G. Zavattini

Discovery of an X-ray afterglow associated with the γ-ray burst of 28 February 1997

Establishing the nature of γ-ray bursts is one of the greatest challenges in high-energy astrophysics. The distribution of these bursts is isotropic across the sky, but inhomogeneous in space, with a deficit of faint bursts. It is currently unknown whether γ-ray bursts are produced in our Galaxy or at cosmological distances. The detection and identification of counterparts at other wavelengths are seen as crucial for resolving the origin of the events. Here we report the detection by the Beppo-SAX satellite of an X-ray ‘afterglow’, associated with the γ-ray burst of 28 February 1997 (GRB970228; ref. 3)—the first such detection for any γ-ray burst. The X-ray transient was found to contain a significant fraction of the total energy of the γ-ray burst and, following the initial detection eight hours after the main burst, faded within a few days with a power-law decay function. The rapid locating of this γ-ray burst instigated a multi-wavelength observational campaign that culminated in the identification of a fading optical transient in a position consistent with the X-ray transient reported here.The invention is a three-piece contact assembly for an electrical connector. The contact assembly is characterized by an inner sleeve (10) captivated between a forward outer sleeve (20) and a rear outer sleeve (30) to eliminate deformation and relative movement between the sleeves of a contact assembly.

New PVLAS results and limits on magnetically induced optical rotation and ellipticity in vacuum

In 2006 the PVLAS collaboration reported the observation of an optical rotation generated in vacuum by a magnetic field. To further check against possible instrumental artifacts, several upgrades to the PVLAS apparatus have been made during the past year. Two data taking runs, at the wavelength of 1064 nm, have been performed in the new configuration with magnetic field strengths of 2.3 and 5 T. The 2.3 T field value was chosen in order to avoid stray fields. The new observations do not show the presence of a rotation signal down to the levels of

YAP-PET: first results of a small animal positron emission tomograph based on YAP:Ce finger crystals

1.2\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}8}\text{ }\text{ }\mathrm{rad}

An integrated PET-SPECT small animal imager: preliminary results

at 5 T and

The PVLAS experiment: measuring vacuum magnetic birefringence and dichroism with a birefringent Fabry–Perot cavity

1.0\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}8}\text{ }\text{ }\mathrm{rad}

Limits on low energy photon-photon scattering from an experiment on magnetic vacuum birefringence

at 2.3 T (at 95% C.L.) with 45 000 passes in the magnetic field zone. In the same conditions no ellipticity signal was detected down to

Spectral Properties of the Prompt X-ray Emission and Afterglow from the Gamma-Ray Burst of 1997 February 28

1.4\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}8}

Use of a YAP:Ce matrix coupled to a position-sensitive photomultiplier for high resolution positron emission tomography

at 2.3 T (at 95% C.L.), whereas at 5 T a signal is still present. The physical nature of this ellipticity as due to an effect depending on

Experimental method to detect the magnetic birefringence of vacuum

{B}^{2}

Measurements of vacuum magnetic birefringence using permanent dipole magnets: the PVLAS experiment

can be excluded by the measurement at 2.3 T. These new results completely exclude the previously published magnetically induced vacuum dichroism results, indicating that they were instrumental artifacts. These new results therefore also exclude the particle interpretation of the previous PVLAS results as due to a spin-zero boson. The background ellipticity at 2.3 T can be used to determine a new limit on the total photon-photon scattering cross section of