scholarly journals Internal circulation in tidally locked massive binary stars: Consequences for double black hole formation

2020 ◽  
Vol 641 ◽  
pp. A86
Author(s):  
B. Hastings ◽  
N. Langer ◽  
G. Koenigsberger
Keyword(s):  
Black Hole ◽  
Steady State ◽  
Binary Stars ◽  
Binary Star ◽  
Internal Circulation ◽  
Helium Stars ◽  
Mass Ratios ◽  
Circulation Velocity ◽  
Orbital Periods ◽  
Rotating Star

Context. Steady-state currents, so-called Eddington–Sweet circulation, result in the mixing of chemical elements in rotating stars, and in extreme cases lead to a homogeneous composition. Such circulation currents are also predicted in tidally deformed binary stars, which are thought to be progenitors of double black-hole merger events. Aims. This work aims to quantitatively characterise the steady-state circulation currents in components of a tidally locked binary system and to explore the effects of such currents on numerical models. Methods. Previous results describing the circulation velocity in a single rotating star and a tidally and rotationally distorted binary star are used to deduce a new prescription for the internal circulation in tidally locked binaries. We explore the effect of this prescription numerically with a detailed stellar evolution code for binary systems with initial orbital periods between 0.5 and 2.0 days, primary masses between 25 and 100 M⊙ and initial mass-ratios qi = 0.5, 0.7, 0.9, 1.0 at metallicity Z = Z⊙/50. Results. When comparing circulation velocities in the radial direction for the cases of a single rotating star and a binary star, it is found that the average circulation velocity in the binary star may be described as an enhancement to the circulation velocity in a single rotating star. This velocity enhancement is a simple function depending on the masses of the binary components and amounts to a factor of approximately two when the components have equal masses. After applying this enhancement to stellar models, it is found that the formation of double helium stars through efficient mixing occurs for systems with higher initial orbital periods, lower primary masses and lower mass ratios, compared to the standard circulation scenario. Taking into account appropriate distributions for primary mass, initial period and mass ratio, models with enhanced mixing predict 2.4 times more double helium stars being produced in the parameter space than models without. Conclusions. We conclude that the effects of companion-induced circulation have strong implications for the formation of close binary black holes through the chemically homogeneous evolution channel. Not only do the predicted detection rates increase but double black-hole systems with mass ratios as low as 0.8 may be formed when companion-induced circulation is taken into account.

scholarly journals Origin of the orbital period change in contact binary stars

2019 ◽  
Vol 28 (06) ◽  
pp. 1950044 ◽  
Author(s):  
V. V. Sargsyan ◽  
H. Lenske ◽  
G. G. Adamian ◽  
N. V. Antonenko
Keyword(s):  
Orbital Period ◽  
Binary Stars ◽  
Binary Systems ◽  
Binary Star ◽  
Period Change ◽  
Mass Asymmetry ◽  
Contact Binary Stars ◽  
Contact Binary ◽  
Energy Formula ◽  
Orbital Periods

The evolution of contact binary star systems in mass asymmetry (transfer) coordinate is considered. The orbital period changes are explained by an evolution in mass asymmetry towards the symmetry (symmetrization of binary system). It is predicted that decreasing and increasing orbital periods are related, respectively, with the nonoverlapping and overlapping stage of the binary star during its symmetrization. A huge amount of energy [Formula: see text][Formula: see text]J is converted from the potential energy into internal energy of the stars during the symmetrization. As shown, the merger of stars in the binary systems, including KIC 9832227, is energetically an unfavorable process. The sensitivity of the calculated results to the values of total mass and orbital angular momentum is analyzed.

scholarly journals The fate of binary stars hosting planets upon interaction with Sgr A* black hole

