scholarly journals Orbit circularization time in binary stellar systems

1984 ◽  
Vol 105 ◽  
pp. 411-414 ◽  
Author(s):  
M. Mayor ◽  
J.-C. Mermilliod
Keyword(s):  
Time Scale ◽  
Dynamical Evolution ◽  
Open Clusters ◽  
Spectroscopic Binaries ◽  
Stellar Systems ◽  
Orbital Parameters ◽  
Short Period ◽  
Red Giant

We have analyzed the orbital parameters of 33 red dwarf and 17 red giant spectroscopic binaries belonging to open clusters to deduce the time-scale for orbital circularization. The dynamical evolution of BD +23°635, a short period binary member of the Hyades, should result in the formation either of a cataclysmic binary or a WUMa system.

scholarly journals OCCASO – III. Iron peak and α elements of 18 open clusters. Comparison with chemical evolution models and field stars

2019 ◽  
Vol 490 (2) ◽  
pp. 1821-1842 ◽  
Author(s):  
L Casamiquela ◽  
S Blanco-Cuaresma ◽  
R Carrera ◽  
L Balaguer-Núñez ◽  
C Jordi ◽  
...  
Keyword(s):  
Chemical Evolution ◽  
Open Cluster ◽  
Dynamical Evolution ◽  
Open Clusters ◽  
Chemical Abundances ◽  
Homogeneous Sample ◽  
Giant Stars ◽  
Stellar Nucleosynthesis ◽  
Solar Abundances ◽  
Red Giant

ABSTRACT The study of open-cluster chemical abundances provides insights on stellar nucleosynthesis processes and on Galactic chemo-dynamical evolution. In this paper we present an extended abundance analysis of 10 species (Fe, Ni, Cr, V, Sc, Si, Ca, Ti, Mg, O) for red giant stars in 18 OCCASO clusters. This represents a homogeneous sample regarding the instrument features, method, line list and solar abundances from confirmed member stars. We perform an extensive comparison with previous results in the literature, and in particular with the Gaia FGK Benchmark stars Arcturus and $\mu$-Leo. We investigate the dependence of [X/Fe] with metallicity, Galactocentric radius (6.5 kpc < RGC < 11 kpc), age (0.3 Gyr < Age < 10 Gyr), and height above the plane (|z| < 1000 pc). We discuss the observational results in the chemo-dynamical framework, and the radial migration impact when comparing with chemical evolution models. We also use APOGEE DR14 data to investigate the differences between the abundance trends in RGC and |z| obtained for clusters and for field stars.

scholarly journals Statistical Properties of Solar-Type Close Binaries

2004 ◽  
Vol 191 ◽  
pp. 20-27
Author(s):  
J.-L. Halbwachs ◽  
M. Mayor ◽  
S. Udry ◽  
F. Arenou
Keyword(s):  
Binary Stars ◽  
Equal Mass ◽  
Open Clusters ◽  
Statistical Properties ◽  
Spectroscopic Binaries ◽  
Close Binary ◽  
Close Binaries ◽  
Multiple Systems ◽  
Short Period ◽  
Mass Ratios

AbstractTwo Coravel radial velocity surveys dedicated to F7-K field dwarfs and to open clusters are merged in order to investigate the statistical properties of binaries with periods up to 10 years. Thanks to the accurate trigonometric parallaxes provided by Hipparcos, an unbiased sample of spectroscopic binaries (SB) is selected. After correction for the uncertainties of the measurements, the following results are obtained: 1. The distribution of mass ratios exhibits a peak for equal-mass binaries (twins), which is higher for short-period binaries than for long-period binaries. 2. Apart from the twins, the distribution of mass ratios exhibits a broad peak from 0.2 to 0.6. 3. The orbital eccentricities of twins are slightly smaller than those of other binaries. 4. An excess of SB is observed with periods shorter than about 50 days in comparison with the Duquennoy and Mayor log-normal distribution of periods. These features suggest that close binary stars are generated by two different processes. A possible difference could come from the accretion onto the binary, for instance from a common envelope or from a circumbinary disk. Alternatively, twins could come from dynamic evolution of multiple systems. It is not clear whether the formation models are already sufficiently elaborated to reproduce our statistics.

