scholarly journals Understanding the origin of white dwarf atmospheric pollution by dynamical simulations based on detected three-planet systems

2020 ◽  
Vol 499 (2) ◽  
pp. 1854-1869
Author(s):  
R F Maldonado ◽  
E Villaver ◽  
A J Mustill ◽  
M Chavez ◽  
E Bertone
Keyword(s):  
Atmospheric Pollution ◽  
Main Sequence ◽  
High Mass ◽  
Scattering Process ◽  
System Architectures ◽  
Tidal Forces ◽  
Dynamical Simulations ◽  
Low Mass ◽  
Dynamical Properties ◽  
Dynamical Instabilities

ABSTRACT Between 25 and 50 ${{\ \rm per\ cent}}$ of white dwarfs (WD) present atmospheric pollution by metals, mainly by rocky material, which has been detected as gas/dust discs, or in the form of photometric transits in some WDs. Planets might be responsible for scattering minor bodies that can reach stargazing orbits, where the tidal forces of the WD can disrupt them and enhance the chances of debris to fall on to the WD surface. The planet–planet scattering process can be triggered by the stellar mass-loss during the post main-sequence (MS) evolution of planetary systems. In this work, we continue the exploration of the dynamical instabilities that can lead to WD pollution. In a previous work, we explored two-planet systems found around MS stars and here we extend the study to three-planet system architectures. We evolved 135 detected three-planet systems orbiting MS stars to the WD phase by scaling their orbital architectures in a way that their dynamical properties are preserved using the N-body integrator package mercury. We find that 100 simulations (8.6 ${{\ \rm per\ cent}}$) are dynamically active (having planet losses, orbit crossing, and scattering) on the WD phase, where low-mass planets (1–100 M⊕) tend to have instabilities in Gyr time-scales, while high-mass planets (>100 M⊕) decrease the dynamical events more rapidly as the WD ages. Besides, 19 simulations (1.6 ${{\ \rm per\ cent}}$) were found to have planets crossing the Roche radius of the WD, where 9 of them had planet–star collisions. Our three-planet simulations have a slight increase in percentage of simulations that may contribute to the WD pollution than the previous study involving two-planet systems and have shown that planet–planet scattering is responsible of sending planets close to the WD, where they may collide directly to the WD, become tidally disrupted or circularize their orbits, hence producing pollution on the WD atmosphere.

scholarly journals Dynamical evolution of two-planet systems and its connection with white dwarf atmospheric pollution

2020 ◽  
Vol 497 (4) ◽  
pp. 4091-4106 ◽  
Author(s):  
R F Maldonado ◽  
E Villaver ◽  
A J Mustill ◽  
M Chavez ◽  
E Bertone
Keyword(s):  
Atmospheric Pollution ◽  
Ad Hoc ◽  
Planetary Systems ◽  
Dynamical Evolution ◽  
Asymptotic Giant Branch ◽  
Dynamical Instability ◽  
System Architectures ◽  
Tidal Forces ◽  
Eccentric Orbits ◽  
Current Paradigm

ABSTRACT Asteroid material is detected in white dwarfs (WDs) as atmospheric pollution by metals, in the form of gas/dust discs, or in photometric transits. Within the current paradigm, minor bodies need to be scattered, most likely by planets, into highly eccentric orbits where the material gets disrupted by tidal forces and then accreted on to the star. This can occur through a planet–planet scattering process triggered by the stellar mass-loss during the post main-sequence (MS) evolution of planetary systems. So far, studies of the N-body dynamics of this process have used artificial planetary system architectures built ad hoc. In this work, we attempt to go a step further and study the dynamical instability provided by more restrictive systems that, at the same time, allow us an exploration of a wider parameter space: the hundreds of multiple planetary systems found around MS stars. We find that most of our simulated systems remain stable during the MS, Red, and Asymptotic Giant Branch and for several Gyr into the WD phases of the host star. Overall, only ≈2.3 ${{\ \rm per\ cent}}$ of the simulated systems lose a planet on the WD as a result of dynamical instability. If the instabilities take place during the WD phase most of them result in planet ejections with just five planetary configurations ending as a collision of a planet with the WD. Finally 3.2 ${{\ \rm per\ cent}}$ of the simulated systems experience some form of orbital scattering or orbit crossing that could contribute to the pollution at a sustained rate if planetesimals are present in the same system.

