scholarly journals On the Origin of the Abundance Anomalies in IK Peg

1996 ◽  
Vol 158 ◽  
pp. 461-462
Author(s):  
B. Smalley ◽  
K.C. Smith ◽  
D. Wonnacott
Keyword(s):  
Mass Transfer ◽  
Binary System ◽  
White Dwarf ◽  
Small Amplitude ◽  
Diffusion Processes ◽  
Type Star ◽  
Common Envelope ◽  
Radiative Diffusion ◽  
The Common ◽  
Abundance Anomalies

AbstractIK Peg is a binary system comprising a pulsating A-type star in orbit with a massive white dwarf. A detailed abundance analysis of IK Peg A has been performed. It is found that the Ca and Sc abundances are approximately solar, and the Fe-group elements slightly enhanced. IK Peg is not a classical Am star but the results are not inconsistent with its spectroscopic classification as a marginal Am star. An excess of Ba and Sr are found. These anomalies could be explained by radiative diffusion processes operating in the atmosphere of IK Peg A, even though it is undergoing small-amplitude pulsations. Alternatively, since the companion is a massive white dwarf, these anomalies could be the result of mass transfer during the common envelope phase of the binary system’s evolution.

scholarly journals Progress of Common Envelope Evolution

1989 ◽  
Vol 8 ◽  
pp. 155-159
Author(s):  
R. E. Taam
Keyword(s):  
Binary System ◽  
Time Scale ◽  
Binary Systems ◽  
Efficiency Factor ◽  
Final Phase ◽  
Common Envelope ◽  
Orbital Decay ◽  
Mass Outflow ◽  
The Common ◽  
Orbital Periods

AbstractThe current understanding of the common envelope binary phase of evolution is presented. The results obtained from the detailed computations of the hydrodynamical evolution of this phase demonstrate that the deposition of energy by the double core via frictional processes is sufficiently rapid to drive a mass outflow, primarily in the equatorial plane of the binary system. Specifically, recent calculations suggest that large amounts of mass and angular momentum can be lost from the binary system in a such a phase. Since the time scale for mass loss at the final phase of evolution is much shorter than the orbital decay time scale of the companion, the tranformation of binary systems from long orbital periods (> month) to short orbital periods (< day) is likely. The energy efficiency factor for the process is estimated to lie in the range between 0.3 and 0.6.

scholarly journals The Ejecta of Classical Novae

2001 ◽  
Vol 205 ◽  
pp. 260-263
Author(s):  
T.J. O'Brien ◽  
R.J. Davis ◽  
M.F. Bode ◽  
S. P. S. Eyres ◽  
J.M. Porter
Keyword(s):  
Coherent Structures ◽  
White Dwarf ◽  
Binary Stars ◽  
Hubble Space Telescope ◽  
Classical Novae ◽  
Common Envelope ◽  
Physical Mechanisms ◽  
The Common ◽  
Thermonuclear Runaway ◽  
Prolate Ellipsoidal

Classical novae are interacting binary stars in which a thermonuclear runaway in material accreted onto a white dwarf from a companion red dwarf results in the ejection of around 10−4M⊙ at hundreds to thousands of kilometres per second. Recent Hubble Space Telescope and MERLIN imaging of the expanding ejecta from several classical novae are presented. In general the ejecta are clumpy but often display coherent structures, most notably equatorial rings of enhanced emission encircling prolate ellipsoidal shells. Physical mechanisms (including the common envelope phase and anisotropic irradiation of the shell) which may result in the generation of these structures are discussed.

scholarly journals Critical Mass for Merging in Double White Dwarfs

1989 ◽  
Vol 114 ◽  
pp. 450-453
Author(s):  
Izumi Hachisu ◽  
Mariko Kato
Keyword(s):  
Mass Transfer ◽  
Gravitational Radiation ◽  
White Dwarf ◽  
Binary Stars ◽  
White Dwarfs ◽  
Radiation Effect ◽  
Critical Mass ◽  
Mass Transfer Rate ◽  
Roche Lobe ◽  
Common Envelope

We examine whether or not double white dwarfs are ultimately merging into one body. It has been argued that such a double white dwarf system forms from some intermediate-mass binary stars and will merge due to the gravitational radiation which decreases the separation of binary. After filling the inner critical Roche lobe, the less massive component begins to transfer its mass to the more massive one. When the mass transfer rate exceeds a some critical value, a common envelope is formed. If the common envelope is hydrostatic, the mass transfer is tuned up to be a some value which depends only on the white dwarf mass, radius, and the Roche lobe size. The mass transfer from the less massive to the more massive components leads the separation to increase. On the other hand, the gravitational radiation effect reduces the separation. Which effect wins determines the fate of double white dwarfs, that is, whether merging or not merging. Since the formula of the gravitational radiation effect is well known, we have studied the mass accretion rate in common envelope phase of double white dwarfs assuming the Roche lobe size is as small as 0.03 R⊙ or 0.1 R⊙.

scholarly journals Are white dwarf magnetic fields in close binaries generated during common-envelope evolution?