scholarly journals Giant Planets, Tiny Stars: Producing Short-period Planets around White Dwarfs with the Eccentric Kozai–Lidov Mechanism

2021 ◽  
Vol 922 (1) ◽  
pp. 4
Author(s):  
Alexander P. Stephan ◽  
Smadar Naoz ◽  
B. Scott Gaudi
Keyword(s):  
Direct Evidence ◽  
Giant Planet ◽  
Giant Planets ◽  
Tidal Effects ◽  
Stellar Envelope ◽  
Orbital Parameters ◽  
Short Period ◽  
Migration Mechanism ◽  
Red Giant ◽  
Host Stars

Abstract The recent discoveries of WD J091405.30+191412.25 (WD J0914 hereafter), a white dwarf (WD) likely accreting material from an ice-giant planet, and WD 1856+534 b (WD 1856 b hereafter), a Jupiter-sized planet transiting a WD, are the first direct evidence of giant planets orbiting WDs. However, for both systems, the observations indicate that the planets’ current orbital distances would have put them inside the stellar envelope during the red-giant phase, implying that the planets must have migrated to their current orbits after their host stars became WDs. Furthermore, WD J0914 is a very hot WD with a short cooling time that indicates a fast migration mechanism. Here, we demonstrate that the Eccentric Kozai–Lidov Mechanism, combined with stellar evolution and tidal effects, can naturally produce the observed orbital configurations, assuming that the WDs have distant stellar companions. Indeed, WD 1856 is part of a stellar triple system, being a distant companion to a stellar binary. We provide constraints for the orbital and physical characteristics for the potential stellar companion of WD J0914 and determine the initial orbital parameters of the WD 1856 system.

scholarly journals Radial velocities with CORAVEL: results on stellar variability and duplicity

1986 ◽  
Vol 118 ◽  
pp. 385-400
Author(s):  
G. Burki ◽  
M. Mayor
Keyword(s):  
Dynamical Evolution ◽  
Distribution Functions ◽  
Open Clusters ◽  
Formation Mechanisms ◽  
Radial Velocity Curve ◽  
Stellar Radius ◽  
Orbital Parameters ◽  
Pulsating Stars ◽  
Rr Lyrae ◽  
The Galaxy

The complete radial velocity curve has been determined with CORAVEL for many pulsating stars of various classes: cepheid stars in the Galaxy and in the Magellanic Clouds, RR Lyrae, δ Scuti and SX Phoenicis stars. These measurements allow the determination of the radius variation and of the surface acceleration of these stars. In addition, the mean stellar radius of many of these stars has been determined by applying the Baade-Wesselink method.Systematic surveys of definite groups of binary or multiple stars are in progress with CORAVEL in order to determine the distribution functions of the orbital parameters. The eccentricity distributions for the binaries in the open clusters Pleiades, Praesepe, Coma Ber and Hyades are presented and their dependence on the physical processes (star formation mechanisms, mass exchange, tidal circularization, dynamical evolution) is briefly discussed.

scholarly journals Low–Mass He WDs and Millisecond Pulsars Age Determination

2000 ◽  
Vol 177 ◽  
pp. 631-632
Author(s):  
J. Antipova ◽  
Ene Ergma ◽  
M. J. Sarna
Keyword(s):  
Neutron Stars ◽  
Orbital Period ◽  
Time Scale ◽  
Age Determination ◽  
Close Binary ◽  
Orbital Parameters ◽  
History Of ◽  
Low Mass ◽  
Binary Evolution ◽  
Red Giant

It is accepted that the formation of a millisecond binary pulsar (MBP) with a low–mass companion may be explained as the end–point of close binary evolution in which an old pulsar is spun–up by accretion from the red giant (Bhattacharaya & van den Heuvel 1991). In this paper we shall discuss the cooling properties of the helium white dwarfs (WD) in short orbital period MBP systems PSR J0437–4715, PSR J0751+1807 and PSR J1012+5307, without referring to the rotational history of neutron stars (NS).Below we discuss observational data for several system for which the results of our calculations (Sarna, Antipova, & Muslimov 1998; Sarna, Ergma, & Antipova 1999) may be applied, by taking into account the orbital parameters of the system, the pulsar spin-down time, and the WD cooling time-scale.

