Binary interaction along the RGB: The Barium Star perspective

2018 ◽  
Vol 14 (S343) ◽  
pp. 394-395
Author(s):  
A. Escorza ◽  
L. Siess ◽  
D. Karinkuzhi ◽  
H. M. J. Boffin ◽  
A. Jorissen ◽  
...  
Keyword(s):  
Mass Transfer ◽  
White Dwarf ◽  
Binary Systems ◽  
Main Sequence ◽  
Binary Interaction ◽  
Evolutionary Models ◽  
Interaction Mechanisms ◽  
Second Stage ◽  
Eccentric Orbits ◽  
Additional Interaction

AbstractBarium (Ba) stars form via mass-transfer in binary systems, and can subsequently interact with their white dwarf companion in a second stage of binary interaction. We used observations of main-sequence Ba systems as input for our evolutionary models, and try to reproduce the orbits of the Ba giants. We show that to explain short and sometimes eccentric orbits, additional interaction mechanisms are needed along the RGB.

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 Binary evolution along the red giant branch with BINSTAR: The barium star perspective

2020 ◽  
Vol 639 ◽  
pp. A24 ◽  
Author(s):  
A. Escorza ◽  
L. Siess ◽  
H. Van Winckel ◽  
A. Jorissen
Keyword(s):  
White Dwarf ◽  
Binary Systems ◽  
Main Sequence ◽  
Asymptotic Giant Branch ◽  
Binary Interaction ◽  
Second Phase ◽  
Capture Process ◽  
Short Period ◽  
Binary Evolution ◽  
Red Giant

Barium (Ba), CH, and extrinsic or Tc-poor S-type stars are evolved low- and intermediate-mass stars that show enhancement of slow-neutron-capture-process elements on their surface, an indication of mass accretion from a former asymptotic giant branch companion, which is now a white dwarf (WD). Ba and CH stars can be found in the main-sequence (MS), the sub-giant, and the giant phase, while extrinsic S-type stars populate the giant branches only. As these polluted stars evolve, they might be involved in a second phase of interaction with their now white dwarf companion. In this paper, we consider systems composed of a main-sequence Ba star and a WD companion when the former evolves along the red giant branch (RGB). We want to determine if the orbital properties of the known population of Ba, CH, and S giants can be inferred from the evolution of their suspected dwarf progenitors. For this purpose, we used the BINSTAR binary evolution code and model MS+WD binary systems, considering different binary interaction mechanisms, such as a tidally enhanced wind mass loss, and a reduced circularisation efficiency. To explore their impact on the second RGB ascent, we compared the modelled orbits with the observed period and eccentricity distributions of Ba and related giants. We show that, independently of the considered mechanism, there is a strong period cut-off below which core-He burning stars should not be found in binary systems with a WD companion. This limit is shorter for more massive RGB stars and for more metal-poor systems. However, we still find a few low-mass short-period giant systems that are difficult to explain with our models, as well as two systems with very high eccentricities.

scholarly journals Two-dimensional simulations of mixing in classical novae: The effect of white dwarf composition and mass

2018 ◽  
Vol 619 ◽  
pp. A121 ◽  
Author(s):  
Jordi Casanova ◽  
Jordi José ◽  
Steven N. Shore
Keyword(s):  
White Dwarf ◽  
Binary Systems ◽  
Main Sequence ◽  
Chemical Species ◽  
Two Dimensions ◽  
Classical Novae ◽  
Nova Shells ◽  
Solar Abundances ◽  
Low Mass ◽  
Thermonuclear Runaway

