scholarly journals Planet Formation: An Optimized Population-synthesis Approach

2018 ◽  
Vol 865 (1) ◽  
pp. 30 ◽  
Author(s):  
John Chambers
Keyword(s):  
Planet Formation ◽  
Population Synthesis ◽  
Synthesis Approach

scholarly journals Metallicity effect and planet mass function in pebble-based planet formation models

2018 ◽  
Vol 619 ◽  
pp. A174 ◽  
Author(s):  
N. Brügger ◽  
Y. Alibert ◽  
S. Ataiee ◽  
W. Benz
Keyword(s):  
Internal Structure ◽  
Planet Formation ◽  
Large Fraction ◽  
Mass Function ◽  
Planetary Atmosphere ◽  
Population Synthesis ◽  
Core Accretion ◽  
Mass Functions ◽  
Synthesis Approach ◽  
Gaseous Envelope

Context. One of the main scenarios of planet formation is the core accretion model where a massive core forms first and then accretes a gaseous envelope. This core forms by accreting solids, either planetesimals or pebbles. A key constraint in this model is that the accretion of gas must proceed before the dissipation of the gas disc. Classical planetesimal accretion scenarios predict that the time needed to form a giant planet’s core is much longer than the time needed to dissipate the disc. This difficulty led to the development of another accretion scenario, in which cores grow by accretion of pebbles, which are much smaller and thus more easily accreted, leading to more rapid formation. Aims. The aim of this paper is to compare our updated pebble-based planet formation model with observations, in particular the well-studied metallicity effect. Methods. We adopt the Bitsch et al. (2015a, A&A, 575, A28) disc model and the Bitsch et al. (2015b, A&A, 582, A112) pebble model and use a population synthesis approach to compare the formed planets with observations. Results. We find that keeping the same parameters as in Bitsch et al. (2015b, A&A, 582, A112) leads to no planet growth due to a computation mistake in the pebble flux (2018b). Indeed a large fraction of the heavy elements should be put into pebbles (Zpeb∕Ztot = 0.9) in order to form massive planets using this approach. The resulting mass functions show a huge amount of giants and a lack of Neptune-mass planets, which are abundant according to observations. To overcome this issue we include the computation of the internal structure for the planetary atmosphere in our model. This leads to the formation of Neptune-mass planets but no observable giants. Furthermore, reducing the opacity of the planetary envelope more closely matches observations. Conclusions. We conclude that modelling the internal structure for the planetary atmosphere is necessary to reproduce observations.

scholarly journals Helium Star Donor Channel to Type Ia Supernovae and Their Surviving Companion Stars

2011 ◽  
Vol 7 (S281) ◽  
pp. 205-208
Author(s):  
Bo Wang ◽  
Zhanwen Han
Keyword(s):  
Main Sequence ◽  
Type Ia Supernovae ◽  
Population Synthesis ◽  
Short Delay ◽  
Delay Times ◽  
Spatial Velocity ◽  
Type Ia ◽  
Helium Star ◽  
Ia Supernovae ◽  
Synthesis Approach

AbstractEmploying Eggleton's stellar evolution code and assuming optically thick winds, we systematically studied the He star donor channel of Type Ia supernovae (SNe Ia), in which a carbon-oxygen white dwarf (WD) accretes material from a He main-sequence star or a He subgiant to increase its mass to the Chandrasekhar mass. We mapped out the initial parameters for producing SNe Ia in the orbital period–secondary mass plane for various WD masses from this channel. Based on a detailed binary population synthesis approach, we find that this channel can produce SNe Ia with short delay times (~100 Myr) implied by recent observations. We derived many properties of the surviving companions of this channel after SN explosion, which can be tested by future observations. We also find that the surviving companions from the SN explosion scenario have a high spatial velocity (>400 km/s), which could be an alternative origin for hypervelocity stars (HVSs), especially for HVSs such as US 708.

scholarly journals Magnetically induced termination of giant planet formation

2018 ◽  
Vol 619 ◽  
pp. A165 ◽  
Author(s):  
A. J. Cridland
Keyword(s):  
Magnetic Field ◽  
Cross Section ◽  
Planet Formation ◽  
Giant Planet ◽  
Effective Cross Section ◽  
Cold Start ◽  
Population Synthesis ◽  
Hot Start ◽  
Gas Accretion ◽  
Planetary Magnetic Field

Here a physical model for terminating giant planet formation is outlined and compared to other methods of late-stage giant planet formation. As has been pointed out before, gas accreting into a gap and onto the planet will encounter the planetary dynamo-generated magnetic field. The planetary magnetic field produces an effective cross section through which gas is accreted. Gas outside this cross section is recycled into the protoplanetary disk, hence only a fraction of mass that is accreted into the gap remains bound to the planet. This cross section inversely scales with the planetary mass, which naturally leads to stalled planetary growth late in the formation process. We show that this method naturally leads to Jupiter-mass planets and does not invoke any artificial truncation of gas accretion, as has been done in some previous population synthesis models. The mass accretion rate depends on the radius of the growing planet after the gap has opened, and we show that so-called hot-start planets tend to become more massive than cold-start planets. When this result is combined with population synthesis models, it might show observable signatures of cold-start versus hot-start planets in the exoplanet population.

