scholarly journals Mass transfer of low-mass binaries and chemical anomalies among unevolved stars in globular clusters

2020 ◽  
Vol 493 (4) ◽  
pp. 5479-5488
Author(s):  
Dandan Wei ◽  
Bo Wang ◽  
Xuefei Chen ◽  
Hailiang Chen ◽  
Lifang Li ◽  
...  
Keyword(s):  
Mass Transfer ◽  
Globular Clusters ◽  
Binary Systems ◽  
Evolutionary Models ◽  
Population Synthesis ◽  
Abundance Patterns ◽  
Angular Momentum Loss ◽  
Low Mass ◽  
Abundance Anomalies ◽  
Chemical Anomalies

ABSTRACT While it is well known that mass transfer in binaries can pollute the surfaces of the accretors, it is still unclear whether this mechanism can reproduce the observed chemical inhomogeneities in globular clusters. We study the surface abundances of the accretors in low-mass binaries, as a first step towards understanding whether mass transfer in low-mass binaries is one of the potential origins of the aforementioned abundance anomalies in globular clusters. We use the mesa (Modules for Experiments in Stellar Astrophysics) code to calculate binary evolutionary models with different initial donor masses between 0.9 and 1.9 $\rm {M}_\odot$ for an initial metallicity of Z = 0.0034. The results show that in some low-mass binary systems, the accretors exhibit peculiar chemical patterns when they are still unevolved stars, e.g. C and O depletion; Na and N enhancement; and constant Mg, Al, and C+N+O. The abundance patterns of the accretors are significantly different from their initial abundances (or that of normal single stars), and can match the observed populations. These abundance patterns strongly depend not only on the initial parameters of binaries (donor mass, mass ratio, and orbital period), but also on the assumptions regarding mass-transfer efficiency and angular momentum loss. These results support the hypothesis that mass transfer in low-mass binaries is, at least, partly responsible for the unevolved anomalous stars in globular clusters. More work on binary evolutionary models and binary population synthesis is required to fully evaluate the contribution of this scenario.

Constraining Progenitors of Observed Low-mass X-ray Binaries Using Convection and Rotation-Boosted Magnetic Braking

2021 ◽  
Vol 922 (2) ◽  
pp. 174
Author(s):  
Kenny X. Van ◽  
Natalia Ivanova
Keyword(s):  
Mass Transfer ◽  
Binary Systems ◽  
Formation Rate ◽  
Mass Transfer Rate ◽  
Population Synthesis ◽  
X Ray ◽  
Synthesis Technique ◽  
Low Mass ◽  
Magnetic Braking ◽  
X Ray Binaries

Abstract We present a new method for constraining the mass transfer evolution of low-mass X-ray binaries (LMXBs)—a reverse population synthesis technique. This is done using the detailed 1D stellar evolution code MESA (Modules for Experiments in Stellar Astrophysics) to evolve a high-resolution grid of binary systems spanning a comprehensive range of initial donor masses and orbital periods. We use the recently developed convection and rotation-boosted (CARB) magnetic braking scheme. The CARB magnetic braking scheme is the only magnetic braking prescription capable of reproducing an entire sample of well-studied persistent LMXBs—those with mass ratios, periods, and mass transfer rates that have been observationally determined. Using the reverse population synthesis technique, where we follow any simulated system that successfully reproduces an observed LMXB backward, we have constrained possible progenitors for each observed well-studied persistent LMXB. We also determined that the minimum number of LMXB formations in the Milky Way is 1500 per Gyr if we exclude Cyg X-2. For Cyg X-2, the most likely formation rate is 9000 LMXB Gyr−1. The technique we describe can be applied to any observed LMXB with well-constrained mass ratio, period, and mass transfer rate. With the upcoming GAIA DR3 containing information on binary systems, this technique can be applied to the data release to search for progenitors of observed persistent LMXBs.

scholarly journals Influence of the initial orbital period and accretion efficiency on the low-mass binary evolution

2021 ◽  
pp. 25-30
Author(s):  
J. Petrovic
Keyword(s):  
Mass Transfer ◽  
Orbital Period ◽  
White Dwarf ◽  
Binary Systems ◽  
Evolutionary Models ◽  
Stable Case ◽  
Long Period ◽  
Low Mass ◽  
Orbital Periods ◽  
Binary Evolution

