59 research outputs found
Results of the ARGO-YBJ experiment in detection of gamma rays
Abstract The ARGO-YBJ air shower detector has been in stable data taking for five years at the YangBaJing Cosmic Ray Observatory (Tibet, P.R. China, 4300 m a.s.l.) with a duty cycle > 86% and an energy threshold of a few hundreds of GeV. Besides working in shower mode, the detector used the scaler mode technique, which can reach the minimum threshold of 1 GeV. In this paper a selection of results in gamma ray astronomy will be presented, including those from the study of the diffuse emission from the Galactic plane
Prospects for Gamma-Ray Bursts detection by the Cherenkov Telescope Array
The first Gamma-Ray Burst (GRB) catalog presented by the Fermi-Large Area
Telescope (LAT) collaboration includes 28 GRBs, detected above 100 MeV over the
first three years since the launch of the Fermi mission. However, more than 100
GRBs are expected to be found over a period of six years of data collection
thanks to a new detection algorithm and to the development of a new LAT event
reconstruction, the so-called "Pass 8." Our aim is to provide revised prospects
for GRB alerts in the CTA era in light of these new LAT discoveries. We focus
initially on the possibility of GRB detection with the Large Size Telescopes
(LSTs). Moreover, we investigate the contribution of the Middle Size Telescopes
(MSTs), which are crucial for the search of larger areas on short post trigger
timescales. The study of different spectral components in the prompt and
afterglow phase, and the limits on the Extragalactic background light are
highlighted. Different strategies to repoint part of - or the entire array -
are studied in detail.Comment: In Proceedings of the 34th International Cosmic Ray Conference (ICRC
2015), The Hague, The Netherland
Prospects for Gamma-Ray Bursts detection by the Cherenkov Telescope Array
The first Gamma-Ray Burst (GRB) catalog presented by the Fermi-Large Area
Telescope (LAT) collaboration includes 28 GRBs, detected above 100 MeV over the
first three years since the launch of the Fermi mission. However, more than 100
GRBs are expected to be found over a period of six years of data collection
thanks to a new detection algorithm and to the development of a new LAT event
reconstruction, the so-called "Pass 8." Our aim is to provide revised prospects
for GRB alerts in the CTA era in light of these new LAT discoveries. We focus
initially on the possibility of GRB detection with the Large Size Telescopes
(LSTs). Moreover, we investigate the contribution of the Middle Size Telescopes
(MSTs), which are crucial for the search of larger areas on short post trigger
timescales. The study of different spectral components in the prompt and
afterglow phase, and the limits on the Extragalactic background light are
highlighted. Different strategies to repoint part of - or the entire array -
are studied in detail
Creating a high-resolution picture of Cygnus with the Cherenkov Telescope Array
The Cygnus region hosts one of the most remarkable star-forming regions in
the Milky Way. Indeed, the total mass in molecular gas of the Cygnus X complex
exceeds 10 times the total mass of all other nearby star-forming regions.
Surveys at all wavelengths, from radio to gamma-rays, reveal that Cygnus
contains such a wealth and variety of sources---supernova remnants (SNRs),
pulsars, pulsar wind nebulae (PWNe), H II regions, Wolf-Rayet binaries, OB
associations, microquasars, dense molecular clouds and superbubbles---as to
practically be a galaxy in microcosm. The gamma-ray observations along reveal a
wealth of intriguing sources at energies between 1 GeV and tens of TeV.