Context. Classical novae are explosive phenomena that take place in stellar binary systems. They are powered by mass transfer from a low-mass main sequence star onto either a CO or ONe white dwarf. The material accumulates for 104–105 yr until ignition under degenerate conditions, resulting in a thermonuclear runaway. The nuclear energy released produces peak temperatures of ∼0.1–0.4 GK. During these events, 10−7−10−3 M⊙ enriched in intermediate-mass elements, with respect to solar abundances, are ejected into the interstellar medium. However, the origin of the large metallicity enhancements and the inhomogeneous distribution of chemical species observed in high-resolution spectra of ejected nova shells is not fully understood. Aims. Recent multidimensional simulations have demonstrated that Kelvin-Helmholtz instabilities that operate at the core-envelope interface can naturally produce self-enrichment of the accreted envelope with material from the underlying white dwarf at levels that agree with observations. However, such multidimensional simulations have been performed for a small number of cases and much of the parameter space remains unexplored. Methods. We investigated the dredge-up, driven by Kelvin-Helmholtz instabilities, for white dwarf masses in the range 0.8–1.25 M⊙ and different core compositions, that is, CO-rich and ONe-rich substrates. We present a set of five numerical simulations performed in two dimensions aimed at analyzing the possible impact of the white dwarf mass, and composition, on the metallicity enhancement and explosion characteristics. Results. At the time we stop the simulations, we observe greater mixing (∼30% higher when measured in the same conditions) and more energetic outbursts for ONe-rich substrates than for CO-rich substrates and more massive white dwarfs.

scholarly journals The Formation of Compact Objects in Binary Systems

1981 ◽  
Vol 93 ◽  
pp. 155-175 ◽  
Author(s):  
E.P.J. van den Heuvel
Keyword(s):  
Mass Transfer ◽  
Binary Systems ◽  
Compact Star ◽  
Compact Objects ◽  
Binary Interaction ◽  
X Ray ◽  
Tidal Forces ◽  
Short Period ◽  
Wide Range ◽  
X Ray Binaries

The various ways in which compact objects (neutron stars and black holes) can be formed in interacting binary systems are qualitatively outlined on the basis of the three major modes of binary interaction identified by Webbink (1980). Massive interacting binary systems (M1 ≳ 10–12 M⊙) are, after the first phase of mass transfer expected to leave as remnants:(i) compact stars in massive binary systems (mass ≳ 10 M⊙) with a wide range of orbital periods, as remnants of quasi-conservative mass transfer; these systems later evolve into massive X-ray binaries.(ii) short-period compact star binaries (P ~ 1–2 days) in which the companion may be more massive or less massive than the compact object; these systems have high runaway velocities (≳ 100 km/sec) and start out with highly eccentric orbits, which are rapidly circularized by tidal forces; they may later evolve into low-mass X-ray binaries;(iii) single runaway compact objects with space velocities of ~ 102 to 4.102 km/sec; these are expected to be the most numerous compact remnants.Compact star binaries may also form from Cataclysmic binaries or wide binaries in which an O-Ne-Mg white dwarf is driven over the Chandrasekhar limit by accretion.

scholarly journals Alone but not lonely: Observational evidence that binary interaction is always required to form hot subdwarf stars

2020 ◽  
Vol 642 ◽  
pp. A180
Author(s):  
Ingrid Pelisoli ◽  
Joris Vos ◽  
Stephan Geier ◽  
Veronika Schaffenroth ◽  
Andrzej S. Baran
Keyword(s):  
Proper Motion ◽  
Binary Systems ◽  
Main Sequence ◽  
Open Clusters ◽  
Binary Interaction ◽  
Spectral Energy ◽  
Wide Binary ◽  
Single Star ◽  
Rotation Rates ◽  
Hot Subdwarfs

