scholarly journals Magnetic white dwarfs in post-common-envelope binaries

2021 ◽  
Vol 502 (3) ◽  
pp. 4305-4327
Author(s):  
S G Parsons ◽  
B T Gänsicke ◽  
M R Schreiber ◽  
T R Marsh ◽  
R P Ashley ◽  
...  
Keyword(s):  
White Dwarf ◽  
White Dwarfs ◽  
Cataclysmic Variables ◽  
Light Curves ◽  
Magnetic Systems ◽  
Cataclysmic Binaries ◽  
Low Mass ◽  
Detached Binaries ◽  
Magnetic Cataclysmic Variables ◽  
First Time

ABSTRACT Magnitude-limited samples have shown that 20–25 per cent of cataclysmic variables contain white dwarfs with magnetic fields of Mega Gauss strength, in stark contrast to the approximately 5 per cent of single white dwarfs with similar magnetic field strengths. Moreover, the lack of identifiable progenitor systems for magnetic cataclysmic variables leads to considerable challenges when trying to understand how these systems form and evolve. Here, we present a sample of six magnetic white dwarfs in detached binaries with low-mass stellar companions where we have constrained the stellar and binary parameters including, for the first time, reliable mass estimates for these magnetic white dwarfs. We find that they are systematically more massive than non-magnetic white dwarfs in detached binaries. These magnetic white dwarfs generally have cooling ages of more than 1 Gyr and reside in systems that are very close to Roche lobe filling. Our findings are more consistent with these systems being temporarily detached cataclysmic variables, rather than pre-cataclysmic binaries, but we cannot rule out the latter possibility. We find that these systems can display unusual asymmetric light curves that may offer a way to identify them in larger numbers in future. Seven new candidate magnetic white dwarf systems are also presented, three of which have asymmetric light curves. Finally, we note that several newly identified magnetic systems have archival spectra where there is no clear evidence of magnetism, meaning that these binaries have been previously missed. Nevertheless, there remains a clear lack of younger detached magnetic white dwarf systems.

scholarly journals Radiation-hydrodynamic Models of the Accretion Spots in Magnetic Cataclysmic Variables

2004 ◽  
Vol 190 ◽  
pp. 187-200 ◽  
Author(s):  
K. Beuermann
Keyword(s):  
Mass Flux ◽  
White Dwarf ◽  
Cataclysmic Variables ◽  
Strong Shock ◽  
Hydrodynamic Models ◽  
Mass Fluxes ◽  
Open Questions ◽  
Low Mass ◽  
Magnetic Cataclysmic Variables ◽  
Theoretical Foundations

AbstractThe structure of the near-polar accretion spots on accreting magnetic white dwarfs has been studied theoretically and observationally in numerous papers over the last decade. Detailed treatments are available for the regime of low mass flux, usually termed the bombardment case, and for higher mass fluxes which create a strong shock standing above the photosphere of the white dwarf. No general treatment is so far available for the case of shocks buried deep in the photosphere. I review the theoretical foundations, present some applications of theory, and discuss in short the open questions which still need to be addressed.

scholarly journals Blobby Accretion in Magnetic Cataclysmic Variables

2004 ◽  
Vol 190 ◽  
pp. 265-271
Author(s):  
A. V. Halevin ◽  
I. L. Andronov ◽  
N. M. Shakhovskoy ◽  
S. V. Kolesnikov ◽  
N. I. Ostrova
Keyword(s):  
Drag Force ◽  
Shot Noise ◽  
White Dwarf ◽  
White Dwarfs ◽  
Cataclysmic Variables ◽  
Active Regions ◽  
Force Model ◽  
Smooth Particle Hydrodynamics ◽  
Particle Hydrodynamics ◽  
Magnetic Cataclysmic Variables

AbstractThe processes of accretion of the gaseous blobs with different masses and densities onto strongly magnetized white dwarfs in the systems of polars have been modelled. We prove that shot noise in blue wavelengths represents accretion of the smaller and denser blobs than in redder wavelengths. Using combined “smooth particle hydrodynamics - drag force” model, we have predicted a shape of the accretion stream and active regions on the white dwarf surface.

scholarly journals Mass Measurement of Accreting Magnetic White Dwarfs with Hard X-Ray Spectroscopy

1998 ◽  
Vol 188 ◽  
pp. 97-100
Author(s):  
M. Ishida ◽  
R. Fujimoto
Keyword(s):  
White Dwarf ◽  
White Dwarfs ◽  
Mass Measurement ◽  
Cataclysmic Variables ◽  
Magnetic Pole ◽  
X Ray ◽  
Secondary Star ◽  
Magnetic Cataclysmic Variables ◽  
Image Position ◽  
The Magnetic Field

