天体物理学
In this work we would like to address the issue of shock formation in black hole accretion discs. We provide a {\it generalized two parameter solution scheme} for multi-transonic, accretion and wind around Schwarzschild black holes, by…
We discuss the difficulties of forming earth-like planets in metal-poor environments, such as those prevailing in the Galactic halo (Pop II), the Magellanic Clouds, and the early universe. We suggest that, with less heavy elements…
The formation of massive stars is one of the major unsolved problems in stellar astrophysics. However, only few if any of these are found as single stars, on average massive stars have more than one companion. Many of them are born in dense…
We propose a near-infrared microlensing survey of the central 2 degree field of the Galactic Center, in an attempt to estimate the surface density and mass distribution of distant free-floating brown dwarfs in the bulge and in the disk,…
In the first three years of operation STIS obtained slitless spectra of approximately 2500 fields in parallel to prime HST observations as part of the STIS Parallel Survey (SPS). The archive contains almost 300 fields at high galactic…
We investigate dynamical response on size and velocity dispersion to mass loss by supernovae in formation of two-component spherical galaxies composed of baryon and dark matter. Three-dimensional deprojected de Vaucouleurs-like and…
We investigate the effect that the structure of GRB jets has on the afterglow light curves for observers located at different viewing angles, $\theta_{obs}$, from the jet symmetry axis. The largest uncertainty in the jet dynamics is the…
The influence of a linearized perturbation on stationary inflow solutions in an inviscid and thin accretion disc, has been studied here, and it has been argued, that a perturbative technique would indicate that all possible classes of…
A major goal of contemporary astrophysics is understanding the origin of the most massive galaxies in the universe, particularly nearby ellipticals and spirals. Theoretical models of galaxy formation have existed for many decades, although…
We report the first results of the Chandra temporal monitoring of the ultra-luminous X-ray sources (ULXs) in the Antennae galaxies (NGC 4038/39). Observations at four different epochs, covering time scales of 2 years to 2 months, show…
EUSO experiment, while monitoring the downward Earth atmosphere layers, may observe among common Ultra High Energy Cosmic Rays, UHECR, also High Energy Neutrino-Induced Showers either blazing upward to the detectors at high (PeVs) energies…
In the 60s and 70s super-massive central objects (from now onwards SMOs) were thought to be the main source of active galactic nuclei (AGNs) characteristics (luminosities of $L \approx 10^{12} L_{\odot}$). The release of gravitational…
Collapse of the rotating spheroid is approximated by a system of ordinary differential equations describing its dynamics. The gravitational potential is approximated by the one of the iniform Maclaurin spheroid. Developement of…
We propose to use a high throughput and high precision multi-object dispersed fixed-delay interferometer for all sky Doppler surveys for extrasolar planets. This instrument, a combination of a fixed-delay interferometer with a moderate…
Analyses of stellar spectra often begin with the determination of a number of parameters that define a model atmosphere. This work presents a prototype for an automated spectral classification system that uses a 15 nm-wide region around…
Up to half of the baryons inferred to once have been in our galaxy have not yet been detected. Ejection would seem to provide the most attractive explanation. Previous numerical studies may have underestimated the role of winds. I propose a…
A catalog of optical warps of galaxies is presented. This can be considered complementary to that reported by Sanchez-Saavedra et al., with 42 galaxies in the northern hemisphere, and to that by Reshetnikov & Combes, with 60 optical warps.…
The spectrum of neutrinos produced by the outflow of high temperature matter surrounding microscopic black holes is calculated for neutrino energies between one GeV and the Planck energy. The results may be applicable for the last few hours…
The evolution of cosmological large-scale perturbations is described in terms of the concordant model based on the recent discovery of cosmic vacuum. It is demonstrated that the process is robustly controlled by a few epoch-independent…
I present preliminary BV resolved stellar photometry of the M31 disk measured from the data set of the NOAO/CTIO Local Group Survey. I have performed detailed analyses of the star formation histories in and around three currently active…