Context. Hot subdwarfs are core-helium burning stars that show lower masses and higher temperatures than canonical horizontal branch stars. They are believed to be formed when a red giant suffers an extreme mass-loss episode. Binary interaction is suggested to be the main formation channel, but the high fraction of apparently single hot subdwarfs (up to 30%) has prompted single star formation scenarios to be proposed. Aims. We investigate the possibility that hot subdwarfs could form without interaction by studying wide binary systems. If single formation scenarios were possible, there should be hot subdwarfs in wide binaries that have undergone no interaction. Methods. Angular momentum accretion during interaction is predicted to cause the hot subdwarf companion to spin up to the critical velocity. The effect of this should still be observable given the timescales of the hot subdwarf phase. To study the rotation rates of companions, we have analysed light curves from the Transiting Exoplanet Survey Satellite for all known hot subdwarfs showing composite spectral energy distributions indicating the presence of a main sequence wide binary companion. If formation without interaction were possible, that would also imply the existence of hot subdwarfs in very wide binaries that are not predicted to interact. To identify such systems, we have searched for common proper motion companions with projected orbital distances of up to 0.1 pc to all known spectroscopically confirmed hot subdwarfs using Gaia DR2 astrometry. Results. We find that the companions in composite hot subdwarfs show short rotation periods when compared to field main sequence stars. They display a triangular-shaped distribution with a peak around 2.5 days, similar to what is observed for young open clusters. We also report a shortage of hot subdwarfs with candidate common proper motion companions. We identify only 16 candidates after probing 2938 hot subdwarfs with good astrometry. Out of those, at least six seem to be hierarchical triple systems, in which the hot subdwarf is part of an inner binary. Conclusions. The observed distribution of rotation rates for the companions in known wide hot subdwarf binaries provides evidence of previous interaction causing spin-up. Additionally, there is a shortage of hot subdwarfs in common proper motion pairs, considering the frequency of such systems among progenitors. These results suggest that binary interaction is always required for the formation of hot subdwarfs.

scholarly journals Massive donors in interacting binaries: effect of metallicity

2020 ◽  
Vol 638 ◽  
pp. A55 ◽  
Author(s):  
Jakub Klencki ◽  
Gijs Nelemans ◽  
Alina G. Istrate ◽  
Onno Pols
Keyword(s):  
Mass Transfer ◽  
Parameter Space ◽  
Binary Systems ◽  
Main Sequence ◽  
Massive Stars ◽  
First Episode ◽  
Sequence Evolution ◽  
Radial Expansion ◽  
Solar Metallicity ◽  
Order Of Magnitude

Metallicity is known to significantly affect the radial expansion of a massive star: the lower the metallicity, the more compact the star, especially during its post-main sequence evolution. Our goal is to study this effect in the context of binary evolution. Using the stellar-evolution code MESA, we computed evolutionary tracks of massive stars at six different metallicities between 1.0 Z⊙ and 0.01 Z⊙. We explored variations of factors known to affect the radial expansion of massive stars (e.g., semiconvection, overshooting, or rotation). Using observational constraints, we find support for an evolution in which already at a metallicity Z ≈ 0.2 Z⊙ massive stars remain relatively compact (∼100 R⊙) during the Hertzprung-gap (HG) phase and most of their expansion occurs during core-helium burning (CHeB). Consequently, we show that metallicity has a strong influence on the type of mass transfer evolution in binary systems. At solar metallicity, a case-B mass transfer is initiated shortly after the end of the main sequence, and a giant donor is almost always a rapidly expanding HG star. However, at lower metallicity, the parameter space for mass transfer from a more evolved, slowly expanding CHeB star increases dramatically. This means that envelope stripping and formation of helium stars in low-metallicity environments occurs later in the evolution of the donor, implying a shorter duration of the Wolf-Rayet phase (even by an order of magnitude) and higher final core masses. This metallicity effect is independent of the effect of metallicity-dependent stellar winds. At metallicities Z ≤ 0.04 Z⊙, a significant fraction of massive stars in binaries with periods longer than 100 days engages in the first episode of mass transfer very late into their evolution, when they already have a well-developed CO core. The remaining lifetime (≲104 yr) is unlikely to be long enough to strip the entire H-rich envelope. Cases of unstable mass transfer leading to a merger would produce CO cores that spin fast at the moment of collapse. We find that the parameter space for mass transfer from massive donors (> 40 M⊙) with outer convective envelopes is extremely small or even nonexistent. We briefly discuss this finding in the context of the formation of binary black hole mergers.

scholarly journals White dwarf deflagrations for Type Iax supernovae: polarisation signatures from the explosion and companion interaction

2020 ◽  
Vol 635 ◽  
pp. A179 ◽  
Author(s):  
M. Bulla ◽  
Z.-W. Liu ◽  
F. K. Röpke ◽  
S. A. Sim ◽  
M. Fink ◽  
...  
Keyword(s):  
White Dwarf ◽  
Reasonable Agreement ◽  
Binary Systems ◽  
3D Model ◽  
Main Sequence ◽  
Interaction Model ◽  
Supernova Explosion ◽  
Viewing Angle ◽  
Companion Star ◽  
Intrinsic Signal

