scholarly journals Fast rotating stars resulting from binary evolution will often appear to be single

2010 ◽  
Vol 6 (S272) ◽  
pp. 531-532 ◽  
Author(s):  
Selma E. de Mink ◽  
Norbert Langer ◽  
Robert G. Izzard
Keyword(s):  
Binary System ◽  
Binary Systems ◽  
Large Fraction ◽  
Supernova Explosion ◽  
Binary Interaction ◽  
Close Binaries ◽  
Rotating Stars ◽  
Single Star ◽  
Rapidly Rotating Stars ◽  
Fast Rotating

AbstractRapidly rotating stars are readily produced in binary systems. An accreting star in a binary system can be spun up by mass accretion and quickly approach the break-up limit. Mergers between two stars in a binary are expected to result in massive, fast rotating stars. These rapid rotators may appear as Be or Oe stars or at low metallicity they may be progenitors of long gamma-ray bursts.Given the high frequency of massive stars in close binaries it seems likely that a large fraction of rapidly rotating stars result from binary interaction. It is not straightforward to distinguish a a fast rotator that was born as a rapidly rotating single star from a fast rotator that resulted from some kind of binary interaction. Rapidly rotating stars resulting from binary interaction will often appear to be single because the companion tends to be a low mass, low luminosity star in a wide orbit. Alternatively, they became single stars after a merger or disruption of the binary system during the supernova explosion of the primary.The absence of evidence for a companion does not guarantee that the system did not experience binary interaction in the past. If binary interaction is one of the main causes of high stellar rotation rates, the binary fraction is expected to be smaller among fast rotators. How this prediction depend on uncertainties in the physics of the binary interactions requires further investigation.

scholarly journals Origin of Binary Systems

1992 ◽  
Vol 151 ◽  
pp. 9-19
Author(s):  
Peter Bodenheimer
Keyword(s):  
Angular Momentum ◽  
Binary Systems ◽  
Theoretical Calculations ◽  
Pressure Effects ◽  
Close Binaries ◽  
Rotating Stars ◽  
Multiple Systems ◽  
The Individual ◽  
Protostellar Collapse ◽  
Three Body

Recent observational studies of the properties of binary systems among young stars indicate that the majority of binaries are formed very early in the history of a star, perhaps during the protostellar collapse. Major observational facts to be explained include the overall binary frequency, the non-negligible occurrence of multiple systems, and the distributions of period, eccentricity, and mass ratio among the individual binaries. Theoretical calculations of the collapse of rotating protostars during the isothermal phase indicate instability to fragmentation into multiple systems. This process in general produces systems with periods greater than a few hundred years, although somewhat shorter periods are possible. Fragmentation during later, optically thick, phases of collapse tends to be suppressed by pressure effects. Therefore, major theoretical problems remain concerning the origin of close binaries. Fission of rapidly rotating stars, tidal capture, and three-body capture have been shown to be improbable mechanisms for formation of close binaries. Mechanisms currently under study include gravitational instabilities in disks, orbital interactions and disk-induced captures in fragmented multiple systems, hierarchical fragmentation, and orbital decay of long-period systems. Single stars, on the other hand, could result by escape from multiple systems or by the collapse of clouds of low angular momentum, coupled with angular momentum transport after disk formation.

Oscillations of Fast Rotating Stars: p-Modes in Centrifugally Flattened Polytropes

2004 ◽  
Vol 215 ◽  
pp. 414-415 ◽  
Author(s):  
F. Lignières ◽  
M. Rieutord
Keyword(s):  
Numerical Method ◽  
Centrifugal Force ◽  
Perturbation Methods ◽  
Mathematical Formalism ◽  
Rotating Stars ◽  
Oscillation Modes ◽  
Rapidly Rotating Stars ◽  
Fast Rotating

Oscillation modes of rapidly rotating stars have not yet been calculated with precision, rotational effects being generally approximated by perturbation methods. We developed a mathematical formalism and a numerical method which fully account for the deformation of the star by the centrifugal force. The method has been first tested in the case of Maclaurin spheroids and then applied to uniformly rotating polytropic stars.