Accreting magnetic white dwarfs are usually found as component stars in Magnetic Cataclysmic Variables (MCVs), in which a white dwarf with B = 105-8 G accepts mass from a late type (secondary) star via Roche Lobe overflow. Matter from the secondary is funneled by the magnetic field and concentrates on the magnetic pole(s) of the white dwarf. Since the accretion flow becomes highly supersonic, a standing shock wave is formed close to the white dwarf. The temperature of the plasma at the shock front reflects the gravitational potential and can be denoted as a function of the mass (M) and the radius (R) of the white dwarf as: Note here that the height of the shock is expected to be within 10% of the white dwarf radius, and hence neglected here.

scholarly journals White Dwarfs in Cataclysmic Variables: An Update

2015 ◽  
Vol 2 (1) ◽  
pp. 35-40
Author(s):  
E. M. Sion ◽  
P. Godon
Keyword(s):  
White Dwarf ◽  
White Dwarfs ◽  
Cataclysmic Variables ◽  
Chemical Abundances ◽  
Rotation Rates ◽  
Surface Temperatures ◽  
Accretion Rates ◽  
Magnetic Cataclysmic Variables ◽  
Far Ultraviolet ◽  
Nova Outburst

In this review, we summarize what is currently known about the surface temperatures of accreting white dwarfs in nonmagnetic and magnetic cataclysmic variables (CVs) based upon synthetic spectral analyses of far ultraviolet data. We focus only on white dwarf surface temperatures, since in the area of chemical abundances, rotation rates, WD masses and accretion rates, relatively little has changed since our last review, pending the results of a large HST GO program<br />involving 48 CVs of different CV types. The surface temperature of the white dwarf in SS Cygni is re-examined in the light of its revised distance. We also discuss new HST spectra of the recurrent nova T Pyxidis as it transitioned into quiescence following its April 2011 nova outburst.

scholarly journals Hydrogen Depletion and the Evolution of Cataclysmic Variables to Low Mass X-Ray Binaries

1987 ◽  
Vol 93 ◽  
pp. 681-685
Author(s):  
R.E. Williams ◽  
M.M. Phillips ◽  
S.R. Heathcote
Keyword(s):  
Emission Line ◽  
White Dwarf ◽  
White Dwarfs ◽  
Cataclysmic Variables ◽  
Core Collapse ◽  
X Ray ◽  
Low Mass ◽  
Recurrent Nova ◽  
Chandrasekhar Limit ◽  
X Ray Binaries

AbstractCertain cataclysmic variables may evolve into low mass X-ray binaries if the white dwarfs can steadily accrete sufficient mass to exceed the Chandrasekhar limit. We present spectra of a recurrent nova and a low mass X-ray binary which are very similar to each other, and are also unusual for the strengths of the observed He II emission. We suggest that this similarity is not coincidental, but is evidence for an evolutionary link between the two classes of objects. A hydrogen depletion in the accreting gas is implied from the emission line fluxes, and may be an important parameter in determining whether accreted gas remains bound to the white dwarf, enabling eventual core collapse to occur.

scholarly journals Measuring the masses of magnetic white dwarfs: a NuSTAR legacy survey

2020 ◽  
Vol 498 (3) ◽  
pp. 3457-3469
Author(s):  
A W Shaw ◽  
C O Heinke ◽  
K Mukai ◽  
J A Tomsick ◽  
V Doroshenko ◽  
...  
Keyword(s):  
Angular Momentum ◽  
White Dwarf ◽  
White Dwarfs ◽  
Cataclysmic Variables ◽  
Weighted Average ◽  
Velocity Measurements ◽  
X Ray ◽  
Common Envelope ◽  
Magnetic Cataclysmic Variables ◽  
The Masses

ABSTRACT The hard X-ray spectrum of magnetic cataclysmic variables can be modelled to provide a measurement of white dwarf mass. This method is complementary to radial velocity measurements, which depend on the (typically rather uncertain) binary inclination. Here, we present results from a Legacy Survey of 19 magnetic cataclysmic variables with NuSTAR. We fit accretion column models to their 20–78 keV spectra and derive the white dwarf masses, finding a weighted average $\bar{M}_{\rm WD}=0.77\pm 0.02$ M⊙, with a standard deviation σ = 0.10 M⊙, when we include the masses derived from previous NuSTAR observations of seven additional magnetic cataclysmic variables. We find that the mass distribution of accreting magnetic white dwarfs is consistent with that of white dwarfs in non-magnetic cataclysmic variables. Both peak at a higher mass than the distributions of isolated white dwarfs and post-common-envelope binaries. We speculate as to why this might be the case, proposing that consequential angular momentum losses may play a role in accreting magnetic white dwarfs and/or that our knowledge of how the white dwarf mass changes over accretion–nova cycles may also be incomplete.

scholarly journals Hard X-ray Observations of Magnetic Cataclysmic Variables

2004 ◽  
Vol 190 ◽  
pp. 135-141 ◽  
Author(s):  
K. P. Singh ◽  
V. R. Rana ◽  
K. Mukerjee ◽  
P. Barrett ◽  
E. M. Schlegel
Keyword(s):  
Cataclysmic Variables ◽  
Type Systems ◽  
Light Curves ◽  
Average Intensity ◽  
Spectral Parameters ◽  
X Ray ◽  
Orbital Modulation ◽  
Magnetic Cataclysmic Variables ◽  
The Masses ◽  
First Time