2020 ◽  
Vol 496 (2) ◽  
pp. 1545-1553
Author(s):  
R Capuzzo-Dolcetta ◽  
N Davari
Keyword(s):  
Black Hole ◽  
High Precision ◽  
Binary Stars ◽  
Binary Star ◽  
Planetary Systems ◽  
The Other ◽  
Supermassive Black Hole ◽  
Massive Object ◽  
Close Interaction ◽  
Sgr A

ABSTRACT Our Galaxy hosts a very massive object at its centre, often referred to as the supermassive black hole Sgr A*. Its gravitational tidal field is so intense that it can strip apart a binary star passing its vicinity and accelerate one of the components of the binary as hypervelocity star (HVS) and grab the other star as S-star. Taking into consideration that many binary star systems are known to host planets, in this paper we aim to broaden the study of the close interaction of binary stars and their planetary systems with Sgr A* massive object. Results are obtained via a high-precision N-body code including post-Newtonian approximation. We quantify the likelihood of capture and ejection of stars and planets after interaction with Sgr A*, finding that the fraction of stars captured around it is about three times that of the planets (∼49.4 per cent versus ∼14.5 per cent) and the fraction of hypervelocity planet ejection is about twice that of HVSs (∼21.7 per cent versus ∼9.0 per cent). The actual possibility of observational counterparts deserves further investigation.

scholarly journals Most EL CVn systems are inner binaries of hierarchical triples

2020 ◽  
Vol 499 (1) ◽  
pp. L121-L125
Author(s):  
F Lagos ◽  
M R Schreiber ◽  
S G Parsons ◽  
B T Gänsicke ◽  
N Godoy
Keyword(s):  
Binary Stars ◽  
Main Sequence ◽  
Binary Star ◽  
Close Binary ◽  
Compact Binary ◽  
Test Models ◽  
Close Binary Stars ◽  
Orbital Periods ◽  
Binary Evolution ◽  
Modern Astronomy

ABSTRACT In spite of their importance for modern astronomy, we do not fully understand how close binary stars containing at least one white dwarf form from main-sequence binary stars. The discovery of EL CVn binaries, close pre-white dwarfs with A/F main-sequence star companions, offers now the unique possibility to test models of close compact binary star formation. Binary evolution theories predict that these EL CVn stars descend from very close main-sequence binaries with orbital periods shorter than 3 d. If this is correct, nearly all EL CVn stars should be inner binaries of hierarchical triples because more than 95 per cent of very close main-sequence binaries (the alleged progenitor systems) are found to be hierarchical triples. We here present SPHERE/IRDIS observations of five EL CVn binaries, finding in all of them tertiary objects, as predicted. We conclude that EL CVn systems are inner binaries of hierarchical triples and indeed descend from very close main-sequence binaries that experience stable mass transfer.

Searching for Long-Period Binary Central Stars of Planetary Nebulae with SALT HRS

2017 ◽  
Vol 14 (S339) ◽  
pp. 330-330
Author(s):  
B. Miszalski ◽  
R. Manick ◽  
J. Mikołajewska ◽  
K. Iłkiewicz ◽  
D. Kamath ◽  
...  
Keyword(s):  
Binary Stars ◽  
Binary Systems ◽  
Binary Star ◽  
Planetary Nebulae ◽  
Close Binary ◽  
Close Binaries ◽  
Long Period ◽  
Orbital Periods ◽  
The Many ◽  
Made In

AbstractIn the last decade great strides have been made in understanding the role of binary stars in the evolution and shaping of planetary nebulæ (PNe). Observational efforts have mainly focused on finding close binaries with orbital periods of 1 day or less. Those close binary systems make up around 1 in 5 PNe, and constitute the youngest accessible window into the aftermath of the critical and unobserved common-envelope (CE) phase of binary-star evolution. The poster focused on our recent work with the High Resolution Spectrograph (HRS) on the Southern African Large Telescope (SALT) to search for long-period binaries in PNe. Considerably less is known about such long-period binaries with orbital periods of weeks to years, but they may be fundamental to improving CE population synthesis models and for determining the total binary fraction of PNe. The queue-mode operation of SALT and the excellent sensitivity and stability of HRS (which is enclosed in a vacuum tank) are ideally suited to detecting binaries with low radial-velocity amplitudes over the expected timescales of weeks to years. Many exciting new discoveries about binaries have already been made in this newly-accessible southern horizon in time-domain astronomy thanks to the many unique advantages of SALT.