This paper presents detailed evolutionary models of low-mass binary systems (1.25 + 1 M?) with initial orbital periods of 10, 50 and 100 days and accretion efficiency of 10%, 20%, 50%, and a conservative assumption. All models are calculated with the MESA (Modules for Experiments in Stellar Astrophysics) evolutionary code. We show that such binary systems can evolve via a stable Case B mass transfer into long period helium white dwarf systems.

scholarly journals The Chemical Inhomogeneity within Globular Clusters

1988 ◽  
Vol 126 ◽  
pp. 93-106
Author(s):  
John Norris
Keyword(s):  
Globular Cluster ◽  
Globular Clusters ◽  
Binary Systems ◽  
Chemical Inhomogeneity ◽  
Low Mass Stars ◽  
Stellar Collisions ◽  
Low Mass ◽  
Abundance Anomalies ◽  
Insight Into ◽  
The Way

Twenty years ago it was believed by most astronomers that globular clusters were chemically homogeneous - where by homogeneous one means that the outer layers of all stars within a given cluster are the same to within a few tens of percent. Today it is possible to defend the case that no Galactic globular cluster has this characteristic. The reason that this phenomenon has exercised the minds of so many groups in the past 15 years is exciting and obvious: if one can ascertain which are the relevant physical processes in operation, one stands to gain significant insight into both the way in which globular clusters formed and/or the way in which individual low mass stars evolve and mix the products of their nucleosynthesis into their outer layers. A second important driver at the back of the minds of workers in this field is the possible ramifications of an understanding of the phenomenon; for example, if one concludes that the abundance anomalies are being driven today by some particular effect (angular momentum, magnetic fields, interactions within binary systems, stellar collisions - or whatever) this may lead to insight into other important globular cluster phenomena (eg bimodal horizontal branches, gaps at the base of the giant branch, horizontal branch rotation, etc.)

scholarly journals Gone with the wind: the impact of wind mass transfer on the orbital evolution of AGB binary systems

2018 ◽  
Vol 618 ◽  
pp. A50 ◽  
Author(s):  
M. I. Saladino ◽  
O. R. Pols ◽  
E. van der Helm ◽  
I. Pelupessy ◽  
S. Portegies Zwart
Keyword(s):  
Mass Transfer ◽  
Angular Momentum ◽  
Stellar Wind ◽  
Binary Systems ◽  
Orbital Evolution ◽  
Momentum Loss ◽  
Angular Momentum Loss ◽  
Wind Velocities ◽  
Low Mass ◽  
Orbital Periods

In low-mass binary systems, mass transfer is likely to occur via a slow and dense stellar wind when one of the stars is in the asymptotic giant branch (AGB) phase. Observations show that many binaries that have undergone AGB mass transfer have orbital periods of 1–10 yr, at odds with the predictions of binary population synthesis models. In this paper we investigate the mass-accretion efficiency and angular-momentum loss via wind mass transfer in AGB binary systems and we use these quantities to predict the evolution of the orbit. To do so, we perform 3D hydrodynamical simulations of the stellar wind lost by an AGB star in the time-dependent gravitational potential of a binary system, using the AMUSE framework. We approximate the thermal evolution of the gas by imposing a simple effective cooling balance and we vary the orbital separation and the velocity of the stellar wind. We find that for wind velocities higher than the relative orbital velocity of the system the flow is described by the Bondi-Hoyle-Lyttleton approximation and the angular-momentum loss is modest, which leads to an expansion of the orbit. On the other hand, for low wind velocities an accretion disk is formed around the companion and the accretion efficiency as well as the angular-momentum loss are enhanced, implying that the orbit will shrink. We find that the transfer of angular momentum from the binary orbit to the outflowing gas occurs within a few orbital separations from the centre of mass of the binary. Our results suggest that the orbital evolution of AGB binaries can be predicted as a function of the ratio of the terminal wind velocity to the relative orbital velocity of the system, v∞/vorb. Our results can provide insight into the puzzling orbital periods of post-AGB binaries. The results also suggest that the number of stars entering into the common-envelope phase will increase, which can have significant implications for the expected formation rates of the end products of low-mass binary evolution, such as cataclysmic binaries, type Ia supernovae, and double white-dwarf mergers.