2019 ◽  
Vol 492 (1) ◽  
pp. 1523-1529 ◽  
Author(s):  
Diogo Belloni ◽  
Matthias R Schreiber
Keyword(s):  
Low Temperature ◽  
Magnetic Fields ◽  
Observational Data ◽  
White Dwarf ◽  
Close Binaries ◽  
Common Envelope ◽  
The Past ◽  
The Common ◽  
M Dwarf ◽  
Dynamo Process

ABSTRACT Understanding the origin of the magnetic fields in white dwarfs (WDs) has been a puzzle for decades. A scenario that has gained considerable attention in the past years assumes that such magnetic fields are generated through a dynamo process during common-envelope evolution. We performed binary population models using an up-to-date version of the bse code to confront the predictions of this model with observational results. We found that this hypothesis can explain only the observed distribution of WD magnetic fields in polars and pre-polars and the low-temperature WDs in pre-polars if it is re-scaled to fit the observational data. Furthermore, in its present version, the model fails to explain the absence of young, close detached WD+M-dwarf binaries harbouring hot magnetic WDs and predicts that the overwhelming majority of WDs in close binaries should be strongly magnetic, which is also in serious conflict with the observations. We conclude that either the common-envelope dynamo scenario needs to be substantially revised or a different mechanism is responsible for the generation of strong WD magnetic fields in close binaries.

scholarly journals Studying the Progenitors of Type Ia Supernovae via Lensing with the Kepler Survey

2011 ◽  
Vol 7 (S281) ◽  
pp. 34-35
Author(s):  
Rosanne Di Stefano
Keyword(s):  
Mass Transfer ◽  
White Dwarf ◽  
Type Ia Supernovae ◽  
Valuable Insight ◽  
Common Envelope ◽  
Type Ia ◽  
Pass Through ◽  
Ia Supernovae ◽  
Insight Into

AbstractEvery model for the progenitors of Type Ia supernovae (SNe Ia) requires that binaries pass through an epoch during which a white dwarf (WD) orbits a non-degenerate star. Depending on the mass of the WD, the radius of its companion, and the orbital separation, the WD may lens its companion. The lensing event would be an antitransit, an increase in light from the companion that can rise to the level of a percent or more, during an interval of hours. Antitransits are periodic. By studying them we can determine the properties of both the WD and its companion, as well as the characteristics of the orbit. Lensing events of this type are almost certain to be observed by the Kepler mission, while some can even be detected by ground-based surveys. Antitransits and transits will both provide valuable insight into the end states of common envelope evolution and of stable mass transfer, resolving issues that must be understood before we can fully unravel the progenitor puzzle.

scholarly journals A New Progenitor Model of Type Ia Supernovae

1989 ◽  
Vol 8 ◽  
pp. 175-176
Author(s):  
Izumi Hachisu ◽  
Mariko Kato ◽  
Hideyuki Saio
Keyword(s):  
Mass Transfer ◽  
White Dwarf ◽  
Transfer Rate ◽  
Mass Transfer Rate ◽  
Supernova Explosion ◽  
Core Mass ◽  
Common Envelope ◽  
Type Ia ◽  
Red Giant ◽  
Ia Supernovae

AbstractA new progenitor model of Type la supernovae (SNe Ia) is proposed. The model consists of a carbon-oxygen white dwarf (0.8-1.2 M⊙) and a low-mass red giant star (0.8-1.5 M⊙) with a helium core (0.2-0.4 M⊙). When a red giant fills its inner critical Roche lobe and its mass transfer rate exceeds a critical value, a common envelope state is realized. Then the mass accretion rate onto the white dwarf, i.e., the mass transfer rate is tuned up to be Ṁ= 8.5 × 10−7 (MWD/M⊙-0.52) M⊙ yr−1, where MWD is the mass of the white dwarf. This rate is high enough to suppress the hydrogen shell flashes, but too low for carbon to be ignited off-center. When the carbon-oxygen core mass grows to the Chandrasekhar limit during the common envelope phase, a Type la supernova explosion is expected to occur.

scholarly journals Hot subdwarf B stars with neutron star components

2020 ◽  
Vol 634 ◽  
pp. A126 ◽  
Author(s):  
You Wu ◽  
Xuefei Chen ◽  
Hailiang Chen ◽  
Zhenwei Li ◽  
Zhanwen Han
Keyword(s):  
Mass Transfer ◽  
Neutron Star ◽  
Main Sequence ◽  
Galactic Disk ◽  
B Stars ◽  
Common Envelope ◽  
Subdwarf B Stars ◽  
Linear Formula ◽  
The Galaxy ◽  
The Common

