find that significant self-intersection of Solar-type stars requires β ∼ 50–127 for M/M⊙ = 104, down to β ∼ 5.6–5.9 forM/M⊙ = 106. We run smoothed particle hydrodynamic (SPH) simulations to corroborate our calculations and find close agreement, with a slightly shallower dependence on M. We predict that the shock from the collision emits an X-ray flare lasting t ∼ 2 s with L ∼ 1047 erg s−1 at E ∼ 2 keV, and the debris has a prompt accretion episode lasting t ∼ several minutes. The events are rare and occur with a rate $\dot{N} \lesssim 10^{-7}$ Mpc−3 yr−1. Ultra-deep TDEs can probe the strong gravity and demographics of low-mass SMBHs.

scholarly journals Circumstellar Disks in Very Young Embedded Clusters

2013 ◽  
Vol 8 (S299) ◽  
pp. 165-166
Author(s):  
Naibí Mariñas ◽  
Elizabeth A. Lada ◽  
Paula S. Teixeira ◽  
Charles J. Lada
Keyword(s):  
Circumstellar Disks ◽  
Solar Mass ◽  
Low Mass Stars ◽  
Near Ir ◽  
Lower Disk ◽  
Low Mass ◽  
Embedded Clusters ◽  
Ir Photometry

AbstractWe used FLAMINGOS near-IR photometry and spectroscopy and Spitzer mid-IR photometry to study disk fractions in the 1 to 2 Myr old NGC2264 clusters. We find that stars with masses < 0.3 solar masses have lower disk fractions than stars of solar mass or higher at these early ages. We also find that most disks disappear within the first 4 Myr, which is consistent with previous studies of disk lifetimes. Our study suggests that either some very low mass stars form without disks or that their disks are less massive and/or colder than predicted from models and not detected with Spitzer/Flamingos sensitivities.

scholarly journals Episodic accretion in binary protostars emerging from self-gravitating solar mass cores

2018 ◽  
Vol 614 ◽  
pp. A53 ◽  
Author(s):  
R. Riaz ◽  
S. Vanaverbeke ◽  
D. R. G. Schleicher
Keyword(s):  
Molecular Cloud ◽  
Accretion Rate ◽  
Solar Mass ◽  
Multiple Systems ◽  
Average Mass ◽  
Triple Systems ◽  
Large Spread ◽  
Low Mass ◽  
Over Time

Observations show a large spread in the luminosities of young protostars, which are frequently explained in the context of episodic accretion. We tested this scenario with numerical simulations that follow the collapse of a solar mass molecular cloud using the GRADSPH code, thereby varying the strength of the initial perturbations and temperature of the cores. A specific emphasis of this paper is to investigate the role of binaries and multiple systems in the context of episodic accretion and to compare their evolution to the evolution in isolated fragments. Our models form a variety of low-mass protostellar objects including single, binary, and triple systems in which binaries are more active in exhibiting episodic accretion than isolated protostars. We also find a general decreasing trend in the average mass accretion rate over time, suggesting that the majority of the protostellar mass is accreted within the first 105 years. This result can potentially help to explain the surprisingly low average luminosities in the majority of the protostellar population.

scholarly journals The rotation of very low-mass stars and brown dwarfs

2007 ◽  
Vol 3 (S243) ◽  
pp. 241-248
Author(s):  
Jochen Eislöffel ◽  
Alexander Scholz
Keyword(s):  
Angular Momentum ◽  
Brown Dwarfs ◽  
Magnetic Interaction ◽  
Stellar Winds ◽  
Solar Mass ◽  
Low Mass Stars ◽  
Angular Momentum Loss ◽  
Rotational Evolution ◽  
Solar Type ◽  
Low Mass

AbstractThe evolution of angular momentum is a key to our understanding of star formation and stellar evolution. The rotational evolution of solar-mass stars is mostly controlled by magnetic interaction with the circumstellar disc and angular momentum loss through stellar winds. Major differences in the internal structure of very low-mass stars and brown dwarfs – they are believed to be fully convective throughout their lives, and thus should not operate a solar-type dynamo – may lead to major differences in the rotation and activity of these objects. Here, we report on observational studies to understand the rotational evolution of the very low-mass stars and brown dwarfs.

scholarly journals Dependence of star formation on initial conditions and molecular cloud structure

2010 ◽  
Vol 6 (S270) ◽  
pp. 133-140
Author(s):  
Matthew R. Bate
Keyword(s):  
Star Formation ◽  
Molecular Cloud ◽  
Initial Conditions ◽  
Small Scale ◽  
Low Mass Stars ◽  
Cloud Structure ◽  
Low Mass ◽  
Stellar Properties ◽  
Stellar Masses ◽  
Formation Of Groups

AbstractI review what has been learnt so far regarding the origin of stellar properties from numerical simulations of the formation of groups and clusters of stars. In agreement with observations, stellar properties are found to be relatively robust to variations of initial conditions in terms of molecular cloud structure and kinetics, as long as extreme initial conditions (e.g. strong central condensation, weak or no turbulence) and small-scale driving are avoided, but properties may differ between bound and unbound clouds. Radiative feedback appears crucial for setting stellar masses, even for low-mass stars, while magnetic fields can provide low star formation rates.

Sign in / Sign up

Export Citation Format

Share Document