We present results of 3D simulations of MHD instabilities at the accretion diskmagnetosphere boundary. The instability is Rayleigh-Taylor, and develops for a fairly broad range of accretion rates and stellar rotation rates and magnetic fields. It manifests itself in the form of tall, thin tongues of plasma that penetrate the magnetosphere in the equatorial plane. The shape and number of the ton...

It has been suggested that the final stages of accretion in present–day giant elliptical galaxies occur in an advection-dominated mode. The poor radiative efficiency of this accretion solution accounts for the fact that massive black holes, which are believed to reside in the centres of these galaxies, do not have the luminosities expected if accretion from the hot interstellar medium occurs at...

Compton scattering within the accretion column of magnetic cataclysmic variables (mCVs) can induce a net polarization in the X-ray emission. We investigate this process using Monte Carlo simulations and find that significant polarization can arise as a result of the stratified flow structure in the shock-ionized column. We find that the degree of linear polarization can reach levels up to ∼ 8% ...

Using a generalized non-spherical, multi-transonic accretion flow model, we analytically calculate the normalized QPO frequency νqpo of galactic black hole candidates in terms of dynamical flow variables and self-consistently study the dependence of νqpo on such variables. Our results are in fairly close agreement with the observed QPO frequencies of GRS 1915+105. We find that νqpo is quite sen...

We obtained global transonic solutions representing optically thin advectiondominated accretion flow by solving the full set of differential equations describing such systems. We found that far from the sonic point self-similar solutions are an excellent approximation of the global flow structure if the accretion rate is well below the maximum value above which no optically thin solutions exist...

Formation of massive stars by accretion requires a high accretion rate of Ṁ∗ > 10 −4 M⊙/yr to overcome the radiation pressure barrier of the forming stars. Here, we study evolution of protostars accreting at such high rates, by solving the structure of the central star and the inner accreting envelope simultaneously. The protostellar evolution is followed starting from small initial cores until...

The wetlands of the southern Louisiana coast are disappearing due to a host of environmental stressors. Thus, it is imperative to analyze the spatial and temporal variability of wetland vertical accretion rates. A key question in accretion concerns the role of landfalling hurricanes as a land-building agent, due to their propensity to deposit significant volumes of inorganic sediments. Since 19...

The Mira AB interacting binary provides an ideal laboratory for studying mass loss and accretion processes in systems containing an AGB star and a compact accretor, because its components have been resolved and can be studied individually. We present here results from our long term study of accretion processes in this system. These include recent HST observations suggesting that the accretion r...

Accretion-deletion is widely considered a decisive cue to surface depth ordering, with the accreting or deleting surface interpreted as behind an adjoining surface. However, Froyen, Feldman, and Singh (2013) have shown that when accretion-deletion occurs on both sides of a contour, accreting-deleting regions can also be perceived as in front and as self-occluding due to rotation in three dimens...

Observations of the H66α recombination line from the ionized gas in the cluster of newly formed massive stars, G10.6–0.4, show that most of the continuum emission derives from the dense gas in an ionized accretion flow that forms an ionized disk or torus around a group of stars in the center of the cluster. The inward motion observed in the accretion flow suggests that despite the equivalent lu...