Growing evidence suggests that Type Iax supernovae might be the result of thermonuclear deflagrations of Chandrasekhar-mass white dwarfs in binary systems. We carry out Monte Carlo radiative transfer simulations and predict spectropolarimetric features originating from the supernova explosion and subsequent ejecta interaction with the companion star. Specifically, we calculate viewing-angle dependent flux and polarisation spectra for a 3D model simulating the deflagration of a Chandrasekhar-mass white dwarf and, for a second model, simulating the ejecta interaction with a main-sequence star. We find that the intrinsic signal is weakly polarised and only mildly viewing-angle dependent, owing to the overall spherical symmetry of the explosion and the depolarising contribution of iron-group elements dominating the ejecta composition. The interaction with the companion star carves out a cavity in the ejecta and produces a detectable, but modest signal that is significant only at relatively blue wavelengths (≲5000 Å). In particular, increasingly fainter and redder spectra are predicted for observer orientations further from the cavity, while a modest polarisation signal P ~ 0.2 per cent is found at blue wavelengths for orientations 30° and 45° away from the cavity. We find a reasonable agreement between the interaction model viewed from these orientations and spectropolarimetric data of SN 2005hk and interpret the maximum-light polarisation signal seen at blue wavelengths for this event as a possible signature of the ejecta–companion interaction. We encourage further polarimetric observations of SNe Iax to test whether our results can be extended and generalised to the whole SN Iax class.

scholarly journals The Temperatures of White Dwarfs in Accreting Binaries

1989 ◽  
Vol 114 ◽  
pp. 92-96 ◽  
Author(s):  
Paula Szkody ◽  
Edward M. Sion
Keyword(s):  
Mass Transfer ◽  
Energy Distribution ◽  
White Dwarf ◽  
White Dwarfs ◽  
Binary Systems ◽  
Spectral Lines ◽  
Emission Lines ◽  
Minor Amount ◽  
Dwarf Novae ◽  
Optical Flux

Through the use of accreting binary systems, it is possible to study the effects of the deposition of matter and energy on the surface of a white dwarf. The observed atmospheric properties of composition and temperature obtained from direct observation of the spectral lines and the continuum flux can be used to compare with those of single white dwarfs to understand the consequences of mass accretion on binary evolution.Cataclysmic variables provide one of the best targets for this type of study because a) the primaries are all white dwarfs b) the level and the timescale of the accretion cover a large range from the high rate, relatively steady novalike accretors to the dwarf novae systems which are modulated on short timescales in a quasi-periodic manner. Unfortunately, due to the mass transfer process, an accretion disk builds up to the point where its radiation overwhelms the white dwarf light in most cases. Thus, to study the effects on the stellar primary, systems must be found which have low mass transfer rates (generally the short orbital period systems (Patterson 1984)) and/or high inclinations (since most of the disk flux emerges perpendicular to the plane of the disk). The best identification of the white dwarf emerges from IUE spectra which show a broad Lyman α absorption profile (in contrast to the normal emission lines from a disk at quiescence). The shape of this profile provides a sensitive indicator of the temperature and gravity. In some cases, broad absorption lines are also evident in the optical Balmer lines, although the broad emission lines from the disk usually make these difficult to detect. The steeply falling flux distribution of a white dwarf throughout the optical region, combined with a flat disk distribution usually means that the white dwarf contributes a minor amount to the optical flux. However, in the ultraviolet, the rising energy distribution of the white dwarf easily dominates the falling energy distribution of a low accretion rate disk (Mateo and Szkody 1984). White dwarfs are generally acknowledged to be prominent in the dwarf novae U Gem (Panek and Holm 1984), VW Hyi (Mateo and Szkody 1984) and Z Cha (Marsh, Horne and Shipman 1987) and suggested in EK TrA and WZ Sge (Verbunt 1987). In addition, the white dwarf has been seen in some novalike systems which sporadically turn off their mass transfer, (resulting in the disappearance of most of the disk and the resulting appearance of the white dwarf). This has been the case in TT Ari (Shafter et al. 1985) and some limits have been determined for MV Lyr (Szkody and Downes 1982) and V794 Aql (Szkody, Downes and Mateo 1988). Several magnetic white dwarfs have also been seen when the mass transfer ceases in the AM Her systems (summarized in Szkody, Downes and Mateo 1988).

