scholarly journals The Intermediate Polars

1983 ◽  
Vol 72 ◽  
pp. 155-172
Author(s):  
Brian Warner
Keyword(s):  
Magnetic Fields ◽  
White Dwarf ◽  
Variable Star ◽  
Theoretical Models ◽  
Cataclysmic Variable ◽  
General Role ◽  
X Ray ◽  
Low Mass ◽  
Intermediate Polars ◽  
X Ray Binaries

Until 1976, cataclysmic variable star research proceeded with few requirements for the inclusion of magnetic fields in theoretical models. Although models for low-mass X-ray binaries stressed the importance of magnetic fields (Lamb et at. 1973) and there was an increasing number of known magnetic single white dwarfs (Angel 1977), and a magnetised white dwarf had been one of the models proposed to explain the rapid oscillations in DQ Her (Herbst et al. 1974, Katz 1975), there was no anticipation of the more general role that magnetic fields now seem destined to play. The two major reviews of the time (Robinson 1976, Warner 1976) scarcely considered the presence of magnetic fields.

scholarly journals Modeling He-Rich Disks in AM CVn Binaries

2004 ◽  
Vol 194 ◽  
pp. 228-228
Author(s):  
T. Nagel ◽  
S. Dreizler ◽  
T. Rauch ◽  
K. Werner
Keyword(s):  
Accretion Disk ◽  
Time Scales ◽  
Accretion Disks ◽  
White Dwarf ◽  
Cataclysmic Variables ◽  
X Ray ◽  
Synthetic Spectra ◽  
Pure Helium ◽  
Low Mass ◽  
X Ray Binaries

We have developed a new code for the calculation of synthetic spectra and vertical structures of accretion disks in cataclysmic variables and compact X-ray binaries. Here we present results for the CV system AM CVn.AM CVn stars are a special type of cataclysmic variables, also called helium cataclysmics. They are systems of interacting binary white dwarfs, consisting of a degenerate C-O white dwarf primary and a low mass semi-degenerate secondary. The secondary loses mass, almost, pure helium, to the primary, forming an accretion disk. They have all in common a helium-rich composition, analoguous to the hydrogen-rich cataclysmic variables. They show photometric variabilities on time scales of ~ 1000s, the prototype of the class, AM CVn, e.g. exhibits a variability of ~ 18 min (Nelemans et al. 2001).

scholarly journals Dwarf Nova Oscillations and Quasi-Periodic Oscillations: Extension of the Two-QPO Diagram of X-Ray Binaries, and a new kind of DNO

2004 ◽  
Vol 190 ◽  
pp. 85-90
Author(s):  
Brian Warner ◽  
Patrick A. Woudt
Keyword(s):  
White Dwarf ◽  
Cataclysmic Variable ◽  
Periodic Oscillations ◽  
X Ray ◽  
Dwarf Nova ◽  
X Ray Binaries

AbstractSeventeen examples are given of Cataclysmic Variable (CV) stars possessing both Dwarf Nova Oscillations (DNOs) and Quasi-Periodic Oscillations (QPOs). These form an extension of the X-Ray Two-QPO correlation to frequencies three orders of magnitude lower. We draw attention to the existence of a second type of DNO in CVs, which is probably caused by magnetically channelled accretion onto the white dwarf.

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 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.

Iron K-Line Emission from X-Ray Binaries

1988 ◽  
Vol 102 ◽  
pp. 47-50
Author(s):  
K. Masai ◽  
S. Hayakawa ◽  
F. Nagase
Keyword(s):  
Accretion Disk ◽  
Radiative Recombination ◽  
Characteristic Temperature ◽  
Line Emission ◽  
Ionization Front ◽  
Continuum Radiation ◽  
X Ray ◽  
Low Mass ◽  
X Ray Binaries

AbstractEmission mechanisms of the iron Kα-lines in X-ray binaries are discussed in relation with the characteristic temperature Txof continuum radiation thereof. The 6.7 keV line is ascribed to radiative recombination followed by cascades in a corona of ∼ 100 eV formed above the accretion disk. This mechanism is attained for Tx≲ 10 keV as observed for low mass X-ray binaries. The 6.4 keV line observed for binary X-ray pulsars with Tx> 10 keV is likely due to fluorescence outside the He II ionization front.

scholarly journals QPOs in compact binaries from small scale eruptions in an inner magnetized disk

2020 ◽  
Author(s):  
Nicolas Scepi ◽  
Mitchell C Begelman ◽  
Jason Dexter
Keyword(s):  
Rapid Heating ◽  
Small Scale ◽  
Type B ◽  
Periodic Oscillations ◽  
X Ray ◽  
Compact Binaries ◽  
Heating And Cooling ◽  
Low Mass ◽  
X Ray Binaries ◽  
Standard Disk

Abstract Dwarf novæ (DNe) and low mass X-ray binaries (LMXBs) are compact binaries showing variability on time scales from years to less than seconds. Here, we focus on explaining part of the rapid fluctuations in DNe, following the framework of recent studies on the monthly eruptions of DNe that use a hybrid disk composed of an outer standard disk and an inner magnetized disk. We show that the ionization instability, that is responsible for the monthly eruptions of DNe, is also able to operate in the inner magnetized disk. Given the low density and the fast accretion time scale of the inner magnetized disk, the ionization instability generates small, rapid heating and cooling fronts propagating back and forth in the inner disk. This leads to quasi-periodic oscillations (QPOs) with a period of the order of 1000 s. A strong prediction of our model is that these QPOs can only develop in quiescence or at the beginning/end of an outburst. We propose that these rapid fluctuations might explain a subclass of already observed QPOs in DNe as well as a, still to observe, subclass of QPOs in LMXBs. We also extrapolate to the possibility that the radiation pressure instability might be related to Type B QPOs in LMXBs.

scholarly journals Drifts of the marginally stable burning frequency in the X-ray binaries 4U 1608–52 and Aql X–1

2021 ◽  
Vol 502 (2) ◽  
pp. 1856-1863
Author(s):  
G C Mancuso ◽  
D Altamirano ◽  
M Méndez ◽  
M Lyu ◽  
J A Combi
Keyword(s):  
Frequency Drift ◽  
Soft Or ◽  
Significance Level ◽  
X Ray ◽  
Intermediate States ◽  
Source State ◽  
Nuclear Burning ◽  
Low Mass ◽  
X Ray Binaries ◽  
Stable Burning

ABSTRACT We detect millihertz quasi-periodic oscillations (mHz QPOs) using the Rossi X-ray Time Explorer (RXTE) from the atoll neutron-star (NS) low-mass X-ray binaries 4U 1608–52 and Aql X–1. From the analysis of all RXTE observations of 4U 1608–52 and Aql X–1, we find mHz QPOs with a significance level >3σ in 49 and 47 observations, respectively. The QPO frequency is constrained between ∼4.2 and 13.4 mHz. These types of mHz QPOs have been interpreted as being the result of marginally stable nuclear burning of He on the NS surface. We also report the discovery of a downward frequency drift in three observations of 4U 1608–52, making it the third source that shows this behaviour. We only find strong evidence of frequency drift in one occasion in Aql X–1, probably because the observations were too short to measure a significant drift. Finally, the mHz QPOs are mainly detected when both sources are in the soft or intermediate states; the cases that show frequency drift only occur when the sources are in intermediate states. Our results are consistent with the phenomenology observed for the NS systems 4U 1636–53 and EXO 0748–676, suggesting that all four sources can reach the conditions for marginally stable burning of He on the NS surface. These conditions depend on the source state in the same manner in all four systems.

Sign in / Sign up

Export Citation Format

Share Document