AbstractHard X-ray light curves and spectral parameters from our analysis of X-ray data of five AM Her type systems – V2301 Oph, V1432 Aql, EP Draconis, GG Leonis, & V834 Cen, and one intermediate polar – TV Col, observed using the Rossi X — ray Timing Explorer (RXTE) satellite are presented. A new improved ephemeris has been derived for V2301 Oph using the mid-eclipse timings. Average intensity variations, without any change of shape of the light curve or hardness ratio, are observed on timescales of a few days to a few months in V2301 Oph. V1432 Aql shows erratic variations on a timescale of a day, at least two sharp dips near orbital phases 0.35 and 0.5, and a total eclipse. Hard X-ray eclipses are also reported in EP Dra and GG Leo. V834 Cen shows intensity variations on yearly timescale and is found to be in a low state in 2002. In TV Col, a binary orbital modulation at 5.5h, in addition to the spin period of 1910s, is reported for the first time. Maximum spectral temperatures in Polars have been determined and used to estimate the masses of the white dwarfs.

scholarly journals Simulating AXAF Grating Spectra of Accreting White Dwarfs

1998 ◽  
Vol 15 (3) ◽  
pp. 339-347 ◽  
Author(s):  
Allyn F. Tennant ◽  
Kinwah Wu ◽  
Stephen L. O'Dell ◽  
Martin C. Weisskopf
Keyword(s):  
White Dwarf ◽  
White Dwarfs ◽  
Accretion Rate ◽  
Cataclysmic Variables ◽  
High Energy ◽  
High Spectral Resolution ◽  
X Ray ◽  
Transmission Grating ◽  
Magnetic Cataclysmic Variables ◽  
Very High

AbstractWe present simulated AXAF spectra of accreting white dwarfs, using parameters appropriate for magnetic cataclysmic variables. The very high spectral resolution that can be obtained with the High-Energy Transmission Grating of AXAF can resolve the keV X-ray emission lines that characterise the temperature, density and velocity profiles of the shock-heated emission regions of these systems. These simulations demonstrate that actual spectra will allow us to place constraints on the white-dwarf mass and the accretion rate of the systems. The high-resolution spectra also allow the measurement of the velocity of the accretion flow in regions close to the white-dwarf surface.

scholarly journals Direct detection of atomic dark matter in white dwarfs

2021 ◽  
Vol 2021 (3) ◽  
Author(s):  
David Curtin ◽  
Jack Setford
Keyword(s):  
Dark Matter ◽  
Energy Loss ◽  
Cooling Rate ◽  
White Dwarf ◽  
White Dwarfs ◽  
Luminosity Function ◽  
Direct Detection ◽  
Matter Density ◽  
Mixing Parameter ◽  
First Time

Abstract Dark matter could have a dissipative asymmetric subcomponent in the form of atomic dark matter (aDM). This arises in many scenarios of dark complexity, and is a prediction of neutral naturalness, such as the Mirror Twin Higgs model. We show for the first time how White Dwarf cooling provides strong bounds on aDM. In the presence of a small kinetic mixing between the dark and SM photon, stars are expected to accumulate atomic dark matter in their cores, which then radiates away energy in the form of dark photons. In the case of white dwarfs, this energy loss can have a detectable impact on their cooling rate. We use measurements of the white dwarf luminosity function to tightly constrain the kinetic mixing parameter between the dark and visible photons, for DM masses in the range 10−5–105 GeV, down to values of ϵ ∼ 10−12. Using this method we can constrain scenarios in which aDM constitutes fractions as small as 10−3 of the total dark matter density. Our methods are highly complementary to other methods of probing aDM, especially in scenarios where the aDM is arranged in a dark disk, which can make direct detection extremely difficult but actually slightly enhances our cooling constraints.

scholarly journals White Dwarf Stars

2017 ◽  
Vol 45 ◽  
pp. 1760023
Author(s):  
S. O. Kepler ◽  
Alejandra Daniela Romero ◽  
Ingrid Pelisoli ◽  
Gustavo Ourique
Keyword(s):  
White Dwarf ◽  
Final Stage ◽  
White Dwarfs ◽  
Sloan Digital Sky Survey ◽  
Dwarf Stars ◽  
Multiple Systems ◽  
White Dwarf Stars ◽  
Sky Survey ◽  
Data Release ◽  
Low Mass

White dwarf stars are the final stage of most stars, born single or in multiple systems. We discuss the identification, magnetic fields, and mass distribution for white dwarfs detected from spectra obtained by the Sloan Digital Sky Survey up to Data Release 13 in 2016, which lead to the increase in the number of spectroscopically identified white dwarf stars from 5[Formula: see text]000 to 39[Formula: see text]000. This number includes only white dwarf stars with [Formula: see text], i.e., excluding the Extremely Low Mass white dwarfs, which are necessarily the byproduct of stellar interaction.

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