We present results of a survey of the spectra of Low Mass X-ray Binaries using ASCA. It is shown that all sources in the survey are well-fitted by the same twocomponent emission model that we have previously shown is able to describe both the non-dip and dip spectra of the dipping class of LMXB. This model consists of pointlike blackbody emission from the neutron star plus Comptonized emission ...

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 and the assumption that viscosity is everywhere positive, a broad range of physically allowed evolutionary sequences of thick disks is investigated. The mai...

We calculate the visual light curve of CAL 87 based on the assumption that an accreting steadily burningwhite dwarf irradiates the accretion disk and the secondary star, as suggested by van den Heuvel et al. (1992). We find a reasonable fit including the following sources of visual light: 1. the secondary star where the energy from irradiation is spread out over the surface, 2. the accretion di...

Winds from accretion disks have been proposed as the driving source for precessing jets and extreme bipolar morphologies in Planetary Nebulae (PNe) and proto-PNe (pPNe). In this paper we address the applicability of self-consistent MHD disk wind models to PNe and pPNe. We first review the basic features of magneto-centrifugal launching disk wind models adapting results from previously published...

Many models of gamma-ray bursts (GRBs) involve accretion onto a compact object, usually a black hole, at a mass accretion rate of order a fraction of a solar mass per second. If the accretion disk is larger than a few tens or hundreds of Schwarzschild radii, the accretion will proceed via a convection-dominated accretion flow (CDAF) in which most of the matter escapes to infinity rather than fa...

A fraction of neutrino emission from GRB accretion disks annihilates above the disk, creating e+plasma that can drive GRB explosions. We calculate the efficiency of this annihilation using the recent detailed model of hyper-accretion disks around Kerr black holes. Our calculation is fully relativistic and based on a geodesic-tracing method. We find that the efficiency is a well-defined function...

We study the effects of a thin gaseous accretion disk on the inspiral of a stellar-mass black hole into a supermassive black hole. We construct a phenomenological angular momentum transport equation that reproduces known disk effects. Disk torques modify the gravitational wave phase evolution to detectable levels with LISA for reasonable disk parameters. The Fourier transform of disk-modified w...

The transition of a standard thin disk to a radiatively inefficient accretion flow (RIAF) is expected to occur, when ṁ ∼ ṁcrit (ṁ = Ṁ/ṀEdd). The radiative efficiencies of accretion flows accreting at rates lower than the critical accretion rate ṁcrit become significantly lower than that of standard thin disks. It is believed that the initial transition radius is small just after the accretion m...

We treat transformation properties of external radiation fields in the proper frame of a plasma moving with constant speed. The specific spectral energy densities of external isotropic and accretion-disk radiation fields are derived in the comoving frame of relativistic outflows, such as those thought to be found near black-hole jet and gammaray burst sources. Nonthermal electrons and positrons...