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Twin peak high frequency quasi-periodic oscillations (HF QPOs) observed in the power spectra of Low Mass X-ray Binaries (LMXBs), with either a black hole or a neutron star, have central frequencies that are typical of the orbital motion time-scale close to the compact object. Thus, twin HF QPOs might carry the fingerprint of physical effects in a strongly curved space-time. We study the azimuth phase \phi(t) for orbital motion in the Schwarzschild metric and calculate the power spectra to check whether they display the features seen in the observed ones. We show that the timing of \phi(t) on non-closed orbits can account for the observed twin peak HF QPOs. The uppermost couple of peaks in frequency has the lower peak that corresponds to the azimuthal frequency \nu_{\phi}, the upper one to \nu_{\phi}+\nu_r. The azimuth phase temporal behavior \phi(t) on a slightly eccentric orbit in the Schwarzschild metric is described by a linear function of slope \nu_{\phi} plus an oscillating term at the relativistic radial frequency \nu_r. We deduce that the twin peak HF QPOs might originate from a frequency modulated (FM) signal driven by the kinematics of orbital motion in a curved space-time., Comment: 5 pages, 3 figures. Accepted for publication in MNRAS Letters

Tidal effects on clumps of material during random non-stationary accretion onto a black hole produce phenomena with distinct temporal characteristics in observed light-curves. During such non-stationary accretion events, the shape of the accreting object evolves in time, and observable quasi-periodic phenomena with variable quasi-periods are produced. A number of characteristic light-curves, obtained with numerical simulations, will be shown. Their relevance to observed phenomena will be briefly discussed., Comment: 3 pages, 8 figures

Recent results from the OPERA experiment reported a neutrino beam traveling faster than light. The experiment measured the neutrino time of flight (TOF) over a baseline from the CERN to the Gran Sasso site. The neutrino beam arrives 60 ns earlier than a light ray would do. Because the result has an enormous impact on science, it might be worth double-checking the time definitions with respect to the non-inertial system in which the neutrino travel time was measured. Potential problems in the OPERA data analysis connected with the definition of the reference frame and time synchronization are emphasized. We aim to investigate the synchronization of non-inertial clocks on Earth by relating this time to the proper time of an inertial observer at Solar System Barycenter(SSB). The Tempo2 software was used to time-stamp events observed on the geoid with respect to the SSB inertial observer time. Neutrino results from OPERA might carry the fingerprint of non-inertial effects. The CERN-Gran Sasso clock synchronization is accomplished by applying corrections that depend on special and general relativistic time dilation effects at the clocks, depending on the position of the clocks in the solar system gravitational well. As a consequence, TOF distributions are centered on values shorter by tens of ns than expected, integrating over a period from April to December, longer if otherwise. It is worth remarking that the OPERA runs have always been carried out from April/May to November. If the analysis by Tempo2 holds for the OPERA experiment, the excellent measurement by the OPERA collaboration will turn into a proof of the General Relativity theory in a weak field approximation. The analysis presented here is falsifiable because it predicts that performing the experiment from January to March/April, the neutrino beam will be detected to arrive 50 ns later than light., Comment: 5 pages, 4 figures, accepted for publication in Astronomy and Astrophysics Letters

Natural laser emission may be produced whenever suitable atomic energy levels become overpopulated. Strong evidence for laser emission exists in astronomical sources such as Eta Carinae, and other luminous stars. However, the evidence is indirect in that the laser lines have not yet been spectrally resolved. The lines are theoretically estimated to be extremely narrow, requiring spectral resolutions very much higher (R approx.= 10**8) than possible with ordinary spectroscopy. Such can be attained with photon-correlation spectroscopy on nanosecond timescales, measuring the autocorrelation function of photon arrival times to obtain the coherence time of light, and thus the spectral linewidth. A particular advantage is the insensitivity to spectral, spatial, and temporal shifts of emission-line components due to local velocities and probable variability of 'hot-spots' in the source. A laboratory experiment has been set up, simulating telescopic observations of cosmic laser emission. Numerically simulated observations estimate how laser emission components within realistic spectral and spatial passbands for various candidate sources carry over to observable statistical functions., Comment: Paper presented at the conference 'High Time Resolution Astrophysics', held in Edinburgh, Scotland, September 2007. To appear in D.Phelan, O.Ryan & A.Shearer, eds.,'The Universe at sub-second timescales', AIP Conf.Proc., in press, 2008 (American Institute of Physics, http://www.aip.org/proceedings). 9 pages, 3 figures, 36 references