scholarly journals Broad-Band Variability in Accreting Compact Objects

2015 ◽  
Vol 2 (1) ◽  
pp. 107-110 ◽  
Author(s):  
S. Scaringi
Keyword(s):  
Accretion Disk ◽  
Broad Band ◽  
Cataclysmic Variables ◽  
Compact Object ◽  
Variable Stars ◽  
Compact Objects ◽  
Time Lags ◽  
Disk Model ◽  
X Ray ◽  
X Ray Binaries

Cataclysmic variable stars are in many ways similar to X-ray binaries. Both types of systems possess an accretion disk, which in most cases can reach the surface (or event horizon) of the central compact object. The main difference is that the embedded gravitational potential well in X-ray binaries is much deeper than those found in cataclysmic variables. As a result, X-ray binaries emit most of their radiation at X-ray wavelengths, as opposed to cataclysmic variables which emit mostly at optical/ultraviolet wavelengths. Both types of systems display aperiodic broad-band variability which can be associated to the accretion disk. Here, the properties of the observed X-ray variability in XRBs are compared to those observed at optical wavelengths in CVs. In most cases the variability properties of both types of systems are qualitatively similar once the relevant timescales associated with the inner accretion disk regions have been taken into account. The similarities include the observed power spectral density shapes, the rms-flux relation as well as Fourier-dependant time lags. Here a brief overview on these similarities is given, placing them in the context of the fluctuating accretion disk model which seeks to reproduce the observed variability.

scholarly journals Pulsational Instability of Accretion Disks around Compact Objects

1993 ◽  
Vol 134 ◽  
pp. 361-364
Author(s):  
T. Okuda ◽  
S. Mineshige
Keyword(s):  
Accretion Disks ◽  
Cataclysmic Variables ◽  
Compact Object ◽  
Linear Analysis ◽  
Compact Objects ◽  
Periodic Oscillations ◽  
X Ray ◽  
Axisymmetric Perturbation ◽  
Low Mass ◽  
X Ray Binaries

AbstractLinear analysis shows that radial oscillations in accretion disks around compact object are overstable to axisymmetric perturbation under a variety of conditions. Furthermore, numerical simulations confirm that the radial oscillations induce quasi-periodic modulations of the disk luminosity. The disk oscillation model may be responsible for quasi-periodic oscillations (QPOs) observed in low mass X-ray binaries (LMXBs), cataclysmic variables (CVs), and other compact objects.

scholarly journals Theory of Accretion Disk Coronae

1990 ◽  
Vol 115 ◽  
pp. 187-196
Author(s):  
T. R. Kallman
Keyword(s):  
Active Galactic Nuclei ◽  
Accretion Disk ◽  
Cataclysmic Variables ◽  
Galactic Nuclei ◽  
X Ray ◽  
Spectral Signatures ◽  
Low Mass ◽  
X Ray Absorption ◽  
X Ray Binaries ◽  
Theoretical Issues

AbstractAccretion disk coronae are likely to be the dominant site for X-ray absorption and reprocessed emission in low mass X-ray binaries, and may be present in other classes of compact X-ray sources such as active galactic nuclei and cataclysmic variables. In spite of this fact, and in spite of the observational evidence for their existence, there remain many uncertainties about the structure of accretion disk coronae. This paper will discuss the coronal structure and dynamics, their X-ray spectral signatures including coupling to the variability behavior of compact X-ray sources, and the major unsolved theoretical issues surrounding them.

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 DIVISION V: VARIABLE STARS

2008 ◽  
Vol 4 (T27A) ◽  
pp. 251-253
Author(s):  
Alvaro Giménez ◽  
Steven D. Kawaler ◽  
Conny Aerts ◽  
Jørgen Christensen-Dalsgaard ◽  
Michael Breger ◽  
...  
Keyword(s):  
Binary System ◽  
Cataclysmic Variables ◽  
Variable Stars ◽  
Eclipsing Binaries ◽  
Close Binaries ◽  
X Ray ◽  
Pulsating Stars ◽  
Interacting Systems ◽  
Detached Binaries ◽  
X Ray Binaries

Division V deals with all aspects of stellar variability, either intrinsic or due to eclipses by its companion in a binary system. In the case of intrinsic stellar variability the analysis of pulsating stars, surface inhomogeneities, stellar activity and oscillations are considered. For close binaries, classical detached eclipsing binaries are studied as well as more interacting systems, like contact and semi-detached binaries, or those with compact components, like cataclysmic variables and X-ray binaries, including the physics of accretion processes.

scholarly journals Measuring the Masses of Compact Objects in Low-Mass X-Ray Binaries

