SGR 1806-20 and the gravitational wave detectors EXPLORER and NAUTILUS

The activity of the soft gamma ray repeater SGR 1806-20 is studied in correlation with the EXPLORER and NAUTILUS data, during the year 2004, for gravitational wave (GW) short signal search. Corresponding to the most significant triggers, the bright outburst on October 5th and the giant flare (GF) on December 27th, the associated GW signature is searched. Two methods are employed for processing the data. With the average-modulus algorithm, the presence of short pulses with energy Egw \geq 1.8 x 10^49 erg is excluded with 90% probability, under the hypothesis of isotropic emission. This value is comparable to the upper limits obtained by LIGO regarding similar sources. Using the cross-correlation method, we find a discrepancy from the null-hypothesis of the order of 1%. This statistical excess is not sufficient to claim a systematic association between the gravitational and the electromagnetic radiations, because the estimated GW upper limits are yet several orders of magnitude far away from the theoretically predicted levels, at least three for the most powerful SGR flare.Comment: Accepted by Physical Review

Upper Limits in the Case That Zero Events are Observed: An Intuitive Solution to the Background Dependence Puzzle

We compare the ``unified approach'' for the estimation of upper limits with an approach based on the Bayes theory, in the special case that no events are observed. The ``unified approach'' predicts, in this case, an upper limit that decreases with the increase in the expected level of background. This seems absurd. On the other hand, the Bayesian approach leads to a result which is background independent. An explanation of the Bayesian result is presented, together with suggested reasons for the paradoxical result of the ``unified approach''.Comment: Latex file (compiled with cernrep.cls included) 5 pages, no figures. To appear in the Proceed. of the workshop on ''Confidence limits'' (CERN, Jan 2000). This paper and related papers also available at http://grwav3.roma1.infn.it

Energy spectrums for proton /200 eV + or = E + or = 1 MeV/ intensities in the outer radiation zone

Energy spectrums for proton intensities in outer radiation zon

Note on the Electron Energy Spectrum in the Inner Van Allen Belt

Electron energy spectrum in the inner van allen bel

Measuring Propagation Speed of Coulomb Fields

The problem of gravity propagation has been subject of discussion for quite a long time: Newton, Laplace and, in relatively more modern times, Eddington pointed out that, if gravity propagated with finite velocity, planets motion around the sun would become unstable due to a torque originating from time lag of the gravitational interactions. Such an odd behavior can be found also in electromagnetism, when one computes the propagation of the electric fields generated by a set of uniformly moving charges. As a matter of fact the Li\'enard-Weichert retarded potential leads to a formula indistinguishable from the one obtained assuming that the electric field propagates with infinite velocity. Feyman explanation for this apparent paradox was based on the fact that uniform motions last indefinitely. To verify such an explanation, we performed an experiment to measure the time/space evolution of the electric field generated by an uniformely moving electron beam. The results we obtain on such a finite lifetime kinematical state seem compatible with an electric field rigidly carried by the beam itself.Comment: 23 pages, 15 figure

IC 5181: An S0 Galaxy with Ionized Gas on Polar Orbits

The nearby S0 galaxy IC 5181 is studied to address the origin of the ionized gas component that orbits the galaxy on polar orbit. We perform detailed photometric and spectroscopic observations measuring the surface brightness distribution of the stars (I-band), ionized gas of IC 5181 (H-alpha narrow band), the ionized-gas and stellar kinematics along both the major and minor axis, and the corresponding line strengths of the Lick indices. We conclude that the galaxy hosts a geometrically and kinematically decoupled component of ionized gas. It is elongated along the galaxy minor axis and in orthogonal rotation with respect to the galaxy disk. The result is suggesting that the gas component is not related to the stars having an external origin. The gas was accreted by IC 5181 on polar orbits from the surrounding environment.Comment: 4 pages, 5 figures, To appear in ASP Conf. Ser., Multi-Spin Galaxies, E. Iodice and E. M. Corsini (eds.