scholarly journals Energy Distribution of Hard X-Ray Emitting Cataclysmic Variables

1983 ◽  
Vol 72 ◽  
pp. 173-180 ◽  
Author(s):  
Martine Mouchet
Keyword(s):  
Energy Distribution ◽  
Cataclysmic Variables ◽  
X Ray ◽  
Disc Model ◽  
Accretion Rates ◽  
Extreme Uv ◽  
Optical Continuum ◽  
Intermediate Polars ◽  
Standard Disc

ABSTRACTWe present the energy distribution of three hard X-ray sources H2252-035, 4U1849-31 and 2A0526-328 identified with intermediate polars. The ultraviolet and optical continuum can be well described by the standard disc model but this requires rather large discs and high accretion rates. Other possible contributions to the energy distribution are estimated. The predicted high accretion rates as well as the amplitude of the optical pulsations are in disagreement with the observed X-ray luminosity suggesting the existence of an unseen soft X-ray or extreme UV component.

scholarly journals White Dwarf Masses and Accretion Rates of Recurrent Novae: an X-ray Perspective

2011 ◽  
Vol 7 (S281) ◽  
pp. 186-189
Author(s):  
Koji Mukai ◽  
Jennifer L. Sokoloski ◽  
Thomas Nelson ◽  
Gerardo J. M. Luna
Keyword(s):  
White Dwarf ◽  
Cataclysmic Variables ◽  
The Other ◽  
X Ray ◽  
Other Hand ◽  
Accretion Rates

AbstractWe present recent results of quiescent X-ray observations of recurrent novae (RNe) and related objects. Several RNe are luminous hard X-ray sources in quiescence, consistent with accretion onto a near Chandrasekhar mass white dwarf. Detection of similar hard X-ray emissions in old novae and other cataclysmic variables may lead to identification of additional RNe candidates. On the other hand, other RNe are found to be comparatively hard X-ray faint. We present several scenarios that may explain this dichotomy, which should be explored further.

scholarly journals A Fuse Survey of Disk-Accreting Cataclysmic Variables

2004 ◽  
Vol 194 ◽  
pp. 251-251
Author(s):  
C. S. Froning ◽  
K. S. Long ◽  
P. Szkody ◽  
B. T. Gänsicke
Keyword(s):  
Cataclysmic Variables ◽  
Dwarf Novae ◽  
X Ray ◽  
Intermediate Polars ◽  
Far Ultraviolet ◽  
X Ray Binaries ◽  
Initial Results

We present initial results of a survey of the FUV spectra of disk-accreting cataclysmic variables obtained with the Far Ultraviolet Spectroscopic Explorer (FUSE).FUSE covers the 905 - 1188 Å range at spectral resolutions ≃0.1 Å. To date, FUSE has observed more than 65 cataclysmic variables (CVs). Publicly-available data include observations of 11 dwarf novae (DN), 15 non-magnetic novalikes (NLs), 7 intermediate polars and DQ Her stars, at least 15 polars, and 4 super-soft X-ray binaries.

scholarly journals X-Ray Observations of Cataclysmic Variables

1987 ◽  
Vol 93 ◽  
pp. 207-223
Author(s):  
J.P. Osborne
Keyword(s):  
Light Curve ◽  
Spectral Range ◽  
Cataclysmic Variables ◽  
High Sensitivity ◽  
Light Curves ◽  
X Ray ◽  
Broad Spectral Range ◽  
Intermediate Polars ◽  
Recurrent Nova

AbstractThe X-ray observatory EXOSAT spent over 1000 hours observing cataclysmic variables. Some of the major results reviewed here are: soft X-ray light curve changes in AM Her objects, orbital effects in the X-ray light curves of intermediate polars and U Gem, regular behaviour in the inter-outburst X-ray flux of VW Hyi, and X-ray emission from the tenuous remnant of the recent recurrent nova RS Oph. The ability of EXOSAT to make long uninterupted observations at high sensitivity over a broad spectral range and to react quickly to cosmic events has yielded a dataset of a quality that will not be surpassed for many years.

