We present surface spot maps of the K2V primary star in the pre-cataclysmic variable binary system, V471 Tau. The spot maps show the presence of large high-latitude spots located at the sub-white dwarf longitude region. By tracking the relative movement of spot groups over the course of four nights (eight rotation cycles), we measure the surface

Velocity oscillations in sunspot umbrae have been measured simultaneously in two spectral lines: the photospheric Si I λ10827 line and the chromospheric He I λ10830 multiplet. From the full Stokes inversion of temporal series of spectropolarimetric observations, we retrieved, among other parameters, the line-of-sight velocity temporal variations at

The observations were made on 2003 March 30 with the UVES, at the VLT Kueyen Telescope in Cerro Paranal Observatory (Chile). We used the standard settings in both the red and blue arms of the spectrograph, covering the region from 3100 to 10400{AA}. (1 data file).

Sunspot drawings made by Galileo Galilei in 1612 are used to derive the law of differential rotation at that time. The main interest of the work is during the time of observations, just at the beginning of telescopic observations and some decades before the Maunder Minimum (1645 1715), a period where the sunspots almost disappeared from the solar

The Ca II infrared triplet lines around 8540 Å are good candidates for observing chromospheric magnetism. Model spectra of these lines are obtained by combining a radiation hydrodynamic simulation with a Stokes synthesis code. The simulation shows interesting time-varying behavior of the Stokes V profiles as waves propagate through the formation

We report on a search for gravitational-wave bursts in data from the three LIGO interferometric detectors during their third science run. The search targets sub-second bursts in the frequency range 100-1100 Hz for which no waveform model is assumed and has a sensitivity in terms of the root-sum-square (rss) strain amplitude of hrss ~ 10-20 Hz-1/2