scholarly journals A Gentle Process for the Formation of Algols

1989 ◽  
Vol 107 ◽  
pp. 369-369
Author(s):  
C. A. Tout ◽  
P. P. Eggleton
Keyword(s):  
Mass Transfer ◽  
Magnetic Fields ◽  
Mass Loss ◽  
White Dwarf ◽  
Binary Systems ◽  
Roche Lobe ◽  
Close Binary ◽  
Red Giants ◽  
Convective Envelope ◽  
Mass Ratios

AbstractThis work is concerned with binary systems that we call ‘moderately close’. These are systems in which the primary (by which we mean the initially more massive star) fills its Roche lobe when it is on the giant branch with a deep convective envelope but before helium ignition (late case B). We find that if the mass ratio q(= M1/M2) < qCrit = 0.7 when the primary fills its Roche lobe positive feedback will lead to a rapid hydrodynamic phase of mass transfer which will probably lead to common envelope evolution and thence to either coalescence or possibly to a close binary in a planetary nebula. Although most Algols have probably filled their Roche lobes before evolving off the main-sequence we find that some could not have and are therefore ‘moderately close’. Since rapid overflow is unlikely to lead to an Algol-like system there must be some way of avoiding it. The most likely possibility is that the primary can lose sufficient mass to reduce q below qcrit before overflow begins. Ordinary mass loss rates are insufficient but evidence that enhanced mass loss does take place is provided by RS CVn systems that have inverted mass ratios but have not yet begun mass transfer. We postulate that the cause of enhanced mass loss lies in the heating of the corona by by magnetic fields maintained by an α-ω dynamo which is enhanced by tidal effects associated with corotation. In order to model the the effects of enhanced mass loss we ignore the details and adopt an empirical approach calibrating a simple formula with the RS CVn system Z Her. Using further empirical relations (deduced from detailed stellar models) that describe the evolution of red giants we have investigated the effect on a large number of systems of various initial mass ratios and periods. These are notable in that some systems can now enter a much gentler Algol-like overflow phase and others are prevented from transferring mass altogether. We have also investigated the effects of enhanced angular momentum loss induced by corotation of the wind in the strong magnetic fields and consider this in relation to observed period changes. We find that a typical ‘moderately close’ Algol-like system evolves through an RS CVn like system and then possibly a symbiotic state before becoming an Algol and then goes on through a red giant-white dwarf state which may become symbiotic before ending up as a double white dwarf system in either a close or wide orbit depending on how much mass is lost before the secondary fills its Roche lobe.

scholarly journals Evolution of Intermediate Mass Close Binaries

1980 ◽  
Vol 88 ◽  
pp. 109-114
Author(s):  
Th.J. Van Der Linden
Keyword(s):  
Mass Transfer ◽  
Binary Systems ◽  
Main Sequence ◽  
Mass Transfer Rate ◽  
Primary Component ◽  
Close Binary ◽  
Close Binaries ◽  
Transfer Phase ◽  
Helium Burning ◽  
Helium Star

Numerical simulations of close binary evolution were performed for five binary systems, using a newly developed evolutionary program. The systems have masses 3+2, 4+3.2, 6+4, 9+6, 12+8 M⊙ and periods 2d, 1d78, 3d, 4d, 5d respectively. The primary component was followed from the zero-age main sequence through the mass transfer phase to core-helium burning. Special care was given to the self-consistent determination of the mass transfer rate and the detailed treatment of composition changes. After the mass transfer phase the resulting systems consist of a main sequence star with a helium star companion of mass 0.36, 0.46, 0.82, 1.48, 2.30 M⊙ for the five systems respectively. Interesting “thermal pulses” were found in the 3+2 M⊙ system at the onset of helium burning.

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