The geometry of black hole spacetimes can be probed with exquisite precision in the gravitational-wave window, and possibly also optical regime. We study accretion bright spots---objects which emit strongly or gravitational waves---by nonspinning holes. As object approaches event horizon, emitted radiation to far-away distances is dominated by photons gravitons orbiting light ring, causing tota...

We briefly review recent theoretical studies of the effects of accreted envelopes, magnetic fields and crustal superfluidity on the cooling of neutron stars. These effects are especially important for slowly cooling low-mass neutron stars, where direct Urca process of neutrino emission is forbidden. The effects are useful for interpretation of observations of several isolated middle-aged neutro...

Using two-dimensional simulations of non-radiative viscous rotating black hole accretion flows, we show that the flows with α ∼ 0.1 − 0.3 self-organize to form stationary unipolar or bipolar outflows accompanied by global meridional circulations. The required energy comes, with efficiency ∼ 0.001 − 0.01, from the matter directly accreted onto black hole. Observational implications are discussed.

Atopophlebia pitculya is described from adults and nymphs from western Ecuador. Nymphs were found in leaf packs in small streams that can be intermittent in the dry season. This species along with Atopophlebia fortunensis are found associated with the accreted terranes of Central America, the Western Andes of Colombia, and the coastal mountains in northwestern Ecuador.

We have investigated the physical conditions under which accreting neutron stars in low-mass X-ray binaries can both produce and preserve sufficient quantities of carbon fuel to trigger superbursts. Our theoretical models span the plausible ranges of neutron star thermal conductivities, core neutrino emission mechanisms, and areal radii, as well as the CNO abundances in the accreted material. W...

We simulated the behavior of interstellar gas clouds in a companion galaxy during a gas-dynamical interaction with the halo and disk of a spiral galaxy. By ram pressure, the gas clouds are stripped from the companion, and accreted toward the disk of the spiral galaxy. If the companion’s orbit is retrograde with respect to the rotation of the spiral galaxy, infalling clouds hit the nuclear regio...