However, a complete understanding of the physical phenomena producing this
gamma-ray emission first requires us to disentangle overlapping sources and
reconcile discordant pictures at different energies. This task is made more
challenging by the limited angular resolution of instruments such as the Fermi
Large Area Telescope, ARGO-YBJ, and HAWC and the limited sensitivity and field
of view of current imaging atmospheric Cherenkov telescopes (IACTs). The
Cherenkov Telescope Array (CTA), with its improved angular resolution, large
field of view, and order of magnitude gain in sensitivity over current IACTs,
has the potential to finally create a coherent and well-resolved picture of the
Cygnus region between a few tens of GeV and a hundred TeV. We describe a
proposed strategy to study the Cygnus region using CTA data, which combines a
survey of the whole region at and with deeper observations of two sub-regions that host rich
groups of known gamma-ray sources.Comment: In Proceedings of the 34th International Cosmic Ray Conference
(ICRC2015), The Hague, The Netherlands. All CTA contributions at
arXiv:1508.0589
Creating a high-resolution picture of Cygnus with the Cherenkov Telescope Array
The Cygnus region hosts one of the most remarkable star-forming regions in
the Milky Way. Indeed, the total mass in molecular gas of the Cygnus X complex
exceeds 10 times the total mass of all other nearby star-forming regions.
Surveys at all wavelengths, from radio to gamma-rays, reveal that Cygnus
contains such a wealth and variety of sources---supernova remnants (SNRs),
pulsars, pulsar wind nebulae (PWNe), H II regions, Wolf-Rayet binaries, OB
associations, microquasars, dense molecular clouds and superbubbles---as to
practically be a galaxy in microcosm. The gamma-ray observations along reveal a
wealth of intriguing sources at energies between 1 GeV and tens of TeV.
However, a complete understanding of the physical phenomena producing this
gamma-ray emission first requires us to disentangle overlapping sources and
reconcile discordant pictures at different energies. This task is made more
challenging by the limited angular resolution of instruments such as the Fermi
Large Area Telescope, ARGO-YBJ, and HAWC and the limited sensitivity and field
of view of current imaging atmospheric Cherenkov telescopes (IACTs). The
Cherenkov Telescope Array (CTA), with its improved angular resolution, large
field of view, and order of magnitude gain in sensitivity over current IACTs,
has the potential to finally create a coherent and well-resolved picture of the
Cygnus region between a few tens of GeV and a hundred TeV. We describe a
proposed strategy to study the Cygnus region using CTA data, which combines a
survey of the whole region at and with deeper observations of two sub-regions that host rich
groups of known gamma-ray sources
Strategies for the Follow-up of Gravitational Wave Transients with the Cherenkov Telescope Array
The observation of the electromagnetic counterpart of gravitational-wave (GW)
transient GW170817 demonstrated the potential in extracting astrophysical
information from multimessenger discoveries. The forthcoming deployment of the
first telescopes of the Cherenkov Telescope Array (CTA) observatory will
coincide with Advanced LIGO/Virgo's next observing run, O3, enabling the
monitoring of gamma-ray emission at E > 20 GeV, and thus particle acceleration,
from GW sources. CTA will not be greatly limited by the precision of GW
localization as it will be be capable of rapidly covering the GW error region
with sufficient sensitivity. We examine the current status of GW searches and
their follow-up effort, as well as the status of CTA, in order to identify some
of the general strategies that will enhance CTA's contribution to
multimessenger discoveries.Comment: 10 page
Search for gravitational-lensing signatures in the full third observing run of the LIGO-Virgo network
Gravitational lensing by massive objects along the line of sight to the source causes distortions of gravitational wave-signals; such distortions may reveal information about fundamental physics, cosmology and astrophysics. In this work, we have extended the search for lensing signatures to all binary black hole events from the third observing run of the LIGO--Virgo network. We search for repeated signals from strong lensing by 1) performing targeted searches for subthreshold signals, 2) calculating the degree of overlap amongst the intrinsic parameters and sky location of pairs of signals, 3) comparing the similarities of the spectrograms amongst pairs of signals, and 4) performing dual-signal Bayesian analysis that takes into account selection effects and astrophysical knowledge. We also search for distortions to the gravitational waveform caused by 1) frequency-independent phase shifts in strongly lensed images, and 2) frequency-dependent modulation of the amplitude and phase due to point masses. None of these searches yields significant evidence for lensing. Finally, we use the non-detection of gravitational-wave lensing to constrain the lensing rate based on the latest merger-rate estimates and the fraction of dark matter composed of compact objects
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