M31 has been monitored by a Chandra GTO program, which used both the HRC and ACIS from 1999 to 2001 and a GO program, which used ACIS-S during 2000-2001. We report here the lightcurves of X-ray sources in M31 during the past two years. X-ray sources in M31, like in our Galaxy, exhibit variability on long timescales (days to months). Some sources

We present K-band photometry and low-resolution near-infrared spectroscopy from 1.44 to 2.45 μm of isolated planetary-mass candidate members in the σ Orionis cluster found by Zapatero Osorio et al. The new data have been obtained with NIRC at the Keck I telescope. All of our targets, except for one, are confirmed as likely cluster members. Hence

Coded Aperture System performances are defined by the geometry of the code, detector pixel geometry relationship and focal length. Physical Coded Aperture Systems deviate from the ideal ones on two basic aspects: uncertainties on pixel location and size coming form the manufacturing process and deviations from their theoretical transparency/opacity

We derive some element abundances for the central star of the planetary nebula K648 from analysis of Hubble Space Telescope Faint Object Spectrograph spectra (1200-3300 Å). Carbon is found to be approximately 4 times overabundant with respect to solar values, while oxygen is underabundant and silicon about solar, and He/H=0.6. The stellar continuum

The selection from available commercial market of a set of slides to be used in an habitable pressurised module in space, to draw a 660 mm box out of a rack, up to a completely extracted position in a safely supported configuration, seems in principle not to be a complicated task. That was the first approach taken in the design process of the

We report in this paper on the design and progress of the ESO Laser Guide Star Facility. The project will create a user facility embedded in UT4, to produce in the Earth's mesosphere laser guide stars, which extend the sky coverage of adaptive optics systems on the VLT UT4 telescope. Embedded into the project are provisions for multiple LGS to cope