scholarly journals Mass Accretion in Intermediate Polar V1223 Sgr

2012 ◽  
Vol 8 (S290) ◽  
pp. 225-226
Author(s):  
Ladislav Hric ◽  
Emil Kundra ◽  
Rudolf Gális
Keyword(s):  
Accretion Rate ◽  
Spectral Band ◽  
Cataclysmic Variables ◽  
X Ray ◽  
Mass Accretion Rate ◽  
Intermediate Polars ◽  
Activity State

AbstractIntermediate polars (IPs) represent more than 70% of all cataclysmic variables (CVs) detected by INTEGRAL in hard X-ray. Nevertheless, only a quarter of all known IPs have been detected in this spectral band. This fact can be related to the activity state of these object ruled by changes in the mass accretion rate.

scholarly journals GLORIA and Study of Cataclysmic Variables

2015 ◽  
Vol 2 (1) ◽  
pp. 303-307
Author(s):  
R. Hudec ◽  
V. Šimon
Keyword(s):  
Open Access ◽  
Access Network ◽  
Cataclysmic Variables ◽  
X Ray ◽  
The World ◽  
Robotic Telescopes ◽  
Intermediate Polars

We report here on the ongoing EU FP7 Project GLORIA (GLObal Robotic-telescopes Intelligent Array) with emphasis on possibility of investigation of cataclysmic variables by users. GLORIA will enable the first free and open-access network of robotic telescopes in the world. We show several examples of the not often used topics (but suitable for GLORIA) for the studies of activity of cataclysmic variables, e.g. search for outbursts in intermediate polars and the fluctuations of brightness in their quiescence, and investigation of the optical counterparts of supersoft X-ray sources.

The Continuum Energy Distribution of the Old-Nova GK Per (1901)

1983 ◽  
Vol 72 ◽  
pp. 127-131
Author(s):  
A. Bianchini ◽  
F. Sabbadin
Keyword(s):  
Magnetic Field ◽  
Energy Distribution ◽  
White Dwarf ◽  
Late Type ◽  
X Ray ◽  
Physical Mechanisms ◽  
Continuum Energy ◽  
Field Lines ◽  
The Continuum ◽  
Standard Disc

ABSTRACTThe observed X-ray to IR continuum energy distribution of the old-nova GK Per, corrected for the contribution of the late-type secondary and for i.s. extinction,is found to be consistent with the model of an accreting magnetic white dwarf. Furthermore, we discuss plausible modifications of the standard disc structure caused by the presence of magnetic field lines threading the disc and evaluate the contribution to the observed radiation field from several physical mechanisms.

scholarly journals New transient Galactic bulge intermediate polar candidate XMMU J175035.2-293557

2018 ◽  
Vol 615 ◽  
pp. L7 ◽  
Author(s):  
F. Hofmann ◽  
G. Ponti ◽  
F. Haberl ◽  
M. Clavel
Keyword(s):  
Galactic Center ◽  
Cataclysmic Variables ◽  
Galactic Bulge ◽  
Optical Counterpart ◽  
X Ray ◽  
The Past ◽  
System A ◽  
Variable Factor ◽  
Intermediate Polars ◽  
X Ray Absorption

Context. For the past decades, a rare subclass of cataclysmic variables (CV), with magnetised white dwarfs (WD) as accretors, has been studied. They are called intermediate polars (IP) and have been suggested to be the main contributors to the diffuse, hard X-ray emission close to the Galactic center (GC) and in the Galactic bulge (GB), because most of them are unresolved there. Aims. In an ongoing X-ray survey (0.5–10 keV energy band) of 3° × 3° around the GC with the XMM-Newton observatory, we conducted a systematic search for transient X-ray sources. Methods. Promising systems were analyzed for spectral, timing, and multiwavelength properties to constrain their nature. Results. We discovered a new highly variable (factor ≳20) X-ray source about 1.25° south of the GC. We found evidence that makes the newly discovered system a candidate IP. The X-ray light curve shows a period of 511 ± 10 s, which can be interpreted as the spin period of the WD. The X-ray spectrum is well fit by a bremsstrahlung model with a temperature of 13.9 ± 2.5 keV, suggesting a WD mass of 0.4−0.5 M⊙. We were unable to identify a blue optical counterpart in any of the candidate sources, as would be expected for IPs. Conclusions. The high X-ray absorption and absence of a clear optical counterpart suggest that the source is most likely located in the GB. This would make the system a transient IP (GK Per class) with an especially high peak X-ray luminosity, which means that it is a very faint X-ray transient.

