We are all familiar with the fact that a linear flow of water in a tube can be obtained only for velocities below a certain critical limit and that, when the velocity exceeds this limit, laminar flow ceases and a complex, irregular, and fluctuating motion sets in. More generally than in this context of flow through a tube, it is known that motions

The MAGIC telescope took data of very high energy γ-ray emission from the blazar Markarian 421 (Mrk 421) between 2004 November and 2005 April. We present a combined analysis of data samples recorded under different observational conditions, down to γ-ray energies of 100 GeV. The flux was found to vary between 0.5 and 2 crab (integrated above 200

We report the discovery of a previously unseen X-ray point source detected in a 5ks observation starting on 2007-07-05.54 UT as part of our ongoing Chandra/HST M31 transient program. The source was detected on the edge of ACIS-S at coordinates RA(J2000) 00:40:59.2, Dec(J2000) +41:15:51.2, with centroid position errors of 2.4" and 3.0", respectively

A comparison between linear-stability analysis and observations of pulsation modes in five δ Scuti stars, belonging to the same cluster, is presented. The study is based on a work by Michel et al., in which such a comparison was performed for a representative set of model solutions obtained independently for each individual star considered. In this

Since the beginning of its operation in April 2005, the MAGIC telescope was able to observe ten different GRB events since their early beginning, even while the prompt emission was still ongoing. Observations, with energy thresholds spanning between 80 and 300 GeV, did not reveal any γ-ray emission. We present a direct determination of the MAGIC

Aims:We study the structure of the magnetic field vector in the internetwork and search for the presence of small-scale loops. Methods: We invert 1.56 μm spectropolarimetric observations of internetwork regions at disc centre by applying the SIR code. This allows us to recover the atmospheric parameters that play a role in the formation of these