WD+AGB star systems as the progenitors of type Ia supernovae

2018 ◽  
Vol 14 (S343) ◽  
pp. 540-541
Author(s):  
Bo Wang
Keyword(s):  
Type Ia Supernovae ◽  
Population Synthesis ◽  
Final Phase ◽  
Common Envelope ◽  
The Core ◽  
Delay Times ◽  
Careful Treatment ◽  
Type Ia ◽  
Ia Supernovae ◽  
Synthesis Approach

AbstractWD+AGB star systems have been suggested as an alternative way for producing type Ia supernovae (SNe Ia), known as the core-degenerate (CD) scenario. In the CD scenario, SNe Ia are produced at the final phase during the evolution of common-envelope through a merger between a carbon-oxygen (CO) WD and the CO core of an AGB secondary. However, the rates of SNe Ia from this scenario are still uncertain. In this work, I carried out a detailed investigation on the CD scenario based on a binary population synthesis approach. I found that the Galactic rates of SNe Ia from this scenario are not more than 20% of total SNe Ia due to more careful treatment of mass transfer, and that their delay times are in the range of ∼90 − 2500 Myr, mainly contributing to the observed SNe Ia with short and intermediate delay times.

scholarly journals A stellar population synthesis approach to the Oosterhoff dichotomy

2014 ◽  
Vol 444 (2) ◽  
pp. 1862-1872 ◽  
Author(s):  
A. Sollima ◽  
S. Cassisi ◽  
G. Fiorentino ◽  
R. G. Gratton
Keyword(s):  
Stellar Population ◽  
Population Synthesis ◽  
Stellar Population Synthesis ◽  
Synthesis Approach

scholarly journals New population synthesis approach: The golden path to constrain stellar and galactic physics

2019 ◽  
Vol 15 (S357) ◽  
pp. 184-187
Author(s):  
Nadège Lagarde ◽  
Céline Reylé
Keyword(s):  
White Dwarfs ◽  
European Space Agency ◽  
Chemical Properties ◽  
Population Synthesis ◽  
Chemical Abundances ◽  
Giant Stars ◽  
Red Giant ◽  
Stellar Masses ◽  
First Time ◽  
Synthesis Approach

AbstractThe cornerstone mission of the European Space Agency, Gaia, has revealed properties of 260 000 white dwarfs in the Galaxy, allowing us for the first time to constrain the evolution of white dwarfs with a large sample. Complementary surveys (CoRoT, Kepler, K2, APOGEE and Gaia-ESO), will revolutionize our understanding of the formation and history of our Galaxy, providing accurate stellar masses, radii, ages, distances, and chemical properties for very large samples of stars across different Galactic stellar populations. To exploit the potential of the combination of spectroscopic, seismic and astrometric observations, the population synthesis approach is a very crucial and efficient tool. We develop the Besançon Galaxy model (BGM, Lagarde et al.2017) for which stellar evolution predictions are included, providing the global asteroseismic properties and the surface chemical abundances along the evolution of low- and intermediate-mass stars. For the first time, the BGM can explore the effects of an extra-mixing occurring in red-giant stars Lagarde et al.2019, changing their stellar properties. The next step is to model a consistent treatment of giant stars and their remnants (e.g., white dwarfs). This kind of improvement would help us to constrain stellar and Galactic evolutions.

scholarly journals The evolution of stellar triples

2020 ◽  
Vol 640 ◽  
pp. A16 ◽  
Author(s):  
S. Toonen ◽  
S. Portegies Zwart ◽  
A. S. Hamers ◽  
D. Bandopadhyay
Keyword(s):  
Mass Transfer ◽  
Population Synthesis ◽  
Transfer Event ◽  
Term Evolution ◽  
Body Dynamics ◽  
Large Populations ◽  
Three Body ◽  
Synthesis Approach ◽  
Hubble Time

Context. Many stars do not live alone, but instead have one or more stellar companions. Observations show that these binaries, triples, and higher-order multiples are common. While the evolution of single stars and binaries have been studied extensively, the same is not true for the evolution of stellar triples. Aims. To fill in this gap in our general understanding of stellar lives, we aim to systematically explore the long-term evolution of triples and to map out the most common evolutionary pathways that triples go through. We quantitatively study how triples evolve, which processes are the most relevant, and how this differs from binary evoluion. Methods. We simulated the evolution of several large populations of triples with a population synthesis approach. We made use of the triple evolution code TRES to simulate the evolution of each triple in a consistent way, including three-body dynamics (based on the secular approach), stellar evolution, and their mutual influences. We simulated the evolution of the system up until mass transfer starts, the system becomes dynamically unstable, or a Hubble time has passed. Results. We find that stellar interactions are common in triples. Compared to a binary population, we find that the fraction of systems that can undergo mass transfer is ∼2−3 times larger in triples. Moreover, while orbits typically reach circularisation before Roche-lobe overflow in binaries, this is no longer true in triples. In our simulations, about 40% of systems retain an eccentric orbit. Additionally, we discuss various channels of triple evolution in detail, such as those where the secondary or the tertiary is the first star to initiate a mass transfer event.

scholarly journals The birthrates of SNe Ia in globular clusters

2015 ◽  
Vol 12 (S316) ◽  
pp. 343-344
Author(s):  
Bo Wang ◽  
Dongdong Liu
Keyword(s):  
Total Mass ◽  
Globular Clusters ◽  
Type Ia Supernovae ◽  
Population Synthesis ◽  
Type Ia ◽  
Ia Supernovae ◽  
Synthesis Approach ◽  
Degenerate Model

AbstractGlobular clusters has been proposed as testbeds for type Ia supernovae (SNe Ia). In this work, using a detailed binary population synthesis approach, we studied the birthrates of SNe Ia from various progenitor models in globular clusters, including the single-degenerate model, the double-degenerate model and the Sub-Chandrasekhar model. Here, a single starburst with a total mass of 106M⊙ is assumed.

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