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 Coronal loops and their modeling

1996 ◽  
Vol 176 ◽  
pp. 433-448 ◽  
Author(s):  
G.H.J. Van Den Oord ◽  
F. Zuccarello
Keyword(s):  
Boundary Conditions ◽  
Heat Input ◽  
Binary Systems ◽  
Phase Plane ◽  
Emission Measure ◽  
Coronal Loops ◽  
Rotating Stars ◽  
Differential Emission Measure ◽  
Loop Expansion ◽  
Rapidly Rotating Stars

We discuss the theory of quasi-static coronal loops, introducing a phase plane representation to study loop solutions independently of specific boundary conditions. Emphasis is put on the effects of loop expansion, heat input and gravitational stratification on the differential emission measure, and on the intrinsic limitations of spectroscopic observations for deriving loop parameters. We show that certain classes of published loop solutions cannot actually exist. For expanding loops new classes of loop solutions, with rather special properties, are presented. Special attention is paid to loops in binary systems and on rapidly rotating stars.

scholarly journals Structures of Binary Star Coronae

2004 ◽  
Vol 219 ◽  
pp. 199-210
Author(s):  
Nancy S. Brickhouse
Keyword(s):  
Binary Systems ◽  
Binary Star ◽  
Magnetic Loop ◽  
Close Binaries ◽  
Coronal Emission ◽  
Single Star ◽  
X Ray ◽  
Radio Studies ◽  
Show Evidence ◽  
Contact Binaries

Stellar coronae in binary star systems offer both a puzzle and an opportunity. We might expect that large magnetic loop structures on close binaries, such as RS CVn systems and contact binaries, would show evidence for interactions between the stars. While some radio studies support this scenario, there is surprisingly little evidence from EUV and X-ray observations for differences between binary and single star systems. Meanwhile, the binary systems offer observational opportunities through rotational modulation and eclipses of flaring and non-flaring regions. Localizing the sources of coronal emission is key to making the magnetic connection to the underlying photosphere. We discuss the structure of stellar coronae from the perspective of studies of binary systems.

scholarly journals The Spectral Distribution of Be/X-ray Transients Implies Supernova Kicks

2000 ◽  
Vol 175 ◽  
pp. 709-712
Author(s):  
Ignacio Negueruela
Keyword(s):  
Mass Transfer ◽  
Binary System ◽  
Spectral Distribution ◽  
Alternative Model ◽  
Large Fraction ◽  
Supernova Explosion ◽  
X Ray ◽  
Massive Component ◽  
X Ray Binaries ◽  
Orbital Solution

AbstractBe/X-ray binaries are generally assumed to have formed as the result of the evolution of moderately massive binaries in which mass is transferred semi-conservatively from the originally more massive component on to its companion. An alternative model proposes a binary system with a very massive component which loses a large fraction of its mass via very unconservative mass transfer. This scenario allows the formation of Be/X-ray binaries without requiring an asymmetric supernova explosion. We show that the observed properties of most Be/X-ray binaries for which an orbital solution has been found are incompatible with this model.

scholarly journals Is our Sun a Singleton?

2007 ◽  
Vol 3 (S246) ◽  
pp. 273-274
Author(s):  
D. Malmberg ◽  
M. B. Davies ◽  
J. E. Chambers ◽  
F. De Angeli ◽  
R. P. Church ◽  
...  
Keyword(s):  
Binary System ◽  
Solar System ◽  
Planetary System ◽  
Large Fraction ◽  
Planetary Systems ◽  
Number Density ◽  
Single Star ◽  
Close Encounters ◽  
Eccentric Orbits ◽  
Exoplanet Systems

AbstractMost stars are formed in a cluster or association, where the number density of stars can be high. This means that a large fraction of initially-single stars will undergo close encounters with other stars and/or exchange into binaries. We describe how such close encounters and exchange encounters can affect the properties of a planetary system around a single star. We define a singleton as a single star which has never suffered close encounters with other stars or spent time within a binary system. It may be that planetary systems similar to our own solar system can only survive around singletons. Close encounters or the presence of a stellar companion will perturb the planetary system, often leaving planets on tighter and more eccentric orbits. Thus planetary systems which initially resembled our own solar system may later more closely resemble some of the observed exoplanet systems.

scholarly journals Late Stages of Close Binary Systems

1976 ◽  
Vol 73 ◽  
pp. 35-61 ◽  
Author(s):  
E. P. J. Van Den Heuvel
Keyword(s):  
Angular Momentum ◽  
Mass Exchange ◽  
Binary Systems ◽  
Main Sequence ◽  
Supernova Explosion ◽  
Compact Stars ◽  
Close Binary ◽  
Close Binaries ◽  
X Ray ◽  
Loss Of Mass

