The neutron star X-ray binary Aql X-1 shows quasi-periodic outbursts about once a year. These active states are relatively well covered in optical/infrared and X-ray domains. In contrast, at radio wavelengths the observations are very scarce (IAUC #5112; ATEL #286; ATEL #491). Following the reports of a new outburst of the object (ATEL #1970; ATEL

Most of our knowledge on young stars comes from snapshot observations: spectra and images taken at a single epoch, or at different epochs at different wavelengths. It is, however, known that many of the systems are variable. Variability at optical and near-infrared wavelength is mostly related to the central star itself. Mid-infrared flux changes

RXTE observations of the intermittent accreting millisecond X-ray pulsar HETE J1900.1-2455 (Kaaret et al. 2006 ApJ 638, 963; Galloway et al. 2007 ApJ 654, L73) showed a Type I X-ray burst on April 2 2009 (08:57 UTC). We detect strong burst oscillations during the peak and initial decay of the burst, drifting upwards from 375.5 Hz to 376.5 Hz

Polarized light provides the most reliable source of information at our disposal for diagnosing the physical properties of astrophysical plasmas, including the magnetic fields of the solar atmosphere. The interaction between radiation and hydrogen plus free electrons through Rayleigh and Thomson scattering gives rise to the polarization of the

We present a uniform study of the chemical abundances of 12 elements (Si, Ca, Sc, Ti, V, Cr, Mn, Co, Ni, Na, Mg, and Al) derived from the spectra of 451 stars observed as part of one of the HARPS GTO planet search programs. Sixty eight of these are planet-bearing stars. The main goals of our work are: i) the investigation of possible differences

We have carried out a photometric and spectroscopic survey of bright high-amplitude δ Scuti (HADS) stars. The aim was to detect binarity and multiperiodicity (or both) in order to explore the possibility of combining binary star astrophysics with stellar oscillations. Here, we present the first results for 10, predominantly southern, HADS variables