scholarly journals Contamination of RR Lyrae stars from Binary Evolution Pulsators

2015 ◽  
Vol 5 (1) ◽  
pp. 24-28
Author(s):  
P. Karczmarek
Keyword(s):  
Mass Transfer ◽  
Binary System ◽  
Synthesis Method ◽  
Population Synthesis ◽  
Rr Lyrae Stars ◽  
Rr Lyrae ◽  
Low Mass ◽  
Binary Evolution ◽  
Lyrae Stars ◽  
Range Of Values

A Binary Evolution Pulsator (BEP) is a low-mass (0.26 𝔐☉) member of a binary system, which pulsates as a result of a former mass transfer to its companion. The BEP mimics RR Lyrae-type pulsations, but has completely different internal structure and evolution history. Although there is only one known BEP (OGLE-BLG-RRLYR-02792), it has been estimated that approximately 0.2% of objects classified as RR Lyrae stars can be undetected Binary Evolution Pulsators. In the present work, this contamination value is re-evaluated using the population synthesis method. The output falls inside a range of values dependent on tuning the parameters in the StarTrack code, and varies from 0.06% to 0.43%.

scholarly journals The relation between recycled radio pulsars and wide low-mass X-ray binaries

1996 ◽  
Vol 160 ◽  
pp. 533-534
Author(s):  
Xiangdong Li ◽  
Zhenru Wang
Keyword(s):  
Mass Transfer ◽  
Neutron Star ◽  
Binary Systems ◽  
Accretion Rate ◽  
Rest Mass ◽  
Mass Transfer Rate ◽  
Radio Pulsars ◽  
Origin And Evolution ◽  
Low Mass ◽  
Field Decay

The origin and evolution of neutron star magnetic fields has been hotly debated for a long time. Spontaneous field decay was originally proposed with timescales of (5–10) × 106years, while another possible model which associates field decay with mass accretion in the evolution of binary systems has been suggested (see Bhattacharya & van den Heuvel 1991 for a review). The aim of this paper is to examine whether accretion-induced field decay can reproduce the observed properties of the wide binary radio pulsars in quantitative calculations.In a binary system consisting of a neutron star and a low-mass giant companion, if the initial orbital period is longer than 1 day, mass transfer, taking the form of Roche-lobe overflow, is driven by the nuclear evolution of the giant through radius expansion (Webbink et al. 1983). We assume the mass accretion rateṀof the neutron star is limited to the Eddington accretion rateṀE≃ 10−8M⊙yr−1. If the mass transfer rate is in excess ofṀE, the rest mass is blown from the system in the forms of jets or beams.

scholarly journals A nitrogen-enhanced metal-poor star discovered in the globular cluster ESO280−SC06

2019 ◽  
Vol 490 (1) ◽  
pp. 741-751 ◽  
Author(s):  
Jeffrey D Simpson ◽  
Sarah L Martell
Keyword(s):  
Globular Cluster ◽  
Globular Clusters ◽  
Binary Systems ◽  
Asymptotic Giant Branch ◽  
Red Giants ◽  
Horizontal Branch ◽  
Term Survival ◽  
Abundance Patterns ◽  
Metal Poor Star

ABSTRACT We report the discovery of the only very nitrogen-enhanced metal-poor star known in a Galactic globular cluster. This star, in the very metal-poor cluster ESO280−SC06 , has $[\textrm{N}/\textrm{Fe}]\, \gt +2.5$, while the other stars in the cluster show no obvious enhancement in nitrogen. Around 80 NEMP stars are known in the field, and their abundance patterns are believed to reflect mass transfer from a binary companion in the asymptotic giant branch phase. The dense environment of globular clusters is detrimental to the long term survival of binary systems, resulting in a low observed binary fraction among red giants and the near absence of NEMP stars. We also identify the first known horizontal branch members of ESO280−SC06 , which allow for a much better constraint on its distance. We calculate an updated orbit for the cluster based on our revised distance of 20.6 ± 0.5 kpc, and find no significant change to its orbital properties.

scholarly journals The EBLM project

2019 ◽  
Vol 626 ◽  
pp. A119 ◽  
Author(s):  
S. Gill ◽  
P. F. L. Maxted ◽  
J. A. Evans ◽  
D. F. Evans ◽  
J. Southworth ◽  
...  
Keyword(s):  
Binary Systems ◽  
Evolutionary Models ◽  
Mixing Length ◽  
M Dwarfs ◽  
Primary Star ◽  
Best Fitting ◽  
Low Mass ◽  
Limb Darkening ◽  
M Dwarf ◽  
Orbital Solution

