Context. We study the time history of the yellow hypergiant HR 8752 based on high-resolution spectra (1973-2005), the observed MK spectral classification data, B - V- and V-observations (1918-1996) and yet earlier V-observations (1840-1918). Aims: Our local thermal equilibrium analysis of the spectra yields accurate values of the effective temperature (T eff), the acceleration of gravity (g), and the turbulent velocity (v t) for 26 spectra. The standard deviations average are 82 K for T eff, 0.23 for log g, and 1.1 km s -1 for v t. Methods: A comparison of B - V observations, MK spectral

We report the detection of orbital decay in the 12.75-minute, detached binary white dwarf (WD) SDSS J065133.338+284423.37 (hereafter J0651). Our   photometric observations over a 13 month baseline constrain the orbital period to 765.206543 (55) s and indicate that the orbit is decreasing at a rate of  (- 9.8 ± 2.8) ´10 -12 s/s  (or -0.31 ± 0.09 ms/yr). We revise the system parameters based on our new photometric and spectroscopic observations: J0651 contains two WDs with M 1 = 0.26 ± 0.04 M sun and M 2 = 0.50 ± 0.04 M sun.  General relativity predicts orbital decay due to  gravitational wave

The study of the disk rotation curve of our Galaxy at large distances provides an interesting scenario for us to test whether magnetic fields should be considered as a non-negligible dynamical ingredient. By assuming a bulge, an exponential disk for the stellar and gaseous distributions, and a dark halo and disk magnetic fields, we fit the rotation velocity of the Milky Way. In general, when the magnetic contribution is added to the dynamics, a better description of the rotation curve is obtained. Our main conclusion is that magnetic fields should be taken into account for the Milky Way

Aims. The super-Earth planet GJ 1214b has recently been the focus of several studies, which use the transit spectroscopy technique to determine the nature of its atmosphere. Here, we focus on the Halpha line as a tool to further restrict the nature of GJ 1214b’s atmosphere. Methods. We used the Gran Telescopio Canarias (GTC) OSIRIS instrument to acquire narrow-band photometry with tunable filters. We were able to observe the primary transit of the super-Earth GJ 1214 in three bandpasses: two centered in the continuum around Halpha (653.5 nm and 662.0 nm) and one centered at the line core

The stellar origin of the extremely hydrogen-deficient R Coronae Borealis (RCB) stars has remained a mystery for astronomers since their discovery more than two hundred years ago.  Two competing scenarios are commonly advocated. In the first one, a final helium shell flash occurs on a cooling white dwarf star or a very late thermal pulse is experienced by a post-AGB star. The second scenario involves the merger of two white dwarfs: a carbon–oxygen white dwarf accretes ahelium white dwarf. Evidence from the chemical compositions of RCB stars suggests that most are products of a merger

The effects that interactions produce on galaxy disks and how they modify the subsequent formation of bars need to be distinguished to fully understand the relationship between bars and environment. To this aim we derive the bar fraction in three different environments ranging from the field to Virgo and Coma Clusters, covering an unprecedentedly large range of galaxy luminosities (or, equivalently, stellar masses). We confirm that the fraction of barred galaxies strongly depends on galaxy luminosity. We also show that the difference between the bar fraction distributions as a function of