696 research outputs found
Observations of Extragalactic Sources with the MAGIC Telescope
MAGIC is currently the world's largest single dish ground based imaging
atmospheric Cherenkov telescope. During the first year of operation, more than
20 extragalactic sources have been observed and several of them detected. Here
we present results of analyzed data, including discussion about spectral and
temporal properties of the detected sources. In addition, we discuss
implications of the measured energy spectra of distant sources for our
knowledge of the extragalactic background light.Comment: to appear in proceedings of Multi Messenger conference, Barcelona,
July 4-7, 200
Axion-like particle imprint in cosmological very-high-energy sources
Discoveries of very high energy (VHE) photons from distant blazars suggest
that, after correction by extragalactic background light (EBL) absorption,
there is a flatness or even a turn-up in their spectra at the highest energies
that cannot be easily explained by the standard framework. Here, it is shown
that a possible solution to this problem is achieved by assuming the existence
of axion-like particles (ALPs) with masses ~1 neV. The ALP scenario is tested
making use of observations of the highest redshift blazars known in the VHE
energy regime, namely 3C 279, 3C 66A, PKS 1222+216 and PG 1553+113. In all
cases, better fits to the observed spectra are found when including ALPs rather
than considering EBL only. Interestingly, quite similar critical energies for
photon/ALP conversions are also derived, independently of the source
considered.Comment: 12 pages, 2 figures, 2 tables; accepted by JCAP. Replaced to match
the accepted versio
Upgrade of the MAGIC Telescope with a Multiplexed Fiber-Optic 2 GSamples/s FADC Data Acquisition system
In February 2007 the MAGIC Air Cherenkov Telescope for gamma ray astronomy
was fully upgraded with a fast 2 GSamples/s digitization system. The upgraded
readout system uses a novel fiber-optic multiplexing technique. It consists of
10-bit 2 GSamples/s FADCs to digitize 16 channels consecutively and optical
fibers to delay the analog signals. A distributed data acquisition system using
GBit Ethernet and FiberChannel technology allows to read out the 100 kByte
events with a continuous rate of up to 1 kHz.Comment: 4 pages, 6 figures, to appear in the proceedings of the 30th
International Cosmic Ray Conference, Merida, July 200
Dark Matter signals from Draco and Willman 1: Prospects for MAGIC II and CTA
The next generation of ground-based Imaging Air Cherenkov Telescopes (IACTs)
will play an important role in indirect dark matter searches. In this article,
we consider two particularly promising candidate sources for dark matter
annihilation signals, the nearby dwarf galaxies Draco and Willman 1, and study
the prospects of detecting such a signal for the soon-operating MAGIC II
telescope system as well as for the planned installation of CTA, taking special
care of describing the experimental features that affect the detectional
prospects. For the first time in such a study, we fully take into account the
effect of internal bremsstrahlung, which has recently been shown to
considerably enhance, in some cases, the gamma-ray flux at the high energies
where Atmospheric Cherenkov Telescopes operate, thus leading to significantly
harder annihilation spectra than traditionally considered. While the detection
of the spectral features introduced by internal bremsstrahlung would constitute
a smoking gun signature for dark matter annihilation, we find that for most
models the overall flux still remains at a level that will be challenging to
detect unless one adopts rather (though by no means overly) optimistic
astrophysical assumptions about the distribution of dark matter in the dwarfs.Comment: 10 pages, 4 figures, minor changes, matches the published version
(JCAP
Sensitivity for tau neutrinos at PeV energies and beyond with the MAGIC telescopes
The MAGIC telescopes, located at the Roque de los Muchachos Observatory (2200
a.s.l.) in the Canary Island of La Palma, are placed on the top of a mountain,
from where a window of visibility of about 5 deg in zenith and 80 deg in
azimuth is open in the direction of the surrounding ocean. This permits to
search for a signature of particle showers induced by earth-skimming cosmic tau
neutrinos in the PeV to EeV energy range arising from the ocean. We have
studied the response of MAGIC to such events, employing Monte Carlo simulations
of upward-going tau neutrino showers. The analysis of the shower images shows
that air showers induced by tau neutrinos can be discriminated from the
hadronic background coming from a similar direction. We have calculated the
point source acceptance and the expected event rates, assuming an incoming tau
neutrino flux consistent with IceCube measurements, and for a sample of generic
neutrino fluxes from photo-hadronic interactions in AGNs. The analysis of about
30 hours of data taken toward the sea leads to a point source sensitivity for
tau neutrinos at the level of the down-going point source analysis of the
Pierre Auger Observatory.Comment: Proceedings of the 35th International Cosmic Ray Conference (ICRC
2017), Bexco, Busan, Korea,(arXiv:1708.05153
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