scholarly journals The Dynamical Evolution of Young Open Clusters

1985 ◽  
Vol 113 ◽  
pp. 463-465
Author(s):  
Michael Margulis ◽  
Charles J. Lada ◽  
David Dearborn
Keyword(s):  
Potential Function ◽  
Molecular Clouds ◽  
Initial Conditions ◽  
Stellar System ◽  
Dynamical Evolution ◽  
Mass Function ◽  
Open Clusters ◽  
Stellar Systems ◽  
Spherically Symmetric ◽  
Star Forming

Using numerical N-body calculations we have simulated the dynamical evolution of young clusters as they emerge from molecular clouds. Starting with initially virialized systems of stars and gas we follow the evolution of these systems from the time immediately after the stars have formed in a cloud until a time long after all the residual star-forming gas has been dispersed. In the models stellar systems were composed of 50, and in some cases 100, stars and these stars were represented as point masses. The stellar mass function followed a power law with an index of −2.5 and ranged over two decades in mass (Scalo 1978). Gas in the models was represented as an extra term in the gravitational potential function governing stellar motions, and was set to follow a density distribution corresponding to a spherically symmetric Plummer potential function (Plummer 1911). Starting with these initial conditions, stellar motions were then integrated and evolution of each stellar system was followed as gas was dispersed from the vicinity of the stars as a function of time.

scholarly journals The multiplicity of massive stars

2010 ◽  
Vol 6 (S272) ◽  
pp. 474-485 ◽  
Author(s):  
Hugues Sana ◽  
Christopher J. Evans
Keyword(s):  
Break Point ◽  
Equal Mass ◽  
Current Data ◽  
Open Clusters ◽  
Spectroscopic Binaries ◽  
Spectroscopic Binary ◽  
Direct Measurements ◽  
Short Period ◽  
Homogeneous Fraction ◽  
Astrophysical Objects

AbstractBinaries are excellent astrophysical laboratories that provide us with direct measurements of fundamental stellar parameters. Compared to single isolated stars, multiplicity induces new processes, offering the opportunity to confront our understanding of a broad range of physics under the extreme conditions found in, and close to, astrophysical objects.In this contribution, we will discuss the parameter space occupied by massive binaries, and the observational means to investigate it. We will review the multiplicity fraction of OB stars within each regime, and in different astrophysical environments. In particular we will compare the O star spectroscopic binary fraction in nearby open clusters and we will show that the current data are adequately described by an homogeneous fraction of f ≈ 0.44.We will also summarize our current understanding of the observed parameter distributions of O + OB spectroscopic binaries. We will show that the period distribution is overabundant in short period binaries and that it can be described by a bi-modal Öpik law with a break point around P ≈ 10 d. The distribution of the mass-ratios shows no indication for a twin population of equal mass binaries and seems rather uniform in the range 0.2 ≤ q = M2/M1 ≤ 1.0.

scholarly journals Investigating surface correction relations for RGB stars

2020 ◽  
Vol 495 (4) ◽  
pp. 4965-4980 ◽  
Author(s):  
Andreas Christ Sølvsten Jørgensen ◽  
Josefina Montalbán ◽  
Andrea Miglio ◽  
Ben M Rendle ◽  
Guy R Davies ◽  
...  
Keyword(s):  
Surface Effect ◽  
Dynamical Evolution ◽  
Systematic Errors ◽  
Open Clusters ◽  
Eclipsing Binaries ◽  
Stellar Structure ◽  
Red Giants ◽  
Red Giant ◽  
Stellar Oscillation ◽  
Surface Correction

