scholarly journals The White Dwarf Binary Pathways Survey. V. The Gaia White Dwarf Plus AFGK Binary Sample and the Identification of 23 Close Binaries

2020 ◽  
Vol 905 (1) ◽  
pp. 38
Author(s):  
J.-J. Ren ◽  
R. Raddi ◽  
A. Rebassa-Mansergas ◽  
M. S. Hernandez ◽  
S. G. Parsons ◽  
...  
Keyword(s):  
White Dwarf ◽  
Close Binaries ◽  
Binary Sample

scholarly journals AM Herculis Binaries

1996 ◽  
Vol 165 ◽  
pp. 403-414 ◽  
Author(s):  
K. Beuermann
Keyword(s):  
White Dwarf ◽  
White Dwarfs ◽  
Close Binaries ◽  
Physical Processes ◽  
X Ray ◽  
Sky Survey

AM Herculis binaries contain mass accreting magnetic white dwarfs which appear as bright X-ray sources in the ROSAT All Sky Survey. About 52 systems are presently known which allow detailed studies of the evolution of magnetic close binaries and of fundamental plasma-physical processes in the accretion region on the white dwarf.

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 Evolution of Rotating White Dwarfs in Close Binaries and Diversity of Type Ia Supernovae

2003 ◽  
Vol 208 ◽  
pp. 459-460
Author(s):  
Tatsuhiro Uenishi ◽  
Ken'ichi Nomoto ◽  
Izumi Hachisu
Keyword(s):  
Angular Momentum ◽  
Accretion Disk ◽  
White Dwarf ◽  
Binary Systems ◽  
Close Binary ◽  
Close Binaries ◽  
Type Ia Supernovae ◽  
Rapid Rotation ◽  
Type Ia ◽  
Ia Supernovae

Type Ia supernovae are very good, but not perfect, standard candles, because their observed brightness shows a little diversity. The origin of this dibersity needs to be understood for the application to cosmology.In close binary systems, a white dwarf must be rotating faster and faster as it gains angular momentum from the accretion disk. Its rapid rotation affects its final mass and strucure just before a supernova expolosion. Brightness of supernovae can be changed if mass of their progenitors have some diversity.

scholarly journals Detection of White Dwarf companions to Blue Straggler Stars from UVIT observations of M67

2019 ◽  
Vol 14 (S351) ◽  
pp. 482-485
Author(s):  
Sindhu N ◽  
Annapurni Subramaniam ◽  
Aaron M. Geller ◽  
Vikrant Jadhav ◽  
Christian Knigge ◽  
...  
Keyword(s):  
White Dwarf ◽  
Binary Systems ◽  
Open Cluster ◽  
Ultra Violet ◽  
Close Binaries ◽  
Spectral Energy ◽  
Energy Distributions ◽  
Blue Straggler ◽  
Imaging Telescope ◽  
Stellar Mergers

AbstractWe investigate the old open cluster M67 using ultraviolet photometric data of Ultra-Violet Imaging Telescope in multi-filter far-UV bands. M67, well known for the presence of several blue straggler stars (BSS), has been put to detailed tests to understand their formation pathways. Currently, there are three accepted formation channels: mass transfer due to Roche-lobe overflow in binary systems, stellar mergers either due to dynamical collisions or through coalescence of close binaries. So far, there had not been any confirmed detection of a white dwarf (WD) companion to any of the BSSs in this cluster. Here, we present the detection of WD companions to 5 bright BSSs in M67. The multiwavelength spectral energy distributions covering 0.12 -11.5 μm range, were found to require binary spectral fits for 5 BSSs, consisting of a cool (BSS) and a hot companion. The parameters (Luminosity, Temperature, Radius and Mass) of the hot companions suggest them to be WDs with mass in the range 0.2 - 0.35 M⊙ with Teff ~11000 –24000 K.

scholarly journals Six detached white-dwarf close binaries

2005 ◽  
Vol 359 (2) ◽  
pp. 648-662 ◽  
Author(s):  
L. Morales-Rueda ◽  
T. R. Marsh ◽  
P. F. L. Maxted ◽  
G. Nelemans ◽  
C. Karl ◽  
...  
Keyword(s):  
White Dwarf ◽  
Close Binaries

scholarly journals Accretion Disk Instabilities

1986 ◽  
Vol 89 ◽  
pp. 249-267
Author(s):  
F. Meyer
Keyword(s):  
Light Curve ◽  
Accretion Disk ◽  
Accretion Disks ◽  
White Dwarf ◽  
Cataclysmic Variables ◽  
Outer Region ◽  
Stationary Flow ◽  
Close Binaries ◽  
Dwarf Novae ◽  
Low Mass

In this article we discuss two instabilities of stationary accretion disks which lead to an understanding of observed light variations in accretion disk systems, the dwarf novae and the rapid burster MXB 17030-335. The accretion disks in these systems avoid instability at the cost of stationarity and perform stable cycles in which sudden changes of the accretion flow lead to corresponding, often dramatic, variations of their accretion luminosity.Figure 1 shows a light curve of U Geminorum. It was discovered In 1855 by J.R. Hind and has become a prototype of the dwarf novae. In these systems an extended time of quiescence of up to several weeks Is followed by a short outburst of a few days during which the luminosity rises by a factor of 30 to 100. The dwarf novae belong to the cataclysmic variables. They are all close binaries In which a white dwarf primary is orbited by a Roche lobe-filling low mass secondary. Through the inner Lagrangian point mass flows over from the secondary and forms a luminious accretion disk around the white dwarf. In the case of the dwarf novae this disk has temperatures below about 10000K in Its outer region. It will be discussed how partial lonizatlon and convection then affect the vertical structure of the disk such that the stationary flow becomes unstable.Fig. 1. Light curve of the dwarf nova U Geminorum. Abszissa in days С [2])

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