The expected final evolution of massive close binaries (CB) in case B is reviewed. Primary stars with masses ≳ 12–15 M⊙ are, after loosing most of their envelope by mass exchange, expected to explode as supernovae, leaving behind a neutron star or a black hole.Conservative close binary evolution (i.e. without a major loss of mass and angular momentum from the system during the first stage of mass transfer) is expected to occur if the initial mass ratio q0 = M20/M10 is ≳ 0.3. In this case the primary star will be the less massive component when it explodes, and the system is almost never disrupted by the explosion. The explosion is followed by a long-lasting quiet stage (106–107 yr) when the system consists of a massive main-sequence star and an inactive compact companion. After the secondary has left the main-sequence and becomes a blue supergiant with a strong stellar wind, the system becomes a massive X-ray binary for a short while (2–5 × 104 yr).The numbers of Wolf-Rayet binaries and massive X-ray binaries observed within 3 kpc of the Sun are in reasonable agreement with the numbers expected on the basis of conservative CB evolution, which implies that several thousands of massive main-sequence stars with a quiet compact companion should exist in the Galaxy. About a dozen of these systems must be present among the stars visible to the naked eye. During the second stage of mass exchange, large loss of mass and angular momentum from the system is expected, leading to a rapid shrinking of the orbit. The supernova explosion of the secondary will in most cases disrupt the system. If it remains bound, the final system will consist of two compact stars and may resemble the binary pulsar PSR 1913 + 16.In systems with q0 ≲ 0.2–0.3 large mass loss from the system is expected during the first stage of mass exchange. The exploding primary will then be more massive than its unevolved companion and the first supernova explosion disrupts the system in most cases. In the rare cases that it remains bound, the system will have a large runaway velocity and, after a very long (108–109 yr) inactive stage evolves into a low-mass X-ray binary, possibly resembling Her X-1.

scholarly journals Chemical abundances of fast-rotating OB stars

2014 ◽  
Vol 9 (S307) ◽  
pp. 94-95
Author(s):  
Constantin Cazorla ◽  
Thierry Morel ◽  
Yaël Nazé ◽  
Gregor Rauw
Keyword(s):  
Massive Stars ◽  
Evolutionary Models ◽  
Rotating Stars ◽  
Chemical Abundances ◽  
Single Star ◽  
Ob Stars ◽  
Detailed Surface ◽  
Normal Nitrogen ◽  
First Time ◽  
Fast Rotating

AbstractFast rotation in massive stars is predicted to induce mixing in their interior, but a population of fast-rotating stars with normal nitrogen abundances at their surface has recently been revealed (Hunter et al.2009; Brott et al.2011, but see Maeder et al.2014). However, as the binary fraction of these stars is unknown, no definitive statements about the ability of single-star evolutionary models including rotation to reproduce these observations can be made. Our work combines for the first time a detailed surface abundance analysis with a radial-velocity monitoring for a sample of bright, fast-rotating Galactic OB stars to put strong constraints on stellar evolutionary and interior models.

scholarly journals Towards a more complete sample of binary central stars of planetary nebulae with Gaia

2021 ◽  
Vol 648 ◽  
pp. A95
Author(s):  
N. Chornay ◽  
N. A. Walton ◽  
D. Jones ◽  
H. M. J. Boffin ◽  
M. Rejkuba ◽  
...  
Keyword(s):  
Binary Systems ◽  
Large Fraction ◽  
Planetary Nebulae ◽  
Close Binary ◽  
Close Binaries ◽  
Photometric Variability ◽  
Long Time ◽  
Using Data ◽  
Central Stars

Context. Many if not most planetary nebulae (PNe) are now thought to be the outcome of binary evolutionary scenarios. However, only a few percent of the PNe in the Milky Way are known to host binary systems. The high-precision repeated observing and long time baseline of Gaia make it well suited for detecting new close binaries through photometric variability. Aims. We aim to find new close binary central stars of PNe (CSPNe) using data from the Gaia mission, building towards a statistically significant sample of post-common envelope, close binary CSPNe. Methods. As the vast majority of Gaia sources do not have published epoch photometry, we used the uncertainty in the mean photometry as a proxy for determining the variability of our CSPN sample in the second Gaia data release. We derived a quantity that expresses the significance of the variability, and considered what is necessary to build a clean sample of genuine variable sources. Results. Our selection recovers a large fraction of the known close binary CSPN population, while other CSPNe lying in the same region of the parameter space represent a promising set of targets for ground-based confirmatory follow-up observations. Gaia epoch photometry for four of the newly identified variable sources confirms that the variability is genuine and consistent with binarity.

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