Context. Solar-like oscillations have been observed by Kepler and CoRoT in many solar-type stars, thereby providing a way to probe the stars using asteroseismology. Aims: We provide the mode linewidths and mode heights of the oscillations of various stars as a function of frequency and of effective temperature. Methods: We used a time series of

Magnetic field measurements in the upper chromosphere and above, where the gas-to-magnetic pressure ratio β is lower than unity, are essential for understanding the thermal structure and dynamical activity of the solar atmosphere. Recent developments in the theory and numerical modeling of polarization in spectral lines have suggested that

The O-rich asymptotic giant branch (AGB) stars experience strong mass-loss with efficient dust condensation and they are major sources of dust in the interstellar medium. Alumina dust (Al2O3) is an important dust component in O-rich circumstellar shells and it is expected to be fairly abundant in the winds of the more massive and O-rich AGB stars

During HST Cycle 19, we obtained long-slit spectra using STIS of the planetary nebula NGC 3242 with higher spatial resolution than previously published. The full wavelength range is around 1100-10200Å, covering many nebular lines for determining numerous ionic abundances and electron densities and temperatures. In this work, we first analyze the

On 20 August 2010 an energetic disturbance triggered large-amplitude longitudinal oscillations in a large fraction of a nearby filament. The triggering mechanism appears to be episodic jets connecting the energetic event with the filament threads. We analyzed this periodic motion to characterize the underlying physics of the oscillation as well as

This thesis is focused in the study of the quiet Sun photosphere. In particular, in the high speed magnetized flows that can be observed in the solar surface. These events are distinguishable through the detection of highly distorted Stokes V profiles that trace the presence of magnetic plasma which is moving with very high velocities. We have