相关论文: A microquasar classification from a disk instabili…

The instability in protoplanetary disks due to gas-dust friction and self-gravity of gas and dust is investigated by linear analysis. In the case where the dust to gas ratio is enhanced and turbulence is week, the instability grows, even in…

The two galactic `microquasars' with superluminal radio jets have been quite active during 1996, generatinga variety of studies involving both NASA and ground-based observatories. GRS~1915+105 has displayed dramatic accretion instability in…

We report on the numerical discovery of quasi-periodic oscillations (QPOs) associated with accretion through a non-axisymmetric magnetic boundary layer in the unstable regime, when two ordered equatorial streams form and rotate…

High-frequency twin peak quasiperiodic oscillations (QPOs) are observed in four microquasars, i.e., Galactic black hole binary systems, with frequency ratio very close to 3:2. In the microquasar GRS 1915+105, the structure of QPOs exhibits…

We show that the galactic microquasar GRS 1915+105 exhibits quasi-periodic oscillations (QPOs) whose frequency varies continuously from 1-15 Hz, during spectrally hard dips when the source is in a flaring state. We report here analyses of…

Analytical treatment of black hole accretion generally presumes the stability of the stationary configuration. Various authors in the past several decades demonstrated the validity of such an assumption for inviscid hydrodynamic flow.…

Low-mass condensations (LMCs) are observed inside the envelope of the collapsing molecular cloud cores. In this research, we investigate the effects of landing LMCs for occurrence of instability through the protostellar accretion disks. We…

The microquasar GRS 1915+105 is known to exhibit a very variable X-ray emission on different time scales and patterns. We propose a system of two ordinary differential equations, adapted from the Hindmarsh-Rose model, with two dynamical…

We present in this proceeding some aspects of a model that should explain the spectral state changes observed in microquasars. In this model, ejection is assumed to take place only in the innermost disc region where a large scale magnetic…

In most microquasars, low-frequency quasi-periodic oscillations (LFQPO) have been classified into three types (A, B and C depending on the peak distribution in the PDS and the shape of the noise) but no explanation has been proposed yet.…

Measurement of the energy emitted from accreting astrophysical systems provides an observational constraint on the plasma processes that may be operating within the disk. Here we examine the continual time variation over the past six years…

We present a set of new characteristic frequencies associated with accretion disks around compact objects. These frequencies arise from persistent rotating patterns in the disk that are finite in radial extent and driven purely by the…

Low mass, self-gravitating accretion disks admit quasi-steady,`gravito-turbulent' states in which cooling balances turbulent viscous heating. However, numerical simulations show that gravito-turbulence cannot be sustained beyond dynamical…

We study rapidly accreting, gravitationally unstable disks with a series of global, three dimensional, numerical experiments using the code ORION. In this paper we conduct a numerical parameter study focused on protostellar disks, and show…

Low Mass X-Ray Binaries (LMXBs) are systems in which a compact object accretes from a binary companion star via an accretion disk. The X-ray properties of LMXBs show strong variability over timescales ranging from milliseconds to decades,…

Microquasars are the compact objects generally including accreting black holes which produce relativistic jets. The physical mechanisms of jet launching, collimation, and acceleration are poorly understood. Microquasars show strong…

During the final growth phase of giant planets, accretion is thought to be controlled by a surrounding circumplanetary disk. Current astrophysical accretion disk models rely on hydromagnetic turbulence or gravitoturbulence as the source of…

Understanding how accretion proceeds in proto-planetary discs and more generally their dynamics is a crucial issue for explaining the conditions in which planets form. The role that accretion of gas from the surrounding molecular cloud onto…

The Vertical Shear Instability is one of two known mechanisms potentially active in the so-called dead zones of protoplanetary accretion disks. A recent analysis indicates that a subset of unstable modes shows unbounded growth - both as…

The Accretion-Ejection Instability has been proposed to explain the low frequency Quasi-Periodic Oscillation (QPO) observed in low-mass X-Ray Binaries, in particular Black-Hole candidates. Its frequency, typically a fraction of the…