scholarly journals Eccentricity distribution of wide low-mass binaries

2020 ◽  
Vol 496 (1) ◽  
pp. 987-993 ◽  
Author(s):  
Andrei Tokovinin
Keyword(s):  
Stellar Dynamics ◽  
Statistical Information ◽  
Solar Neighbourhood ◽  
Wide Binary ◽  
Eccentric Orbits ◽  
Wide Pairs ◽  
Low Mass ◽  
Orbital Periods ◽  
Relative Motions

ABSTRACT Distribution of eccentricities of very wide (up to 10 kau) low-mass binaries in the solar neighbourhood is studied using the catalogue of El-Badry and Rix (2018) based on Gaia. Direction and speed of relative motions in wide pairs contain statistical information on the eccentricity distribution, otherwise inaccessible owing to very long orbital periods. It is found that the eccentricity distribution is close to the linear (thermal) one f(e) = 2e. However, pairs with projected separations <200 au have less eccentric orbits, while f(e) for wide pairs with s > 1 kau appears to be slightly superthermal, with an excess of very eccentric orbits. Eccentricity of any wide binary can be constrained statistically using direction and speed of its motion. The thermal eccentricity distribution signals an important role of the stellar dynamics in the formation of wide binaries, although disc-assisted capture also can produce such pairs with eccentric orbits.

scholarly journals The White Dwarf Binary Pathways Survey −III. Contamination from hierarchical triples containing a white dwarf

2020 ◽  
Vol 494 (1) ◽  
pp. 915-922 ◽  
Author(s):  
F Lagos ◽  
M R Schreiber ◽  
S G Parsons ◽  
A Zurlo ◽  
D Mesa ◽  
...  
Keyword(s):  
White Dwarf ◽  
Binary Stars ◽  
Main Sequence Stars ◽  
Triple Systems ◽  
Compact Binary ◽  
Tidal Forces ◽  
Eccentric Orbits ◽  
Low Mass ◽  
Orbital Periods ◽  
Binary Evolution

ABSTRACT The White Dwarf Binary Pathways Survey aims at increasing the number of known detached A, F, G, and K main-sequence stars in close orbits with white dwarf companions (WD+AFGK binaries) to refine our understanding about compact binary evolution and the nature of Supernova Ia progenitors. These close WD+AFGK binary stars are expected to form through common envelope evolution, in which tidal forces tend to circularize the orbit. However, some of the identified WD+AFGK binary candidates show eccentric orbits, indicating that these systems are either formed through a different mechanism or perhaps they are not close WD+AFGK binaries. We observed one of these eccentric WD+AFGK binaries with SPHERE and find that the system TYC 7218-934-1 is in fact a triple system where the WD is a distant companion. The inner binary likely consists of the G-type star plus an unseen low-mass companion in an eccentric orbit. Based on this finding, we estimate the fraction of triple systems that could contaminate the WD+AFGK sample. We find that less than 15 per cent of our targets with orbital periods shorter than 100 d might be hierarchical triples.

scholarly journals The Role of Saturn's Oblateness in the Mimas-Tethys Resonance

1974 ◽  
Vol 62 ◽  
pp. 71-76
Author(s):  
R. Greenberg
Keyword(s):  
Saturn’S Satellites ◽  
Orbital Periods

Saturn's satellites Mimas and Tethys appear to be involved in a unique resonance. All orbit-orbit resonances, by definition, have the satellites' conjunction librating about some specific longitude. Equivalently, their orbital periods, measured relative to that longitude, are commensurable. Most orbit-orbit resonances are of the eccentricity-type; the conjunctions librate about the longitude of an apse of one orbit. The Mimas-Tethys resonance is of the inclination type.

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 TiNy TITANS: THE ROLE OF DWARF–DWARF INTERACTIONS IN LOW-MASS GALAXY EVOLUTION

2015 ◽  
Vol 805 (1) ◽  
pp. 2 ◽  
Author(s):  
S. Stierwalt ◽  
G. Besla ◽  
D. Patton ◽  
K. Johnson ◽  
N. Kallivayalil ◽  
...  
Keyword(s):  
Galaxy Evolution ◽  
Low Mass

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.

Circle-Drawing Movements at Different Speeds: Role of Inertial Anisotropy

2002 ◽  
Vol 88 (5) ◽  
pp. 2399-2407 ◽  
Author(s):  
Kerstin D. Pfann ◽  
Daniel M. Corcos ◽  
Charity G. Moore ◽  
Ziaul Hasan
Keyword(s):  
Individual Differences ◽  
Horizontal Plane ◽  
Upper Arm ◽  
Speed Dependence ◽  
Oval Shape ◽  
Circle Drawing ◽  
Relative Motions

