Filtern
Volltext vorhanden
- nein (2) (entfernen)
Erscheinungsjahr
- 2019 (2) (entfernen)
Dokumenttyp
Sprache
- Englisch (2)
Gehört zur Bibliographie
- ja (2)
Schlagworte
- gamma rays: galaxies (2) (entfernen)
Institut
The blazar Mrk 501 (z = 0.034) was observed at very-high-energy (VHE, E greater than or similar to 100 GeV) gamma-ray wavelengths during a bright flare on the night of 2014 June 23-24 (MJD 56832) with the H.E.S.S. phase-II array of Cherenkov telescopes. Data taken that night by H.E.S.S. at large zenith angle reveal an exceptional number of gamma-ray photons at multi-TeV energies, with rapid flux variability and an energy coverage extending significantly up to 20 TeV. This data set is used to constrain Lorentz invariance violation (LIV) using two independent channels: a temporal approach considers the possibility of an energy dependence in the arrival time of gamma-rays, whereas a spectral approach considers the possibility of modifications to the interaction of VHE gamma-rays with extragalactic background light (EBL) photons. The non-detection of energy-dependent time delays and the non-observation of deviations between the measured spectrum and that of a supposed power-law intrinsic spectrum with standard EBL attenuation are used independently to derive strong constraints on the energy scale of LIV (E-QG) in the subluminal scenario for linear and quadratic perturbations in the dispersion relation of photons. For the case of linear perturbations, the 95% confidence level limits obtained are E-QG,E-1 > 3.6 x 10(17) GeV using the temporal approach and E-QG,E-1 > 2.6 x 10(19) GeV using the spectral approach. For the case of quadratic perturbations, the limits obtained are E-QG,E-2 > 8.5 x 10(10) GeV using the temporal approach and E-QG,E-2 > 7.8 x 10(11) GeV using the spectral approach.
We report on Cosmic Origin Spectrograph observations of the gamma-ray bright blazar B2 1215+30, collected in 2015 November. These observations allow for the confirmation of the source redshift from the detection of a Lyα emission feature at λ ~ 1374 Å. The emission feature places the source at a redshift of z = 0.1305 ± 0.003, confirming the source's ground-based spectral measurement. The gamma-ray emission of the source is discussed in the context of the source distance, required for the accurate reconstruction of the intrinsic gamma-ray emission taking the absorption by the extragalactic background light into account. The source distance is found to be low enough that the previously reported detection of an exceptional flaring event from B2 1215+30 in 2014 cannot be used to investigate opacity-specific spectral and variability characteristics introduced by possible ultra-high-energy cosmic-ray propagation.