Mass Ratios in Wide Binary Stars

1997 ◽  
Vol 485 (2) ◽  
pp. 785-788 ◽  
Author(s):  
Mauri J. Valtonen
Keyword(s):  
Binary Stars ◽  
Wide Binary ◽  
Mass Ratios

scholarly journals The symbiotics as binary stars

1982 ◽  
Vol 70 ◽  
pp. 231-251
Author(s):  
Mirek J. Plavec
Keyword(s):  
Mass Transfer ◽  
Binary Stars ◽  
Binary Star ◽  
Evolutionary Stage ◽  
Cool Component ◽  
Second Stage ◽  
Star Evolution ◽  
Red Giant ◽  
Helium Star ◽  
Central Stars

AbstractSymbiotic stars have become an important testing ground of various theories of binary star evolution. Several physically different models can explain them, but in each case certain fairly restrictive conditions must be met, so if we manage to identify a definite object with a model, it will tell us a lot about the structure and evolutionary stage of the stars involved. I envisage at least three models that can give us a symbiotic object: I have called them, respectively, the PN symbiotic, the Algol symbiotic, and the novalike symbiotic. Their properties are briefly discussed. The most promising model is one of a binary system in the second stage of mass transfer, actually at the beginning of it: The cool component is a red giant ascending the asymptotic branch, expanding but not yet filling its critical lobe. The hot star is a subdwarf located in the same region of the Hertzsprung-Russell diagram as the central stars of planetary nebulae. It may be closely related to them, or it may be a helium star, actually a remnant of an Algol primary which underwent the first stage of mass transfer. In these cases, accretion on this star may not play a significant role (PN symbiotic).

scholarly journals A binary star formation mechanism through the fragmentation of prolate dense cores rotating end over end

1991 ◽  
Vol 147 ◽  
pp. 526-528
Author(s):  
Hans Zinnecker
Keyword(s):  
Star Formation ◽  
Formation Mechanism ◽  
Binary Stars ◽  
Binary Star ◽  
Initial Structure ◽  
Eccentric Orbit ◽  
Dense Cores ◽  
Molecular Core ◽  
Low Mass

I propose and briefly elaborate on a major new mechanism for the formation of wide, low-mass binary stars: the fragmentation of a collapsing, initially elongated dense molecular core rotating end over end. This initial structure will develop into two independent gravitationally bound stellar condensations orbiting each other in a rather eccentric orbit.

scholarly journals Radio Emitting X-Ray Binary Stars

1996 ◽  
Vol 158 ◽  
pp. 371-374
Author(s):  
R. E. Spencer
Keyword(s):  
Black Hole ◽  
Neutron Star ◽  
Radio Emission ◽  
Binary Stars ◽  
X Ray ◽  
Ss 433 ◽  
Normal Star ◽  
Large Numbers ◽  
X Ray Binaries

Some of the most astrophysically interesting objects are found among the radio-emitting X-ray binary stars (REXRB). The class includes the well-studied objects such as SS 433, Cyg X-3 and Sco X-1. The recent discoveries of relativistic ejection of radio knots in the X-ray transients 1915+105 (Mirabel & Rodriguez 1994) and 1655–40 (Hjellming & Rupen 1995) well illustrate the extreme nature of some of these objects.X-ray binaries are semi-detached binary stars in which matter is transfered from a more or less normal star onto a neutron star or black hole. X-ray satellites have detected large numbers of these objects (193 in a recent catalogue by van Paradijs 1995). However only a small fraction of these are known to have radio emission (e.g. Hjellming 1988).

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