Context. Extrasolar giant planets are found to orbit their host stars with a broad range of semi-major axes 0.02 ≤ a ≤ 6 AU. Current theories suggest that giant planets orbiting at distances between ≃ 0.02 – 2 AU probably formed at larger distances and migrated to their current locations via type II migration, disturbing any inner system of forming terrestrial planets along the way. Migration p...

Based on the spectra obtained with Infrared Space Observatory, ISO, we detected the 6.3μm bands of water in the late K giant Aldebaran (α Tau) and several early M giant stars (between M0 and M3.5), which have been deemed to be too warm for tri-atomic H2O molecule to reside in their photospheres. The water column densities range (0.2− 2)× 10 molecules cm in our sample of K and M giant stars and ...

We report high-precision, high-cadence photometric measurements of the star HD 209458, which is known from radial velocity measurements to have a planetary-mass companion in a close orbit. We detect two separate transit events at times that are consistent with the radial velocity measurements. In both cases, the detailed shape of the transit curve due to both the limb darkening of the star and ...

We employ an effective gravitational stellar final collapse model which contains the relevant physics involved in this complex phenomena: spherical radical infall in the Schwarzschild metric of the homogeneous core of an advanced star, giant magnetic dipole moment, mag-netohydrodynamic material response and realistic equations of state (EOS). The electromagnetic pulse is computed both for mediu...

We summarize and analyze the available observational data on the progenitor and the enviroment of V838 Mon, the object that erupted in January 2002. We show that the radio and infrared observed matter in the vicinity of V838 Mon could not have its origin in mass loss from V838 Mon but is of interstellar origin. Also from the light echo evolution we conclude that the reflecting dust is of the sa...

One possible mechanism for giant planet formation is disk instability in which the planet is formed as a result of gravitational instability in the protoplanetary disk surrounding the young star. The final composition and core mass of the planet will depend on the planet’s mass, environment and the planetesimal accretion efficiency. We calculate heavy element enrichment in a Jupiter-mass protop...

Earlier works, which we review, have shown that if the Fe core in a presupernova star is to be sufficiently massive to collapse into a black hole, earlier in the evolution of the star the He core must be covered (clothed) by a hydrogen envelope during He core burning and removed only following this, in, e.g. common envelope evolution. This is classified as Case C mass transfer. These previous a...

Giant flares can release large amounts of energy within a few days 1−7 : X-ray emission alone can be up to ten percent of the star's bolometric luminosity. These flares exceed the luminosities of the largest solar flares by many orders of magnitude, which suggests that the underlying physical mechanisms supplying the energy are different from those on the Sun. Magnetic coupling between the comp...

While the recent microlensing discoveries of super-Earths orbiting two M dwarf stars have been taken as support for the core accretion mechanism of giant planet formation, we show here that these planets could also have been formed by the competing mechanism of disk instability, coupled with photoevaporative loss of their gaseous envelopes by a strong external source of UV radiation, i.e., an O...

PSR J1811−1736 (P = 104 ms) is a binary pulsar in a highly eccentric orbit (P orb = 18.8 d) around an unidentified companion. Here, an optical follow-up investigation of the pulsar field, performed using photographic plates from the UK-SERC Equatorial red survey, is reported. No object is detected at the pulsar position down to R ∼ 22. At the pulsar distance of 6 kpc, this implies, for a likely...