scholarly journals The Cyclotron Lines in the Optical Spectra of the Stars of AM Herculis Group: Observations and Interpretation

1980 ◽  
Vol 88 ◽  
pp. 453-465 ◽  
Author(s):  
I. G. Mitrofanov
Keyword(s):  
Magnetic Field ◽  
Cataclysmic Variables ◽  
Magnetized Plasma ◽  
Close Binaries ◽  
X Rays ◽  
Observational Method ◽  
Ultraviolet Continuum ◽  
X Ray ◽  
Optical Continuum ◽  
Basic Prediction

The stars of the AM Herculis group (AM Her, VV Pup, AN UMa and 2A 0311-227) are close binaries containing a mass losing, nondegenerate star and an accreting degenerate dwarf. Their main properties are: the large linear and circular polarization of the optical light, high and low luminosity states, the variable emission line, spectra of H, He and other elements and the identification of these objects with X-ray sources. It is generally accepted that the strong magnetic field of the degenerate dwarf is responsible for these peculiar properties and for the distinction between these objects and the cataclysmic variables (Mitrofanov 1978, 1979a). The polarized optical continuum may be emitted by the accreted magnetized plasma (e.g. Chanmugam and Wagner, 1979), by the magnetized photosphere of the degenerate dwarf (Mitrofanov et al. 1977), or by both sources (Mitrofanov, 1979b). To explain the observed X-rays, Lamb and Masters (1979) showed that a magnetic field about 108 gs is necessary. Unfortunately, the basic prediction of their model - the strong ultraviolet continuum in the spectrum of AM Herculis - appears to be absent (Raymond et al. 1979). Chanmugam and Wagner (1979) proposed a rather different estimate for B of 2 · 108/m*gs (m* = 5 ÷ 25). For further investigations of the AM Herculis-type stars it seems useful to find a direct observational method for measuring the dwarfs′ magnetic fields.

scholarly journals Monitoring of X-Ray Sources in the Optical Spectral Region

2010 ◽  
Vol 2010 ◽  
pp. 1-12
Author(s):  
Vojtěch Šimon
Keyword(s):  
Gamma Ray ◽  
Cataclysmic Variables ◽  
Physical Processes ◽  
X Ray ◽  
Low Mass ◽  
Intermediate Polars ◽  
Photometric Monitoring ◽  
The Individual ◽  
X Ray Binaries ◽  
Review Current

We review current results and perspectives of the photometric monitoring of the optical counterparts of X-ray sources of various kinds (binary X-ray sources (cataclysmic variables and low-mass X-ray binaries, supersoft X-ray sources, microquasars), gamma-ray bursts). We discuss the problems of the monitoring of the individual kinds of objects in the optical and X-ray passbands. We show the importance of multifilter monitoring to obtain a deeper understanding of the physical processes and to resolve between the individual emission mechanisms. We also show that there are brief, unique, and little understood phenomena which are very promising targets for the optical monitoring, for example, flares in intermediate polars.

scholarly journals Cataclysmic Variables — X-rays and Optical Activity in V1223 Sgr and V709 Cas

10.14311/1464 ◽  
2011 ◽  
Vol 51 (6) ◽  
Author(s):  
R. Gális ◽  
L. Hric ◽  
E. Kundra ◽  
F. Münz
Keyword(s):  
Optical Activity ◽  
Cataclysmic Variables ◽  
Galactic Centre ◽  
Source Population ◽  
X Rays ◽  
Major Fraction ◽  
X Ray ◽  
Physical Mechanisms ◽  
Intermediate Polars ◽  
Activity State

Intermediate polars are a major fraction of all cataclysmic variables detected by INTEGRAL in hard X-ray. These objects have recently been proposed to be the dominant X-ray source population detected near the Galactic centre, and they also contribute significantly to X-ray diffuse Galactic ridge emission. Nevertheless, only 25% of all known intermediate polars have been detected in hard X-ray. This fact can be related to the activity state of these close interacting binaries.A multi-frequency (from optical to X-ray) investigation of intermediate polars is essential for understanding the physical mechanisms responsible for the observed activity of these objects.

Sign in / Sign up

Export Citation Format

Share Document