2004 ◽  
Vol 194 ◽  
pp. 214-214
Author(s):  
Dawn M. Gelino
Keyword(s):  
Black Hole ◽  
Neutron Star ◽  
Compact Object ◽  
Compact Objects ◽  
Orbital Inclination ◽  
X Ray ◽  
Secondary Star ◽  
Low Mass ◽  
The Masses ◽  
X Ray Binaries

Low-mass X-ray binaries (LMXBs) contain compact, black hole (BH) or neutron star (NS) primaries, and cool, low-mass secondary stars. We measure the orbital inclination of the system in quiescence by modeling infrared (IR) ellipsoidal variations from the secondary star in order to determine the compact object mass. I present our results for a few LMXBs, including the first BH that appears to conclusively fall in the 3-5 M⊙ range.

scholarly journals Accretion Onto the Neutron Star in Be/X-ray Binaries

2004 ◽  
Vol 218 ◽  
pp. 449-450
Author(s):  
Kimitake Hayasaki ◽  
Atsuo T. Okazaki
Keyword(s):  
Neutron Star ◽  
High Resolution ◽  
Accretion Disk ◽  
Time Dependent ◽  
Disk Model ◽  
X Ray ◽  
Short Period ◽  
Be Star ◽  
X Ray Binaries ◽  
Resolution Simulation

We study accretion onto the neutron star in Be/X-ray binaries, using a 3D SPH code and the data imported from a high resolution simulation by Okazaki et al. (2002) for a coplanar system with a short period (Porb = 24.3 d) and moderate eccentricity (e = 0.34). We find that a time-dependent accretion disk is formed around the neutron star in Be/X-ray binaries. The disk shrinks after the periastron passage of the Be star and restores its radius afterwards. Our simulations show that the truncated Be disk model for Be/X-ray binaries is consistent with the observed X-ray behavior.

scholarly journals The Broad Band X-Ray Telescope (BBXRT) on Astro-1

1990 ◽  
Vol 123 ◽  
pp. 294-294
Author(s):  
P.J. Serlemitsos
Keyword(s):  
Space Shuttle ◽  
Broad Band ◽  
Cataclysmic Variables ◽  
Compact Objects ◽  
X Ray ◽  
Reduction Techniques ◽  
Timing Resolution ◽  
Space Shuttle Columbia ◽  
The Many ◽  
Galactic Sources

AbstractBBXRT is one of four pointed instruments comprising NASA’s Astro-1 mission, currently scheduled for a 9–10 day flight in May 1990 on board the Space Shuttle Columbia. X-ray Spectra of over 150 sources will be obtained in the energy range 0.3 to 12 keV, with energy resolution of ~100 eV FWHM and timing resolution of 64 μS. BBXRT’S large throughput, broad band mirrors, coupled to segmented cooled Si(Li) detectors, give us the first opportunity to study in detail X-ray spectral features, from oxygen to the iron K band. In developing this instrument, we have made extensive use of detector background reduction techniques in order to be able to observe the many faint extra-galactic sources discovered with the Einstein observatory. Sources in our observing plan have been selected to give us in a 2–4 ks observation < 103 net counts with negligible background. Specific scientific objectives range from refinements of spectra previously obtained at lower resolution, such as a search for relativistic line shifts in compact objects, to observations of faint extragalactic sources for which spectral information is, at best, sketchy, viz. elliptical galaxies and distant quasars. High on our priorities are a search for emission from SN1987A and the first simultaneous observations in the UV and X-ray band of selected sources such as cataclysmic variables and late-type stars.

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&gt; 10 keV is likely due to fluorescence outside the He II ionization front.

scholarly journals X-Ray Determination of the Black-Hole Mass in Cygnus X-1

1998 ◽  
Vol 188 ◽  
pp. 388-389
Author(s):  
A. Kubota ◽  
K. Makishima ◽  
T. Dotani ◽  
H. Inoue ◽  
K. Mitsuda ◽  
...  
Keyword(s):  
Black Hole ◽  
Compact Object ◽  
Optical Observations ◽  
Black Hole Mass ◽  
X Ray ◽  
Upper Limit ◽  
Supergiant Star ◽  
X Ray Binaries ◽  
Two Bodies

About 10 X-ray binaries in our Galaxy and LMC/SMC are considered to contain black hole candidates (BHCs). Among these objects, Cyg X-1 was identified as the first BHC, and it has led BHCs for more than 25 years(Oda 1977, Liang and Nolan 1984). It is a binary system composed of normal blue supergiant star and the X-ray emitting compact object. The orbital kinematics derived from optical observations indicates that the compact object is heavier than ~ 4.8 M⊙ (Herrero 1995), which well exceeds the upper limit mass for a neutron star(Kalogora 1996), where we assume the system consists of only two bodies. This has been the basis for BHC of Cyg X-1.

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