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 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 ROSAT observations of non-magnetic CVs

1996 ◽  
Vol 158 ◽  
pp. 273-276 ◽  
Author(s):  
A. van Teeseling ◽  
F. Verbunt ◽  
K. Beuermann
Keyword(s):  
Boundary Layer ◽  
Accretion Disk ◽  
White Dwarf ◽  
Accretion Rate ◽  
Cataclysmic Variables ◽  
Rotation Velocity ◽  
X Rays ◽  
X Ray ◽  
Orbital Modulation ◽  
Magnetic Cataclysmic Variables

In non-magnetic cataclysmic variables the accreted matter forms an accretion disk around the white dwarf. In the boundary layer between the white dwarf and the accretion disk the accreted matter decelerates from Keplerian velocities to the rotation velocity of the white dwarf. If the accretion rate is high the boundary layer would be optically thick and cool (T ~ 105K), and if the accretion rate is low the boundary layer would be optically thin and hot (T ~ 108K) (Pringle & Savonije 1979).There are several observational problems with this simple picture: a soft X-ray component could only be detected so far in 5 dwarf novae in outburst and not in any nova-like variable. Also in high-accretion-rate systems there is a hot optically thin X-ray source, which has, however, an X-ray luminosity which is much less than the UV luminosity of the system (van Teeseling & Verbunt 1994). Finally, there is evidence for orbital modulation in the X-rays from some systems (e.g. van Teeseling et al. 1995).

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 Extreme Ultraviolet Spectroscopy of Magnetic Cataclysmic Variables

1996 ◽  
Vol 152 ◽  
pp. 309-316
Author(s):  
Frits Paerels ◽  
Min Young Hur ◽  
Christopher W. Mauche
Keyword(s):  
High Resolution ◽  
White Dwarf ◽  
Extreme Ultraviolet ◽  
Cataclysmic Variables ◽  
Ultraviolet Spectroscopy ◽  
Temperature Structure ◽  
Polar Cap ◽  
Ultraviolet Emission ◽  
X Ray ◽  
Magnetic Cataclysmic Variables

A longstanding problem in the interpretation of the X-ray and extreme ultraviolet emission from strongly magnetic cataclysmic variables can be addressed definitively with high resolution EUV spectroscopy. A detailed photospheric spectrum of the accretion-heated polar cap of the white dwarf is sensitive in principle to the temperature structure of the atmosphere. This may allow us to determine where and how the bulk of the accretion energy is thermalized. The EUVE data on AM Herculis and EF Eridani are presented and discussed in this context.

scholarly journals Soft X-Ray Spectroscopy with Exosat

1984 ◽  
Vol 86 ◽  
pp. 59-66
Author(s):  
R. Mewe
Keyword(s):  
Absorption Edge ◽  
White Dwarf ◽  
White Dwarfs ◽  
Cataclysmic Variables ◽  
Atmospheric Model ◽  
Abundance Ratio ◽  
The Other ◽  
X Ray ◽  
Element Abundances ◽  
Medium Resolution

With the 500 and 1000 l/mm transmission gratings aboard the European x-ray Observatory SATellite (EXOSAT) we have measured medium-resolution (Δλ 5 A at 100 A) spectra of some ten objects of various categories such as isolated white dwarfs, cool stars with convective mantles, cataclysmic variables (e.g. AM Her) and a high-luminosity X-ray source (Sco X-1).The Instrument configuration was mostly such that one low-energy telescope was used as a photometer, while the other telescope was used as a spectrometer with the 500 l/mm grating inserted.The white dwarf spectra were measured between about 60 and 300 A. They show a continuum with no clear evidence of aborption and emission lines except for the He II absorption edge at 227 A in the spectrum of Feige 24. For the cooler (28 000 K) white dwarf Sirius B the emission is peaked between about 100 and 160 A and limited to about 200 A. which can be expected from atmospheric model spectra of DA white dwarfs. The soft X-ray emission of the hotter (> 60 000 K) DA white dwarfs (HZ43. Feige 24) is also interpreted in terms of photospheric emission. In the HZ43 spectrum the absorption edge is apparently absent which sets a stringent upper limit to the abundance ratio He/H of about 10−5. On the other hand the spectrum of Feige 24 shows a dominant absorption edge, implying He/H > 10−3. Moreover, here the shape of the continuum may be indicative of a stratification of element abundances in the outer atmosphere.

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 Determining the masses of white dwarfs in magnetic cataclysmic variables from x-ray observations

1997 ◽  
Vol 189 ◽  
pp. 115-118
Author(s):  
Kinwah Wu ◽  
Mark Cropper ◽  
Gavin Ramsay
Keyword(s):  
White Dwarfs ◽  
Cataclysmic Variables ◽  
Orbital Inclination ◽  
X Ray ◽  
Magnetic Cataclysmic Variables ◽  
The Masses

A method to determine the masses of white dwarfs in magnetic cataclysmic variables from X-ray observations is presented. The method is appropriate for both eclipsing and non-eclipsing systems, for it is insensitive to the orbital inclination of the systems.

SPIN PERIODICITY MEASUREMENTS OF WHITE DWARFS HOSTED IN SOUTHERN HARD X–RAY INTERMEDIATE POLAR CANDIDATES

2010 ◽  
Vol 19 (06) ◽  
pp. 797-803
Author(s):  
ILEANA ANDRUCHOW ◽  
NICOLA MASETTI ◽  
DOMITILLA DE MARTINO ◽  
SERGIO A. CELLONE ◽  
ELENA MASON ◽  
...  
Keyword(s):  
Optical Spectroscopy ◽  
White Dwarf ◽  
Preliminary Analysis ◽  
Cataclysmic Variables ◽  
Optical Spectra ◽  
X Rays ◽  
Optical Photometry ◽  
X Ray ◽  
Orbital Periods ◽  
Magnetic Cataclysmic Variables

Thanks to the combination of hard X–ray data afforded with the INTEGRAL satellite and optical spectroscopy at various telescopes, a number of new, possibly magnetic, Cataclysmic Variables (CVs) has been recently discovered. We here report on the preliminary analysis of B-band optical photometry performed with the 2.15m "Jorge Sahade" telescope at CASLEO (Argentina) on 5 CVs discovered at hard X–rays with INTEGRAL and which show features of a magnetic white dwarf (WD) in their optical spectra. The aim of these observations is to derive the orbital periods of these systems and the spin periodicity of their accreting WD.

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