We have derived a primordial helium abundance of Yp=0.2477+/-0.0029, based on new atomic physics computations of the recombination coefficients of He I and of the collisional excitation of the H I Balmer lines together with observations and photoionization models of metal-poor extragalactic H II regions. The new atomic data increase our previous

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Aims:Magnetic elements are thought to be described by flux tube models, and are well reproduced by MHD simulations. However, these simulations are only partially constrained by observations. We observationally investigate the relationship between G-band bright points and magnetic structures to clarify conditions, which make magnetic structures

Aims:We aim to understand the real nature of the stellar overdensity at southern galactic latitudes in the region of CMa. Methods: We perform a critical re-analysis and discussion of recent results presented in the literature which interpret the CMa overdensity as the signature of an accreting dwarf galaxy or a new substructure within the Galaxy

Phase-resolved medium-resolution VLT spectroscopy of the low-mass X-ray binary GX9+9 has revealed narrow CIII emission lines that move in phase relative to our new estimate of the ephemeris, and show a velocity amplitude of 230 +/- 35 km s-1. We identify the origin of these lines as coming from the surface of the donor star, thereby providing the

As part of a monitoring campaign of quiescent and outbursting low-mass X-ray binaries with the CTIO/SMARTS telescopes and the Faulkes telescopes , we report observations of Aql X-1 and confirm the optical counterpart of the new X-ray outburst (ATel #1216). On 2007 Aug 30 (MJD 54342.26) we performed optical observations of Aql X-1 for 100 sec each