The Ultra-luminous Compact X-ray Sources (ULXs) in nearby spiral galaxies and the Galactic superluminal jet sources share the common spectral characteristic that they have extremely high disk temperatures which cannot be explained in the framework of the standard accretion disk model in the Schwarzschild metric. We examine several possibilities to solve this “too-hot” disk problem. In particula...

We report on an observation of the Galactic black hole candidate GRS 1739−278 during its 2014 outburst, obtained with NuSTAR. The source was captured at the peak of a rising “low/hard” state, at a flux of ∼ 0.3 Crab. A broad, skewed iron line and disk reflection spectrum are revealed. Fits to the sensitive NuSTAR spectra with a number of relativistically blurred disk reflection models yield str...

Massive protostars evolve from hot cores to ultra-compact H II regions and eventually form classical H II regions; however, details of this evolution are far from understood. A few years ago, a new class of exceptionally small and dense objects, so-called hyper-compact H II regions, was discovered. They are believed to represent a transitional stage in early massive stellar evolution. Thus, the...

We examine the reprocessing of X-ray radiation from compact objects by accretion disks when the X-ray emission from the star is highly beamed. The reprocessed flux for various degrees of beaming and inclinations of the beam axis with respect to the disk is determined. We find that, in the case where the beam is produced by a non-relativistic object, the intensity of the emitted spectrum is high...

In order to further test our hypothesis that jets and disk around compact accreting objects are symbi-otic features we investigate the newly discovered superlu-minal galactic radio jets GRS 1915+105 and GRO J1655-40 and other galactic radio jets like 1E1740-2942, GRS 1758-258 and SS 433 within the framework of our coupled jet/disk model developed initially for active galactic nuclei (AGN) and t...

We present the first results of coordinated multi-wavelength observations of the Galactic black hole GX 339−4 in a canonical low–hard state, obtained during its 2004 outburst. XMM-Newton observed the source for 2 revolutions, or approximately 280 ksec; RXTE monitored the source throughout this long stare. The resulting data offer the best view yet obtained of the inner accretion flow geometry i...

An accretion flow is necessarily transonic around a black hole. However, around a neutron star it may or may not be transonic, depending on the inner disk boundary conditions influenced by the neutron star. I will discuss various transonic behavior of the disk fluid in general relativistic (or pseudo general relativistic) framework. I will address that there are four types of sonic/critical poi...

We show that Brennan’s conjecture is equivalent to the existence of self-maps of the unit disk that make certain weighted composition operators compact.