Context. Subdwarf B stars (sdBs) play a crucial role in stellar evolution, asteroseismology, and far-UV radiation of early-type galaxies, and have been intensively studied with observation and theory. It has theoretically been predicted that sdBs with neutron star (NS) companions exist in the Galaxy, but none have been discovered yet. This remains a puzzle in this field. In a previous study (hereafter Paper I), we have studied the formation channels of sdB+NS binaries from main-sequence (MS) stars plus NS binaries by establishing a model grid, but it is still unclear how these binaries consisting of MS stars and NS binaries came to be in the first place. Aims. We systematically study the formation of sdB+NS binaries from their original zero-age main-sequence progenitors. We bridge the gap left by our previous study in this way. We obtain the statistical population properties of sdB+NS binaries and provide some guidance for observational efforts. Methods. We first used Hurley’s rapid binary evolution code BSE to evolve 107 primordial binaries to the point where the companions of NS+MS, NS+Hertzsprung gap star, and NS+Giant Branch star binaries have just filled their Roche lobes. Next, we injected these binaries into the model grid we developed in Paper I to obtain the properties of the sdB+NS populations. We adopted two prescriptions of NS natal kicks: the classical Maxwellian distribution with a dispersion of σ = 265 km s−1, and a linear formula that assumes that the kick velocity is associated with the ratio of ejected to remnant mass. Different values of αCE, where αCE is the common-envelope ejection efficiency, were chosen to examine the effect of common-envelope evolution on the results. Results. In the Galaxy, the birthrate of sdB+NS binaries is about 10−4 yr−1 and there are ∼7000 − 21 000 such binaries. This contributes 0.3−0.5% of all sdB binaries in the most favorable case. Most Galactic sdB+NS binaries (≳60%) arise from the channel of stable mass transfer. The value of αCE has little effect on the results, but when we use the linear formula prescription of NS natal kick, the number and birthrate doubles in comparison to the results we obtained with the Maxwellian distribution. The orbital periods of sdB+NS binaries from different formation channels differ significantly, as expected. This results in two peaks in the radial velocity (RV) semi-amplitude distribution: 100 − 150 km s−1 for stable mass transfer, and 400 − 600 km s−1 for common-envelope ejection. However, the two sdB+NS binary populations exhibit similar delay-time distributions, which both peak at about 0.2 Gyr. This indicates that Galactic sdB+NS binaries are born in very young populations, probably in the Galactic disk. The sdB+NS binaries produced from the common-envelope ejection channel are potential sources of strong gravitational wave radiation (GWR), and about ∼100 − 300 could be detected by the Laser Interferometer Space Antenna (LISA) with a signal-to-noise ratio of 1. Conclusions. Most sdB+NS binaries are located in the Galactic disk with small RV semi-amplitudes. SdB+NS binaries with large RV semi-amplitudes are expected to be strong GWR sources, some of which could be detected by LISA in the future.

scholarly journals Evolutionary Scenarios for Double Degenerate Systems

1996 ◽  
Vol 158 ◽  
pp. 459-460
Author(s):  
P. B. Marks ◽  
M. J. Sarna ◽  
R. C. Smith
Keyword(s):  
Mass Transfer ◽  
Orbital Period ◽  
White Dwarf ◽  
Massive Star ◽  
Roche Lobe ◽  
Orbital Parameters ◽  
Common Envelope ◽  
Orbital Periods ◽  
Two Phases ◽  
The Masses

There are presently eight double degenerate systems with well determined orbital parameters, their periods being either a few hours or a few days (Marsh, Dhillon & Duck 1995; Marsh 1995). The masses of the primaries and secondaries lie in the range 0.15… 0.45M⊙.We calculate two evolutionary scenarios (Sarna, Marks & Smith 1996); the first is Algol-type evolution with two phases of stable mass transfer, and the second involves first a stage of common envelope (CE) evolution followed by a stage of stable mass transfer. In both calculations we assume non-conservative mass transfer by which we mean that the total mass and angular momentum of the system are not conserved. For both scenarios we start our calculations after the first stage of mass transfer has finished. In all calculations the primary is the initially more massive star that filled its Roche lobe and transferred material to the secondary during the first phase of mass transfer, hence the secondary is the star that fills its Roche lobe in our calculations. The system’s orbital period decreases and then increases until the system detaches; we are left with a detached white dwarf/white dwarf binary with an orbital period of the order of hours or of days (see Table 1). There must exist some bifurcation period below which the systems evolve towards orbital periods of the order of hours and above which the systems evolve to periods of the order of several days.

scholarly journals Energy and Angular Momentum Deposition During Common Envelope Evolution

2004 ◽  
Vol 194 ◽  
pp. 30-32
Author(s):  
Noam Soker
Keyword(s):  
Angular Momentum ◽  
Mass Loss ◽  
Orbital Angular Momentum ◽  
White Dwarf ◽  
Early Stage ◽  
Mass Loss Rate ◽  
Orbital Energy ◽  
Giant Star ◽  
Common Envelope ◽  
The Common

AbstractI consider three processes which enhance mass loss rate from a common envelope of a giant star with a main sequence or a white dwarf companion spiraling-in inside its envelope. I consider deposition of orbital energy and orbital angular momentum to the giant's envelope, and the formation of jets by an accreting companion and their propagation in the envelope. I find that in many cases the deposition of orbital angular momentum to the envelope may be more important to the mass loss process than the deposition of orbital energy. Jets blown by an accreting companion, in particular a white dwarf, orbiting inside the outer regions of the giant's envelope may also dominate over orbital energy deposition at early stage of the common envelope evolution. These imply that, studies which ignore the deposition of angular momentum to the envelope and the effects of the accreting companion may reach wrong conclusions.

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