ﻻ يوجد ملخص باللغة العربية
Spontaneous breaking of Lorentz symmetry at energies on the order of the Planck energy or lower is predicted by many quantum gravity theories, implying non-trivial dispersion relations for the photon in vacuum. Consequently, gamma-rays of different energies, emitted simultaneously from astrophysical sources, could accumulate measurable differences in their time of flight until they reach the Earth. Such tests have been carried out in the past using fast variations of gamma-ray flux from pulsars, and more recently from active galactic nuclei and gamma-ray bursts. We present new constraints studying the gamma-ray emission of the galactic Crab Pulsar, recently observed up to TeV energies by the MAGIC collaboration. A profile likelihood analysis of pulsar events reconstructed for energies above 400GeV finds no significant variation in arrival time as their energy increases. Ninety-five percent~CL limits are obtained on the effective Lorentz invariance violating energy scale at the level of $E_{mathrm{QG}_1} > 5.5cdot 10^{17}$GeV ($4.5cdot 10^{17}$GeV) for a linear, and $E_{mathrm{QG}_2} > 5.9cdot 10^{10}$GeV ($5.3cdot 10^{10}$GeV) for a quadratic scenario, for the subluminal and the superluminal cases, respectively. A substantial part of this study is dedicated to calibration of the test statistic, with respect to bias and coverage properties. Moreover, the limits take into account systematic uncertainties, found to worsen the statistical limits by about 36--42%. Our constraints would have resulted much more competitive if the intrinsic pulse shape of the pulsar between 200GeV and 400GeV was understood in sufficient detail and allowed inclusion of events well below 400GeV.
Aims: To investigate the extension of the very-high-energy spectral tail of the Crab pulsar at energies above 400 GeV. Methods: We analyzed $sim$320 hours of good quality data of Crab with the MAGIC telescope, obtained from February 2007 until April
Due to the high energies and long distances involved, astrophysical observations provide a unique opportunity to test possible signatures of Lorentz Invariance Violation (LIV). Superluminal LIV enables the decay of photons at high energy over relativ
Aims: We aim to measure the Crab Nebula gamma-ray spectral energy distribution in the ~100 TeV energy domain and test the validity of existing leptonic emission models at these high energies. Methods: We use the novel very large zenith angle observ
On January 14, 2019, the Major Atmospheric Gamma Imaging Cherenkov telescopes detected GRB 190114C above 0.2 TeV, recording the most energetic photons ever observed from a gamma-ray burst. We use this unique observation to probe an energy dependence
Milagro observations have found bright, diffuse TeV emission concentrated along the galactic plane of the Milky Way. The intensity and spectrum of this emission is difficult to explain with current models where gamma-ray production is dominated by ha