ABSTRACT State-of-the-art stellar structure and evolution codes fail to adequately describe turbulent convection. For stars with convective envelopes such as red giants, this leads to an incomplete depiction of the surface layers. As a result, the predicted stellar oscillation frequencies are haunted by systematic errors, the so-called surface effect. Different empirically and theoretically motivated correction relations have been proposed to deal with this issue. In this paper, we compare the performance of these surface correction relations for red giant branch stars. For this purpose, we apply the different surface correction relations in asteroseismic analyses of eclipsing binaries and open clusters. In accordance with previous studies of main-sequence stars, we find that the use of different surface correction relations biases the derived global stellar properties, including stellar age, mass, and distance estimates. We, furthermore, demonstrate that the different relations lead to the same systematic errors for two different open clusters. Our results overall discourage from the use of surface correction relations that rely on reference stars to calibrate free parameters. Due to the demonstrated systematic biasing of the results, the use of appropriate surface correction relations is imperative to any asteroseismic analysis of red giants. Accurate mass, age, and distance estimates for red giants are fundamental when addressing questions that deal with the chemo-dynamical evolution of the Milky Way galaxy. In this way, our results also have implications for fields such as galactic archaeology that draw on findings from stellar physics.

scholarly journals Anomalous Cepheids and Population II Blue Stragglers

1989 ◽  
Vol 111 ◽  
pp. 215-245
Author(s):  
James M. Nemec
Keyword(s):  
Globular Cluster ◽  
Time Scale ◽  
Binary Systems ◽  
Direct Evidence ◽  
Stellar Systems ◽  
Low Density ◽  
Instability Strip ◽  
Blue Stragglers ◽  
Short Period ◽  
Contact Binaries

AbstractRecent studies of anomalous Cepheids (ACs) and Pop II blue stragglers (BSs), including photometrically variable BSs (VBSs), are reviewed. The VBSs represent about 25% of the BSs, the majority of which are SX Phe short-period variables in the Cepheid instability strip. Mass estimates derived using various techniques suggest that both ACs and BSs are relatively massive (about 1.0–1.6 Me). The recent discovery that two BSs in the globular cluster NGC 5466 are contact binaries, and the earlier discovery that one of the BSs in ω Cen is an eclipsing binary, provide direct evidence that at least some BSs are binary systems. If all BSs are binaries, and the time scale for coalescence is a few Gyr, then the majority are likely to be coalesced. Because ACs and BSs are found in the same stellar systems, and are probably related through their evolution, it is highly likely that most ACs are also coalesced binary systems. The fact that ACs and BSs are found only in low density environments, suggests that they were primordial binaries.

scholarly journals Orbital Parameters and Binary Properties of 37 FGK Stars in the Cores of Open Clusters NGC 2516 and NGC 2422

2021 ◽  
Vol 162 (6) ◽  
pp. 285
Author(s):  
Isabel Lipartito ◽  
John I. Bailey III ◽  
Timothy D. Brandt ◽  
Benjamin A. Mazin ◽  
Mario Mateo ◽  
...  
Keyword(s):  
Open Cluster ◽  
Open Clusters ◽  
Spectroscopic Binaries ◽  
Proper Motions ◽  
Orbital Eccentricity ◽  
Critical Window ◽  
Cluster Membership ◽  
Orbital Parameters ◽  
Keplerian Orbits ◽  
Cluster Cores

Abstract We present orbits for 24 binaries in the field of open cluster NGC 2516 (∼150 Myr) and 13 binaries in the field of open cluster NGC 2422 (∼130 Myr) using results from a multiyear radial-velocity (RV) survey of the cluster cores. Six of these systems are double-lined spectroscopic binaries. We fit these RV variable systems with orvara, a MCMC-based fitting program that models Keplerian orbits. We use precise stellar parallaxes and proper motions from Gaia EDR3 to determine cluster membership. We impose a barycentric RV prior on all cluster members; this significantly improves our orbital constraints. Two of our systems have periods between five and 15 days, the critical window in which tides efficiently damp orbital eccentricity. These binaries should be included in future analyses of circularization across similarly-aged clusters. We also find a relatively flat distribution of binary mass ratios, consistent with previous work. With the inclusion of TESS light curves for all available targets, we identity target 378–036252 as a new eclipsing binary. We also identify a field star whose secondary has a mass in the brown dwarf range, as well as two cluster members whose RVs suggest the presence of an additional companion. Our orbital fits will help constrain the binary fraction and binary properties across stellar age and across stellar environment.

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