This study investigated the role of inertial anisotropy at the hand in causing distortions in movement. Subjects drew circles in the horizontal plane at four locations in the workspace at three instructed paces using elbow and shoulder movements. Specifically, we tested two hypotheses, which we would expect if the anisotropy of inertia were not completely accounted for by the CNS when generating circle-drawing movements: 1) speed will affect the circularity of figures, with faster movements associated with greater elongation into an oval shape, irrespective of workspace location for configurations with a similar angle between the forearm and upper arm. 2) The elongation of the circle at fast speeds will be in the direction of least inertia. The results showed that despite individual differences in the speed dependence of the relative motions at the elbow and the shoulder, the circularity decreased (distortion increased) with increased speed, and workspace location had no effect on circularity. We also found that the elongation of the circles at fast speeds was in a direction close to but significantly different from the direction of least inertia for three workspace locations and was in the direction of least inertia for the fourth location. We suggest that the elongation results from lack of full accounting by the CNS of the anisotropy of viscosity and inertia.

scholarly journals A kinematically hot population of young stars in the solar neighbourhood

2020 ◽  
Vol 494 (2) ◽  
pp. 2429-2439 ◽  
Author(s):  
A S Binks ◽  
R D Jeffries ◽  
N J Wright
Keyword(s):  
Young Stars ◽  
Solar Neighbourhood ◽  
Mass Distributions ◽  
Systematic Effort ◽  
Low Mass ◽  
Moving Groups

ABSTRACT In the last three decades several hundred nearby members of young stellar moving groups (MGs) have been identified, but there has been less systematic effort to quantify or characterize young stars that do not belong to previously identified MGs. Using a kinematically unbiased sample of 225 lithium-rich stars within 100 pc, we find that only 50 ± 10 per cent of young (≲125 Myr), low-mass (0.5 < M/M⊙ < 1.0) stars, are kinematically associated with known MGs. Whilst we find some evidence that five of the non-MG stars may be connected with the Lower Centaurus–Crux association, the rest form a kinematically ‘hotter’ population, much more broadly dispersed in velocity, and with no obvious concentrations in space. The mass distributions of the MG members and non-MG stars are similar, but the non-MG stars may be older on average. We briefly discuss several explanations for the origin of the non-MG population.

scholarly journals The diverse origin of exoplanets' eccentricities & inclinations

2010 ◽  
Vol 6 (S276) ◽  
pp. 221-224
Author(s):  
Eric B. Ford
Keyword(s):  
Rotation Axis ◽  
Orbital Evolution ◽  
Giant Planets ◽  
Direct Imaging ◽  
Wide Binary ◽  
Hot Jupiters ◽  
Short Period ◽  
New Type ◽  
Low Mass ◽  
Diverse Origin

AbstractRadial velocity surveys have discovered over 400 exoplanets. While measuring eccentricities of low-mass planets remains a challenge, giant exoplanets display a broad range of orbital eccentricities. Recently, spectroscopic measurements during transit have demonstrated that the short-period giant planets (“hot-Jupiters”) also display a broad range of orbital inclinations (relative to the rotation axis of the host star). Both properties pose a challenge for simple disk migration models and suggest that late-stage orbital evolution can play an important role in determining the final architecture of planetary systems. One possible formation mechanism for the inclined hot-Jupiters is some form of eccentricity excitation (e.g., planet scattering, secular perturbations due to a distant planet or wide binary) followed tidal circularization. The planet scattering hypothesis also makes predictions for the population of planets at large separations. Recent discoveries of planets on wide orbits via direct imaging and highly anticipated results from upcoming direct imaging campaigns are poised to provide a new type of constraint on planet formation. This proceedings describes recent progress in understanding the formation of giant exoplanets.

scholarly journals Footprints of triggering in large area surveys of the nearby ISM and YSOs

2006 ◽  
Vol 2 (S237) ◽  
pp. 124-127
Author(s):  
L. Viktor Tóth ◽  
Zoltán T. Kiss
Keyword(s):  
Star Formation ◽  
Stellar Evolution ◽  
Large Area ◽  
Large Sample ◽  
Low Mass ◽  
Cold Core

AbstractOur goal is to evaluate the role of triggering effects on the star formation and early stellar evolution by presenting a statistically large sample of cloud and low-mass YSO data. We conducted large area surveys (ranging from 400 square-degree to 10800 square-degree) in optical, NIR and FIR. The distribution of the ISM and low-mass YSOs were surveyed. A relative excess was found statistically in the number of dense and cold core bearing clouds and low mass YSOs in the direction of the FIR loop shells indicating a possible excess in their formation.

scholarly journals Simulations of the IMF in Clusters

2010 ◽  
Vol 6 (S270) ◽  
pp. 151-158
Author(s):  
Ralph E. Pudritz
Keyword(s):  
Equations Of State ◽  
Stellar Dynamics ◽  
Mass Function ◽  
Initial Mass Function ◽  
Core Mass ◽  
Numerical Work ◽  
Computational Approaches ◽  
The Core ◽  
The Imf

AbstractWe review computational approaches to understanding the origin of the Initial Mass Function (IMF) during the formation of star clusters. We examine the role of turbulence, gravity and accretion, equations of state, and magnetic fields in producing the distribution of core masses - the Core Mass Function (CMF). Observations show that the CMF is similar in form to the IMF. We focus on feedback processes such as stellar dynamics, radiation, and outflows can reduce the accreted mass to give rise to the IMF. Numerical work suggests that filamentary accretion may play a key role in the origin of the IMF.

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