Absorption in the stellar Lyman-alpha (Lyalpha) line observed during the transit of the extrasolar planet HD 209458b in front of its host star reveals high-velocity atomic hydrogen at great distances from the planet. This has been interpreted as hydrogen atoms escaping from the planet's exosphere, possibly undergoing hydrodynamic blow-off, and being accelerated by stellar radiation pressure. En...

Stellar oscillation under the combined influences of incident gravitational wave and radiation loss is studied in a simple toy model. The star is approximated as a uniform density ellipsoid in the Newtonian gravity including radiation damping through quadrupole formula. The time evolution of the oscillation is significantly controlled by the incident wave amplitude h, frequency ν and damping ti...

The formation of massive stars in close binary systems is complicated due to their high radiation pressure, the crowded environment and the expected minimum separation for fragmentation being many times greater than the orbital separation. I discuss how massive star formation can be understood as being due to competitive accretion in stellar clusters. Massive binary systems are then formed due ...

We examine whether massive binary black holes in spherically symmetric bulges of galaxies can achieve coalescence through the emission of gravitational radiation under the action of stellar dynamical processes alone. In particular, we address the importance of the Brownian motion of a binary’s center-of-mass to its continued interaction with stellar orbits that allows it to keep hardening: the ...

We find a new mechanism of neutron star radiation wherein radiation is produced by the stellar interior. The main finding is that neutron star interior is transparent for collisionless electron sound, the same way as it is transparent for neutrinos. In the presence of magnetic field the electron sound is coupled with electromagnetic radiation, such collective excitation is known as a fast magne...

We have studied the UV radiation in the range 180 to 330 nm emitted by several stars with planetary systems, in order to determine the constraints on the habitable zones posed by the radiation levels. The observations were taken from the International Ultraviolet Explorer (IUE) and the Hubble Space Telescope (HST) satellites database. The stellar sample was chosen to cover the range of what are...

This paper offers an interpretation of the photometric and polarimetric variability of UXORs where the star is surrounded by an optically thick, flared circumstellar disk similar to pre-main–sequence disks. A screen of dust sporadically obscures the stellar radiation, causing a minimum of the stellar light. Using a Monte Carlo code developed by Whitney & Hartmann (1992) we compute the polarizat...

The physical nature of ultraluminous x-ray sources is uncertain. Stellar-mass black holes with beamed radiation and intermediate black holes with isotropic radiation are two plausible explanations. We discovered radio emission from an ultraluminous x-ray source in the dwarf irregular galaxy NGC 5408. The x-ray, radio, and optical fluxes as well as the x-ray spectral shape are consistent with be...

It is essential to know galactic emissivity and spectrum of Lyman continuum (LyC) in order to understand the cosmic reionization. Here we consider an escape of nebular LyC from galaxies and examine the consequent spectral energy distribution. It is usually assumed that hydrogen nebular LyC mostly produced by bound-free transitions is consumed within photo-ionized nebulae (so-called “on-the-spot...