7 research outputs found
Probing quantum gravity using photons from a flare of the active galactic nucleus Markarian 501 observed by the MAGIC telescope
We analyze the timing of photons observed by the MAGIC telescope during a
flare of the active galactic nucleus Mkn 501 for a possible correlation with
energy, as suggested by some models of quantum gravity (QG), which predict a
vacuum refractive index \simeq 1 + (E/M_{QGn})^n, n = 1,2. Parametrizing the
delay between gamma-rays of different energies as \Delta t =\pm\tau_l E or
\Delta t =\pm\tau_q E^2, we find \tau_l=(0.030\pm0.012) s/GeV at the 2.5-sigma
level, and \tau_q=(3.71\pm2.57)x10^{-6} s/GeV^2, respectively. We use these
results to establish lower limits M_{QG1} > 0.21x10^{18} GeV and M_{QG2} >
0.26x10^{11} GeV at the 95% C.L. Monte Carlo studies confirm the MAGIC
sensitivity to propagation effects at these levels. Thermal plasma effects in
the source are negligible, but we cannot exclude the importance of some other
source effect.Comment: 12 pages, 3 figures, Phys. Lett. B, reflects published versio
Probing quantum gravity using photons from a flare of the active galactic nucleus Markarian 501 observed by the MAGIC telescope
CaracterĂsticas agronĂŽmicas e nutricionais do milho adubado com nitrogĂȘnio, molibdĂȘnio e zinco
Improving the performance of the single-dish Cherenkov telescope MAGIC through the use of signal timing.
The Cherenkov light flashes produced by Extensive Air Showers are very short
in time. A high bandwidth and fast digitizing readout, therefore, can minimize
the influence of the background from the light of the night sky, and improve
the performance in Cherenkov telescopes. The time structure of the Cherenkov
image can further be used in single-dish Cherenkov telescopes as an additional
parameter to reduce the background from unwanted hadronic showers. A
description of an analysis method which makes use of the time information and
the subsequent improvement on the performance of the MAGIC telescope
(especially after the upgrade with an ultra fast 2 GSamples/s digitization
system in February 2007) will be presented. The use of timing information in
the analysis of the new MAGIC data reduces the background by a factor two,
which in turn results in an enhancement of about a factor 1.4 of the flux
sensitivity to point-like sources, as tested on observations of the Crab
Nebula.Comment: 27 pages, 11 figures, accepted by Astroparticle Physic
Probing Quantum Gravity using Photons from a flare of the active galactic nucleus Markarian 501 Observed by the MAGIC telescope
We analyze the timing of photons observed by the MAGIC telescope during a
flare of the active galactic nucleus Mkn 501 for a possible correlation with
energy, as suggested by some models of quantum gravity (QG), which predict a
vacuum refractive index \simeq 1 + (E/M_{QGn})^n, n = 1,2. Parametrizing the
delay between gamma-rays of different energies as \Delta t =\pm\tau_l E or
\Delta t =\pm\tau_q E^2, we find \tau_l=(0.030\pm0.012) s/GeV at the 2.5-sigma
level, and \tau_q=(3.71\pm2.57)x10^{-6} s/GeV^2, respectively. We use these
results to establish lower limits M_{QG1} > 0.21x10^{18} GeV and M_{QG2} >
0.26x10^{11} GeV at the 95% C.L. Monte Carlo studies confirm the MAGIC
sensitivity to propagation effects at these levels. Thermal plasma effects in
the source are negligible, but we cannot exclude the importance of some other
source effect.Comment: 12 pages, 3 figures, Phys. Lett. B, reflects published versio