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 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 The White Dwarf Binary Pathways Survey – IV. Three close white dwarf binaries with G-type secondary stars

2020 ◽  
Vol 501 (2) ◽  
pp. 1677-1689
Author(s):  
M S Hernandez ◽  
M R Schreiber ◽  
S G Parsons ◽  
B T Gänsicke ◽  
F Lagos ◽  
...  
Keyword(s):  
Spectral Type ◽  
White Dwarf ◽  
Binary Stars ◽  
Cataclysmic Variable ◽  
Common Envelope ◽  
History Of ◽  
Low Mass ◽  
Orbital Periods ◽  
M Dwarf

ABSTRACT Constraints from surveys of post-common envelope binaries (PCEBs) consisting of a white dwarf plus an M-dwarf companion have led to significant progress in our understanding of the formation of close white dwarf binary stars with low-mass companions. The white dwarf binary pathways project aims at extending these previous surveys to larger secondary masses, i.e. secondary stars of spectral-type AFGK. Here, we present the discovery and observational characterization of three PCEBs with G-type secondary stars and orbital periods between 1.2 and 2.5 d. Using our own tools as well as MESA, we estimate the evolutionary history of the binary stars and predict their future. We find a large range of possible evolutionary histories for all three systems and identify no indications for differences in common envelope evolution compared to PCEBs with lower mass secondary stars. Despite their similarities in orbital period and secondary spectral type, we estimate that the future of the three systems is very different: TYC 4962-1205-1 is a progenitor of a cataclysmic variable system with an evolved donor star, TYC 4700-815-1 will run into dynamically unstable mass transfer that will cause the two stars to merge, and TYC 1380-957-1 may appear as supersoft source before becoming a rather typical cataclysmic variable star.

scholarly journals Leon Mestel. 5 August 1927 — 15 September 2017

2021 ◽  
Vol 70 ◽  
pp. 335-358
Author(s):  
Robert Connon Smith ◽  
Nigel Weiss
Keyword(s):  
Magnetic Fields ◽  
Observational Data ◽  
Galaxy Formation ◽  
White Dwarf ◽  
Royal Society ◽  
Theoretical Models ◽  
Great Demand ◽  
Wide Range

Leon Mestel was best known for his wide-ranging work on cosmic magnetism, but he also worked on an equally wide range of non-magnetic problems in astrophysics, from star and galaxy formation to white dwarf cooling. Despite his work being primarily theoretical and highly mathematical, he was always aware of all the relevant observational data that both needed to be explained and also provided constraints for his theoretical models. He was internationally recognized as an authority on the influence of magnetic fields in astronomy, receiving a number of significant honours. He also had a deserved reputation for scrupulous honesty and integrity in his work. His life's work culminated in the publication of two editions of a magisterial monograph on stellar magnetism. He collaborated widely, influenced many other researchers and was in great demand as a conference speaker. He was also a conscientious academic, taking his full part in departmental teaching and administration, and a delightful companion and friend to all who knew him. He was well known for his many stories and jokes, which were widely enjoyed. His outside interests included being a long-standing member of the Editorial Board of this publication, Biographical Memoirs of Fellows of the Royal Society .

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.

scholarly journals Inferred time-scales for common envelope ejection using wide astrometric companions

2020 ◽  
Vol 494 (1) ◽  
pp. 1448-1462 ◽  
Author(s):  
Andrei P Igoshev ◽  
Hagai B Perets ◽  
Erez Michaely
Keyword(s):  
Mass Loss ◽  
Time Scales ◽  
Cataclysmic Variables ◽  
Close Binaries ◽  
Ejection Time ◽  
Common Envelope ◽  
Use Of Data ◽  
The Common ◽  
F Stars ◽  
Gaia Dr2

ABSTRACT Evolution of close binaries often proceeds through the common envelope stage. The physics of the envelope ejection (CEE) is not yet understood, and several mechanisms were suggested to be involved. These could give rise to different time-scales for the CEE mass-loss. In order to probe the CEE-time-scales we study wide companions to post-CE binaries. Faster mass-loss time-scales give rise to higher disruption rates of wide binaries and result in larger average separations. We make use of data from Gaia DR2 to search for ultrawide companions (projected separations 103–2 × 105 au and M2 > 0.4 M⊙) to several types of post-CEE systems, including sdBs, white dwarf post-common binaries, and cataclysmic variables. We find a (wide-orbit) multiplicity fraction of 1.4 ± 0.2 per cent for sdBs to be compared with a multiplicity fraction of 5.0 ± 0.2 per cent for late-B/A/F stars which are possible sdB progenitors. The distribution of projected separations of ultrawide pairs to main sequence stars and sdBs differs significantly and is compatible with prompt mass-loss (upper limit on common envelope ejection time-scales of 102 yr). The smaller statistics of ultrawide companions to cataclysmic variables and post-CEE binaries provide weaker constraints. Nevertheless, the survival rate of ultrawide pairs to the cataclysmic variables suggest much longer, ∼104 yr time-scales for the CEE in these systems, possibly suggesting non-dynamical CEE in this regime.

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 Testing Common Envelope Theories with White Dwarf Binaries

2004 ◽  
Vol 194 ◽  
pp. 39-40
Author(s):  
G. Nelemans ◽  
C.A. Tout
Keyword(s):  
Mass Transfer ◽  
Angular Momentum ◽  
Stellar Evolution ◽  
White Dwarf ◽  
White Dwarfs ◽  
Momentum Balance ◽  
Close Binaries ◽  
Transfer Phase ◽  
Common Envelope ◽  
Binary Evolution

AbstractWe determine the possible masses and radii of the progenitors of white dwarfs in binaries from fits to detailed stellar evolution models and use these to reconstruct the mass-transfer phase in which the white dwarf was formed. We confirm the earlier finding that in the first phase of mass transfer in the binary evolution leading to a close pair of white dwarfs, the standard common-envelope formalism based on energy balance in the system, does not work. A formalism based on angular momentum balance can explain the observations. We extend our analysis to all close binaries with at least one white dwarf component. Comparing the two, we show that the formalism based on angular momentum balance can explain all observations at least as well as the energy formalism.

scholarly journals Common Envelope Evolution of Binary Stars

1989 ◽  
Vol 107 ◽  
pp. 299-310
Author(s):  
Mario Livio
Keyword(s):  
White Dwarf ◽  
Binary Stars ◽  
Energy Deposition ◽  
Binary Systems ◽  
Planetary Nebulae ◽  
Close Binary ◽  
Type I ◽  
Common Envelope ◽  
The Common

AbstractWe discuss the common envelope phase in the evolution of binary systems. The problem of the efficiency of energy deposition into envelope ejection is treated in some detail. We describe the implications of common envelope evolution for the shaping of planetary nebulae with close binary nuclei and for double white dwarf systems, considered to be the progenitors of Type I supernovae.

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