As a star is evolving from the hydrogen to the helium burning stage, i. e. from the sun-like state to the state of a red-giant star, the temperature of its core increases whereas the volume decreases. At the same time the temperature of its shell decreases while the volume of the shell increases. This behaviour of the core and of the shell is explained qualitatively by a simple model. The star ...

We have detected asymmetry in the symbiotic star CH Cyg through the measurement of precision closure phase with the Integrated Optics Near-Infrared Camera (IONIC) beam combiner, at the infrared optical telescope array interferometer. The position of the asymmetry changes with time and is correlated with the phase of the 2.1-year period found in the radial velocity measurements for this star. We...

With a peak luminosity of ∼ 1047 erg s−1, the December 27th 2004 giant flare from SGR1806-20 would have been visible by BATSE (the Burst and Transient Source Experiment) out to ≈ 50 Mpc[1, 2]. It is thus plausible that some fraction of the short duration Gamma-Ray Bursts (sGRBs) in the BATSE catalogue were due to extragalactic magnetar giant flares. According to the most widely accepted current...

The possible origin of two low-mass hyper-iron-poor (HIP) stars, HE0107-5240 and HE13272326 are investigated. The three scenarios tested are as follows. (i) The star forms metal free (Population III) and accretes metals throughout its lifetime. (ii) A Population III binary star system forms, and the lower mass star accretes metals from the higher mass star during its asymptotic giant branch pha...

This paper extends our previous study of planet/brown dwarf accretion by giant stars to solar mass stars located on the red giant branch. The model assumes that the planet is dissipated at the bottom of the convective envelope of the giant star. The giant’s evolution is then followed in detail. We analyze the effects of different accretion rates and different initial conditions. The computation...

Context. For the past 3 years we have been monitoring a sample of 62 K giant stars using precise stellar radial velocity measurements with high accuracy taken at the Thüringer Landessternwarte Tautenburg. Aims. To search for sub-stellar companions to giant stars and to understand the nature of the diverse radial velocity variations exhibited by K giant stars. Methods. We present precise stellar...

We investigate the tidal interactions of a red giant with a main sequence in the dense stellar core of globular clusters by Smoothed Particle Hydrodynamics method. Two models of 0.8M⊙ red giant with the surface radii 20 and 85R⊙ are used with 0.6 or 0.8M⊙ main sequence star treated as a point mass. We demonstrate that even for the wide encounters that two stars fly apart, the angular momentum o...

We examine the origins of the bimodality observed in the global properties of galaxies by comparing the environmental dependencies of star-formation for giant and dwarf galaxy populations. Using Sloan Digital Sky Survey (SDSS) DR4 spectroscopic data to create a volume-limited sample complete to M ⋆ + 3, we find that the environmental dependences of giant and dwarf galaxies are quite different, ...

We simulate collisions involving red-giant stars in the centre of our galaxy. Such encounters may explain the observed paucity of highly luminous red giants within ∼ 0.2 pc of Sgr A⋆. The masses of the missing stars are likely to be in the range ∼ 2M⊙ − 8M⊙. Recent models of the galactic centre cluster’s density distribution and velocity dispersion are used to calculate two-body collision rates...

We examine the origins of the bimodality observed in the global properties of galaxies around a stellar mass of 3×10M⊙ by comparing the environmental dependencies of star-formation for the giant and dwarf galaxy populations. The Sloan Digital Sky Survey DR4 spectroscopic dataset is used to produce a sample of galaxies in the vicinity of the supercluster centered on the cluster A2199 at z = 0.03...