相关论文: Microflares in accretion disks
Galactic X-ray emission is a manifestation of various high-energy phenomena and processes. The brightest X-ray sources are typically accretion-powered objects: active galactic nuclei and low- or high-mass X-ray binaries. Such objects with…
Across a large range of scales, accreting sources show remarkably similar patterns of variability, most notably the log-normality of the luminosity distribution and the linear root-mean square (rms)-flux relationship. These results are…
Explaining variability observed in the accretion flows of black hole X-ray binary systems remains challenging, especially concerning timescales less than, or comparable to, the viscous timescale but much larger than the inner orbital period…
Observations suggest that accretion discs in many X-ray binaries are likely flared. An outer edge of the disc intercepts radiation from the central X-ray source. Part of that radiation is absorbed and reemitted in the optical/UV spectral…
Sgr A*, the putative black hole in our Galactic Center (GC), is extraordinary dim in all frequencies. Apparently the black hole is unable to accrete at the Bondi accretion rate for some reason. Another mystery of Sgr A* is the recently…
Observations show a large spread in the luminosities of young protostars, which are frequently explained in the context of episodic accretion. We here test this scenario using numerical simulations following the collapse of a solar mass…
Quasi-periodic eruption (QPE) sources in galactic nuclei are often associated with a stellar object orbiting a supermassive black hole with hours-days period, brought in as an extreme mass-ratio inspiral (EMRI). In the presence of an…
This paper describes eruptive phenomena in pre-main sequence stars. The eruptions of FU Orionis stars have much in common with outbursts in other accreting systems, such as dwarf novae and some symbiotic stars. These common features are…
Emission spectra of hot accretion disks characteristic of advection dominated accretion flow (ADAF) models are investigated for comparison with the brightest ultra-luminous source, X-1, in the galaxy M82. If the spectral state of the source…
We present a detailed study of explosive chromospheric evaporation during a microflare which occurred on 2007 December 7 as observed with the EUV Imaging Spectrometer (EIS) onboard Hinode. We find temperature-dependent upflows for lines…
We show that a certain class of flare models for variability from accretion disk coronae are subject to beam-plasma instabilities. These instabilities can prevent significant direct acceleration and greatly reduce the variable X-ray…
Activity of the nuclei of galaxies and stellar mass systems involving disk accretion to black holes is thought to be due to (1) a small-scale turbulent magnetic field in the disk (due to the magneto-rotational instability or MRI) which…
IPCVs contain a magnetic, rotating white dwarf surrounded by a magnetically truncated accretion disk. To explain their strong flickering X-ray emission, accretion has been successfully taken into account. Nevertheless, observations suggest…
We present a model for the short timescale spectral variability of accreting black holes. It describes well the time-averaged spectra as well as temporal characteristics such as power-density spectrum, time/phase lags, and coherence…
Straight-forward models of X-ray reflection in the inner region of accretion discs predict that primary X-ray flux and the flux reflected off the surface of the disc should vary together, albeit a short light travel time delay. Most of the…
We present time-dependent models of the accretion disks created during compact object mergers, focusing on the energy available from accretion at late times and the composition of the disk and its outflows. We calculate the dynamics near…
Highly-ionized fast accretion-disk winds have been suggested as an explanation for a variety of observed absorption and emission features in the X-ray spectra of Active Galactic Nuclei. Simple estimates have suggested that these flows may…
Using the Rossi X-ray Timing Explorer (RossiXTE), astronomers have discovered that disk-accreting neutron stars with weak magnetic fields produce three distinct types of high-frequency X-ray oscillations. These oscillations are powered by…
Geometrically thick disks may form after tidal disruption events, and rapid accretion may lead to short flares followed by long-term, lower-level emission. Using a novel accretion disk code which relies primarily on global conservation laws…
We examine a new paradigm to account for the exponential decay seen in the light curves of some of the bright X-ray novae. These systems show an exponential decay in soft X-rays with an e-folding time constant of ~30 d. We investigate a…