scholarly journals A BINARY SCENARIO FOR THE FORMATION OF STRONGLY MAGNETIZED WHITE DWARFS

2011 ◽  
Vol 20 (supp02) ◽  
pp. 29-36 ◽  
Author(s):  
JASON NORDHAUS
Keyword(s):  
Magnetic Fields ◽  
High Field ◽  
White Dwarfs ◽  
Massive Star ◽  
Main Sequence ◽  
High Mass ◽  
Sequence Evolution ◽  
Main Sequence Stars ◽  
Low Mass ◽  
Initial Discovery

Since their initial discovery, the origin of isolated white dwarfs (WDs) with magnetic fields in excess of ~1 MG has remained a mystery. Recently, the formation of these high-field magnetic WDs has been observationally linked to strong binary interactions incurred during post-main-sequence evolution. Planetary, brown dwarf or stellar companions located within a few AU of main-sequence stars may become engulfed during the primary's expansion off the main sequence. Sufficiently low-mass companions in-spiral inside a common envelope until they are tidally shredded near the natal white dwarf. Formation of an accretion disk from the disrupted companion provides a source of turbulence and shear which act to amplify magnetic fields and transport them to the WD surface. We show that these disk-generated fields explain the observed range of magnetic field strengths for isolated, high-field magnetic WDs. Additionally, we discuss a high-mass binary analogue which generates a strongly-magnetized WD core inside a pre-collapse, massive star. Subsequent core-collapse to a neutron star may produce a magnetar.

scholarly journals Properties of barred galaxies in the MaNGA galaxy survey

2019 ◽  
Vol 14 (S353) ◽  
pp. 226-230
Author(s):  
Amelia Fraser-McKelvie ◽  
Michael Merrifield ◽  
Alfonso Aragón-Salamanca ◽  
Karen Masters ◽  
Keyword(s):  
Main Sequence ◽  
High Mass ◽  
Star Forming ◽  
Barred Galaxies ◽  
Wide Range ◽  
The Galaxy ◽  
Hα Emission ◽  
Low Mass ◽  
Formation And Evolution ◽  
Initial Results

AbstractWe present the initial results of a census of 684 barred galaxies in the MaNGA galaxy survey. This large sample contains galaxies with a wide range of physical properties, and we attempt to link bar properties to key observables for the whole galaxy. We find the length of the bar, when normalised for galaxy size, is correlated with the distance of the galaxy from the star formation main sequence, with more passive galaxies hosting larger-scale bars. Ionised gas is observed along the bars of low-mass galaxies only, and these galaxies are generally star-forming and host short bars. Higher-mass galaxies do not contain Hα emission along their bars, however, but are more likely to host rings or Hα at the centre and ends of the bar. Our results suggest that different physical processes are at play in the formation and evolution of bars in low- and high-mass galaxies.

scholarly journals Pre-main-sequence Stars in the SMC and LMC

1999 ◽  
Vol 190 ◽  
pp. 366-367 ◽  
Author(s):  
Wolfgang Brandner ◽  
Eva K. Grebel ◽  
Hans Zinnecker ◽  
Bernhard Brandl
Keyword(s):  
Stellar Population ◽  
Main Sequence ◽  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Magellanic Clouds ◽  
High Mass ◽  
Main Sequence Stars ◽  
Intermediate Mass ◽  
First Results ◽  
Low Mass

We present first results of a survey for pre-main-sequence stars in the Magellanic Clouds. Our search concentrated on NGC 346, the most prominent OB association in the Small Magellanic Cloud, and on the 30 Dor starburst cluster in the Large Magellanic Cloud. The identification of the young low- to intermediate-mass stellar population in the SMC and LMC allows us to study whether or not these populations formed simultaneously with high-mass stars, and to what an extent lower metallicity affects the low-mass IMF. We can also evaluate the duration of star formation in a starburst region.

