Magnetospheric Multiscale (MMS) observations during an extended crossing of the Earth's dayside magnetopause show evidence multiple reconnections at boundary. This occurred when Interplanetary Magnetic Field (IMF) was southward and had a significant BY component. Approximately 2 hr after this crossing, Twin Rocket Investigation Cusp Electrodynamics-2 rockets were launched into northern hemisphe...

We study the positivity of first Chern class a rank r Ulrich vector bundle E on smooth n-dimensional variety $X \subseteq \mathbb P^N$. prove that $c_1(E)$ is very positive every subvariety not contained in union lines X. In particular if X covered by lines, then big and $c_1(E)^n \ge r^n$. Moreover we classify bundles with $c_1(E)^2=0$ surfaces or $c_1(E)^3=0$ threefolds (with some exceptions).

We examine the optical emission line properties of Brightest Cluster Galaxies (BCGs) selected from two large, homogeneous datasets. The first is the X-ray selected National Optical Astronomy Observatory Fundamental Plane Survey (NFPS), and the second is the C4 catalogue of optically selected clusters built from the Sloan Digital Sky Survey Data Release 3 (SDSS DR3). Our goal is to better unders...

Steep X-ray spectral slopes, X-ray excesses and preferred spectral energy breaks in the 01-0.3 MeV range are discussed as the possible consequences of the photospheric component of the GRB relativistic outflow, and of pair breakdown in internal shocks leading to comptonization on semirelativistic electrons or MHD waves. We also discuss the X-ray and UV spectra of GRB afterglows occuring in a de...

We study the correlation between a monochromatic signal from annihilating dark matter and its self-interacting cross section. We apply our argument to a complex scalar dark sector, where the pseudo-scalar plays the role of a warm dark matter candidate while the scalar mediates its interaction with the Standard Model. We combine the recent observation of the cluster Abell 3827 for self-interacti...

X-ray emission features have been detected in at least five GRB afterglows. Their detection and properties are of great importance in our understanding of the nature of the GRB progenitor. Moreover, they provide us with an uncollimated source of photons, allowing us to put firm constraints on the total energy produced in GRBs, and therefore on their degree of collimation. I will review the radi...