We present optical, X-ray, high-energy (lap30 GeV) and very high energy (gap100 GeV; VHE) observations of the high-frequency peaked blazar Mrk 421 taken between 2008 May 24 and June 23. A high-energy γ-ray signal was detected by AGILE with √{TS}=4.5 between June 9 and 15, with F(E>100 MeV) = 42+14 -12 × 10-8 photons cm-2 s-1. This flaring state is

The chemical evolution of the Galaxy and the early Universe is a key topic in modern astrophysics. The most metal-poor Galactic halo stars are now frequently used in an attempt to reconstruct the onset of the chemical and dynamical formation processes of the Galaxy. These stars are an easily-accessible local equivalent of the high-redshift Universe

Studying three samples of early-type galaxies, which include approximately 8800 galaxies and cover a relatively ample magnitude range ( ~ 5.5mag), we find that the coefficients as well as the intrinsic dispersion of the Fundamental Plane depend on the width and brightness of the magnitude range within which the galaxies are distributed. We analyse

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We present an analysis of the chemical abundances of the star Tycho G in the direction of the remnant of supernova (SN) 1572, based on Keck high-resolution optical spectra. The stellar parameters of this star are found to be those of a G-type subgiant with T eff = 5900 ± 100 K, log(g/cms2) = 3.85 ± 0.30 dex, and [Fe/H] = -0.05 ± 0.09. This

Following the study already presented in our previous work, based on the Nordic Optical Telescope (NOT) sample, which consists on five clusters of galaxies within the redshift range 0.15$