Herbig Ae/Be stars with TGAS parallaxes in the HR diagram

2017 ◽  
Vol 12 (S330) ◽  
pp. 277-278
Author(s):  
Miguel Vioque ◽  
René D. Oudmaijer ◽  
Deborah Baines
Keyword(s):  
Main Sequence ◽  
Large Fraction ◽  
High Mass ◽  
Formation Mechanisms ◽  
Evolutionary Analysis ◽  
Be Stars ◽  
Intermediate Mass ◽  
Low Mass Stars ◽  
Low Mass ◽  
Hr Diagram

AbstractThe intermediate mass Herbig Ae/Be stars are young stars approaching the Main Sequence and are key to understanding the differences in formation mechanisms between magnetic low mass stars and non-magnetic high mass stars. A large fraction of known Herbig Ae/Be stars have TGAS parallaxes, which were used to derive luminosities and place 107 of these objects in the HR diagram, increasing the number of objects using directly determined parallaxes by a factor of 5. We also studied the characteristics of the infrared excesses of this set of Herbig Ae/Be stars and we linked our results to an evolutionary analysis.

The X-ray binary populations of M81 and M82

2018 ◽  
Vol 14 (S346) ◽  
pp. 344-349
Author(s):  
Paul H. Sell ◽  
Andreas Zezas ◽  
Stephen J. Williams ◽  
Jeff J. Andrews ◽  
Kosmas Gazeas ◽  
...  
Keyword(s):  
Mass Transfer ◽  
Globular Clusters ◽  
Luminosity Function ◽  
Main Sequence ◽  
The Other ◽  
High Mass ◽  
Early Type ◽  
X Ray ◽  
Star Forming ◽  
Low Mass

AbstractWe use deep Chandra and HST data to uniquely classify the X-ray binary (XRB) populations in M81 on the basis of their donor stars and local stellar populations (into early-type main sequence, yellow giant, supergiant, low-mass, and globular cluster). First, we find that more massive, redder, and denser globular clusters are more likely to be associated with XRBs. Second, we find that the high-mass XRBs (HMXBs) overall have a steeper X-ray luminosity function (XLF) than the canonical star-forming galaxy XLF, though there is some evidence of variations in the slopes of the sub-populations. On the other hand, the XLF of the prototypical starburst M82 is described by the canonical powerlaw (αcum ∼ 0.6) down to LX ∼ 1036 erg s−1. We attribute variations in XLF slopes to different mass transfer modes (Roche-lobe overflow versus wind-fed systems).

scholarly journals Evolution of Globular Clusters Including a Degenerate Component

1988 ◽  
Vol 126 ◽  
pp. 665-666
Author(s):  
Hyung Mok Lee
Keyword(s):  
Globular Clusters ◽  
Main Sequence ◽  
High Mass ◽  
Main Sequence Stars ◽  
Compact Binaries ◽  
The Core ◽  
Degenerate Component ◽  
Low Mass ◽  
Mass Segregation ◽  
Very High

Low mass X-ray sources observed in many globular clusters are usually interpreted as compact binaries with degenerate components (e.g., Hertz and Grindlay 1983). Degenerate stars can exist in globular clusters if the IMF contains a sufficiently large number of high mass stars. Since the main-sequence lifetime is a very steep function of stellar mass, most of degenerate stars can be regarded as primordial. If the typical mass of degenerate stars is higher than that of main-sequence stars, mass segregation makes the core crowded with degenerate stars. Tidally captured binaries between degenerates and main-sequence stars can abundantly form as the core density becomes very high.

scholarly journals Formation of compact systems of super-Earths via dynamical instabilities and giant impacts

2019 ◽  
Vol 491 (4) ◽  
pp. 5595-5620 ◽  
Author(s):  
Sanson T S Poon ◽  
Richard P Nelson ◽  
Seth A Jacobson ◽  
Alessandro Morbidelli
Keyword(s):  
Initial Conditions ◽  
Post Processing ◽  
Significant Modification ◽  
Kepler Mission ◽  
Giant Impacts ◽  
Low Mass ◽  
In Situ Formation ◽  
Dynamical Instabilities ◽  
Gaseous Envelopes

