We report on 3 Chandra ACIS-I observations containing the two M31 transient X-ray sources announced by Haberl et al. (2006, ATel #881) and followed up by Pietsch et al. (2006, ATel #899). These observations are part of our ongoing Chandra/HST M31 transient program XMMU J004215.8+411924: This High Mass X-ray Binary was first observed with Chandra

We present the results from an X-ray and optical survey of a sample of radio jets in AGN with Chandra and HST. We focus on the first six sources observed at X-rays, in four of which a bright X-ray jet was detected for the first time. In three out of four cases optical emission from the jet is also detected in the HST images. We compare the X-ray

As part of our Guaranteed Time Observer program on the Chandra X-Ray Observatory, we have an M31 observing program which has two major objectives. First to monitor the galaxy on a monthly basis to detect transient sources and follow their evolution. Second to obtain a deep image of the central region of M31 in order to measure the luminosity

One of the intents of the ground-based gamma-ray astronomy is to obtain a sky survey in the TeV energy region, and nowadays this target can be reached with giant arrays of telescopes, which however need many pointings due to their small field of view. A different approach is on the basis of GAW, acronym for Gamma Air Watch, an array of three

We contribute to the subject of the physical interpretation of exact solutions by characterizing them through a systematic study in terms of unambiguous physical concepts coming from systems in linearized gravity. We use the physical meaning of the leading order behavior of the Weyl spinor components $Psi_0^0$, $Psi_1^0$ and $Psi_2^0$ and of the

The calculation of solar absolute fluxes in the near-UV is revisited, discussing in some detail recent updates in theoretical calculations of bound free opacity from metals. Modest changes in the abundances of elements such as Mg and iron-peak elements have a significant impact on atmospheric structure, and therefore self-consistent calculations