The history of mass loss and chemical enrichment is inscribed on the nebulae surrounding post-AGB stars. Of these objects the most prominent record is the circumnuclear region of the Egg Nebula. We present changes in structure and surface brightness of CRL2688 derived from several pairs of Hubble Space Telescope images taken between 1995.5 and 2009

We describe new radial velocity and X-ray observations of extremely low-mass white dwarfs (ELM WDs, ~0.2 M sun) in the Sloan Digital Sky Survey Data Release 4 and the MMT Hypervelocity Star survey. We identify four new short period binaries, including two merger systems. These observations bring the total number of short period binary systems

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We present a summary of main results from the studies performed in the series of papers The chemical composition of the Orion star forming region. We reinvestigate the chemical composition of B-type stars in the Orion OB1 association by means of state-of-the-art stellar atmosphere codes, atomic models and techniques, and compare the resulting

What is the relevance of major mergers and interactions as triggering mechanisms for active galactic nuclei (AGNs) activity? To answer this long-standing question, we analyze 140 XMM-Newton-selected AGN host galaxies and a matched control sample of 1264 inactive galaxies over z ~ 0.3-1.0 and M * 1011.7 M sun with high-resolution Hubble Space

The helioseismic Global Oscillation at Low Frequency (GOLF) and the Variability of solar Irradiance and Gravity Oscillations (VIRGO) instruments onboard SoHO, have been observing the Sun continuously for the last 14 years. In this preliminary work, we characterize the acoustic modes over the entire p-mode range in both, Doppler velocity and