ABSTRACT The NASA’s Kepler mission discovered ∼700 planets in multiplanet systems containing three or more transiting bodies, many of which are super-Earths and mini-Neptunes in compact configurations. Using N-body simulations, we examine the in situ, final stage assembly of multiplanet systems via the collisional accretion of protoplanets. Our initial conditions are constructed using a subset of the Kepler five-planet systems as templates. Two different prescriptions for treating planetary collisions are adopted. The simulations address numerous questions: Do the results depend on the accretion prescription?; do the resulting systems resemble the Kepler systems, and do they reproduce the observed distribution of planetary multiplicities when synthetically observed?; do collisions lead to significant modification of protoplanet compositions, or to stripping of gaseous envelopes?; do the eccentricity distributions agree with those inferred for the Kepler planets? We find that the accretion prescription is unimportant in determining the outcomes. The final planetary systems look broadly similar to the Kepler templates adopted, but the observed distributions of planetary multiplicities or eccentricities are not reproduced, because scattering does not excite the systems sufficiently. In addition, we find that ∼1 per cent of our final systems contain a co-orbital planet pair in horseshoe or tadpole orbits. Post-processing the collision outcomes suggests that they would not significantly change the ice fractions of initially ice-rich protoplanets, but significant stripping of gaseous envelopes appears likely. Hence, it may be difficult to reconcile the observation that many low-mass Kepler planets have H/He envelopes with an in situ formation scenario that involves giant impacts after dispersal of the gas disc.

scholarly journals The nature of giant clumps in high-z discs: a deep-learning comparison of simulations and observations

2020 ◽  
Vol 501 (1) ◽  
pp. 730-746
Author(s):  
Omri Ginzburg ◽  
Marc Huertas-Company ◽  
Avishai Dekel ◽  
Nir Mandelker ◽  
Gregory Snyder ◽  
...  
Keyword(s):  
Neural Network ◽  
Deep Learning ◽  
Main Sequence ◽  
High Redshift ◽  
High Mass ◽  
Galactic Centre ◽  
Preferential Formation ◽  
Maximum Resolution ◽  
Supernova Feedback ◽  
Disc Galaxies

ABSTRACT We use deep learning to explore the nature of observed giant clumps in high-redshift disc galaxies, based on their identification and classification in cosmological simulations. Simulated clumps are detected using the 3D gas and stellar densities in the VELA zoom-in cosmological simulation suite, with ${\sim}25\ \rm {pc}$ maximum resolution, targeting main-sequence galaxies at 1 < z < 3. The clumps are classified as long-lived clumps (LLCs) or short-lived clumps (SLCs) based on their longevity in the simulations. We then train neural networks to detect and classify the simulated clumps in mock, multicolour, dusty, and noisy HST-like images. The clumps are detected using an encoder–decoder convolutional neural network (CNN), and are classified according to their longevity using a vanilla CNN. Tests using the simulations show our detector and classifier to be ${\sim}80{{\ \rm per\ cent}}$ complete and ${\sim}80{{\ \rm per\ cent}}$ pure for clumps more massive than ∼107.5 M⊙. When applied to observed galaxies in the CANDELS/GOODS S+N fields, we find both types of clumps to appear in similar abundances in the simulations and the observations. LLCs are, on average, more massive than SLCs by ∼0.5 dex, and they dominate the clump population above Mc ≳ 107.6 M⊙. LLCs tend to be found closer to the galactic centre, indicating clump migration to the centre or preferential formation at smaller radii. The LLCs are found to reside in high-mass galaxies, indicating better clump survivability under supernova feedback there, due to clumps being more massive in these galaxies. We find the clump masses and radial positions in the simulations and the observations to agree within a factor of 2.

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 $\sigma _{\log _{10}({M/M}_\odot)}\sim 0.47$).

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