Some M-dwarfs around F-/G-type stars have been measured to be hotter and larger than predicted by stellar evolution models. Inconsistencies between observations and models need to be addressed with more mass, radius, and luminosity measurements of low-mass stars to test and refine evolutionary models. Our aim is to measure the masses, radii and ages of the stars in five low-mass eclipsing binary systems discovered by the WASP survey. We used WASP photometry to establish eclipse-time ephemerides and to obtain initial estimates for the transit depth and width. Radial velocity measurements were simultaneously fitted with follow-up photometry to find the best-fitting orbital solution. This solution was combined with measurements of atmospheric parameters to interpolate evolutionary models and estimate the mass of the primary star, and the mass and radius of the M-dwarf companion. We assess how the best fitting orbital solution changes if an alternative limb-darkening law is used and quantify the systematic effects of unresolved companions. We also gauge how the best-fitting evolutionary model changes if different values are used for the mixing length parameter and helium enhancement. We report the mass and radius of five M-dwarfs and find little evidence of inflation with respect to evolutionary models. The primary stars in two systems are near the “blue hook” stage of their post sequence evolution, resulting in two possible solutions for mass and age. We find that choices in helium enhancement and mixing-length parameter can introduce an additional 3−5% uncertainty in measured M-dwarf mass. Unresolved companions can introduce an additional 3−8% uncertainty in the radius of an M-dwarf, while the choice of limb-darkening law can introduce up to an additional 2% uncertainty. The choices in orbital fitting and evolutionary models can introduce significant uncertainties in measurements of physical properties of such systems.

scholarly journals Globular clusters as laboratories for stellar evolution

2009 ◽  
Vol 5 (S266) ◽  
pp. 281-292 ◽  
Author(s):  
Márcio Catelan ◽  
Aldo A. R. Valcarce ◽  
Allen V. Sweigart
Keyword(s):  
Stellar Evolution ◽  
Globular Clusters ◽  
Helium Abundance ◽  
Multiple Populations ◽  
Abundance Patterns ◽  
Low Mass

AbstractGlobular clusters have long been considered the closest approximation to a physicist's laboratory in astrophysics, and as such a near-ideal laboratory for (low-mass) stellar evolution. However, recent observations have cast a shadow on this long-standing paradigm, suggesting the presence of multiple populations with widely different abundance patterns, and—crucially– with widely different helium abundances as well. In this review we discuss which features of the Hertzsprung–Russel diagram may be used as helium-abundance indicators, and present an overview of available constraints on the helium abundance in globular clusters.

scholarly journals On the Evolutionary History of Progenitors of EHBs and Related Binary Systems from their Observed Properties

2006 ◽  
Vol 2 (S240) ◽  
pp. 678-681
Author(s):  
V.V. Pustynski ◽  
I. Pustylnik
Keyword(s):  
Angular Momentum ◽  
Binary Systems ◽  
Mass Loss Rate ◽  
Analytical Formula ◽  
Solar Mass ◽  
Momentum Loss ◽  
Angular Momentum Loss ◽  
History Of ◽  
Low Mass ◽  
Red Giant

AbstractIt has been shown quite recently (Morales-Rueda et al. 2003) that dB stars, extreme horizontal branch (EHB) objects in high probability all belong to binary systems. We study in detail the mass and angular momentum loss from the giant progenitors of sdB stars in an attempt to clarify why binarity must be a crucial factor in producing EHB objects. Assuming that the progenitors of EHB objects belong to binaries with initial separations of a roughly a hundred solar radii and fill in their critical Roche lobes while close to the tip of red giant branch, we have found that considerable shrinkage of the orbit can be achieved due to a combined effect of angular momentum loss from the red giant and appreciable accretion on its low mass companion on the hydrodynamical timescale of the donor, resulting in formation of helium WD with masses roughly equal to a half solar mass and thus evading the common envelope stage. A simple approximative analytical formula for mass loss rate from Roche lobe filling giant donor has been proposed depending on mass, luminosity and radius of donor.

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