A new method of calculating microlensing magnification patterns is proposed that is based on the properties of the backward gravitational lens mapping of a lattice of polygonal cells defined at the image plane. To a first-order approximation, the local linearity of the transformation allows us to compute the contribution of each image-plane cell to

Aims.We investigate the effects of varying the magnetic field strength and the twist of a flux tube as it rises through the solar interior and emerges into the atmosphere. Methods: .Using a 3D numerical MHD code, we consider a simple stratified model, comprising of one solar interior layer and three overlying atmospheric layers. We set a horizontal

Optical novae have recently been identified as the major class of supersoft X-ray sources in M 31 based on ROSAT and early XMM-Newton and Chandra observations. This paper reports on a search for X-ray counterparts of optical novae in M 31 based on archival Chandra HRC-I and ACIS-I as well as XMM-Newton observations of the galaxy center region

We present the results of the DART imaging and CaII triplet (CaT) survey of the Fornax dwarf spheroidal galaxy (dSph) at ESO. We collected hundreds of low resolution spectra of Red Giant Branch (RGB) stars in the CaT region, using VLT/FLAMES in Medusa mode, with the GIRAFFE spectrograph (grating LR8, resolving power R~6500). We list the results for

A series of missions will be launched over the next few decades that will be designed to detect and characterize extrasolar planets around nearby stars. These missions will search for habitable environments and signs of life (biosignatures) in planetary spectra. The vegetation's ``red edge,'' an enhancement in the Earth's spectrum near 700 nm when

We selected a large sample of O-B stars that were considered as (candidate) slowly pulsating B, beta Cep, and Maia stars after the analysis of their Hipparcos data. We analysed both the Hipparcos data and our new seven passband Geneva data collected for these stars during the first three years of scientific operations of the Mercator telescope. We