21 research outputs found
An Ultrahigh-energy -ray Bubble Powered by a Super PeVatron
We report the detection of a -ray bubble spanning at least 100 in ultra high energy (UHE) up to a few PeV in the direction of the
star-forming region Cygnus X, implying the presence Super PeVatron(s)
accelerating protons to at least 10 PeV. A log-parabola form with the photon
index $\Gamma (E) = (2.71 \pm 0.02) + (0.11 \pm 0.02) \times \log_{10} (E/10 \
{\rm TeV})\gamma\sim 0.5^{\circ}\gamma$-rays are observed with 2 photons at
energies above 1 PeV. The general feature of the bubble, the morphology and the
energy spectrum, are reasonably reproduced by the assumption of a particle
accelerator in the core, continuously injecting protons into the ambient
medium
A tera-electronvolt afterglow from a narrow jet in an extremely bright gamma-ray burst 221009A
Some gamma-ray bursts (GRBs) have an afterglow in the tera-electronvolt (TeV)
band, but the early onset of this afterglow has not been observed. We report
observations with the Large High Altitude Air Shower Observatory of the bright
GRB 221009A, which serendipitously occurred within the instrument field of
view. More than 64,000 photons (above 0.2~TeV) were detected within the first
3000 seconds. The TeV photon flux began several minutes after the GRB trigger,
then rose to a flux peak about 10 seconds later. This was followed by a decay
phase, which became more rapid at after the peak. The
emission can be explained with a relativistic jet model with half-opening angle
, consistent with the core of a structured jet. This
interpretation could explain the high isotropic energy of this GRB.Comment: Online published by Journal Science on June 8, 202
Exploring Lorentz Invariance Violation from Ultra-high-energy Gamma Rays Observed by LHAASO
Recently the LHAASO Collaboration published the detection of 12 ultra-high-energy gamma-ray sources above 100 TeV, with the highest energy photon reaching 1.4 PeV. The first detection of PeV gamma rays from astrophysical sources may provide a very sensitive probe of the effect of the Lorentz invariance violation (LIV), which results in decay of high-energy gamma rays in the superluminal scenario and hence a sharp cutoff of the energy spectrum. Two highest energy sources are studied in this work. No signature of the existence of LIV is found in their energy spectra, and the lower limits on the LIV energy scale are derived. Our results show that the first-order LIV energy scale should be higher than about 10^5 times the Planck scale M_{pl} and that the second-order LIV scale is >10^{-3}M_{pl}. Both limits improve by at least one order of magnitude the previous results
Gamma Ray Astronomy with LHAASO
The aim of LHAASO is the development of an air shower experiment able to monitor with unprecedented sensitivity the gamma ray sky at energies from ~200 GeV to 1 PeV, and at the same time be an instrument able to measure the cosmic ray spectrum, composition and anisotropy in a wide energy range (~1 TeV to 1 EeV). LHAASO, thanks to the large area and the high capability of background rejection, can reach sensitivities to gamma ray fluxes above 30 TeV that are about 100 times higher than that of current instruments, offering the possibility to monitor for the first time the gamma ray sky up to PeV energies and to discover the long sought “Pevatrons”
Construction and On-site Performance of the LHAASO WFCTA Camera
The focal plane camera is the core component of the Wide Field-of-view
Cherenkov/fluorescence Telescope Array (WFCTA) of the Large High-Altitude Air
Shower Observatory (LHAASO). Because of the capability of working under
moonlight without aging, silicon photomultipliers (SiPM) have been proven to be
not only an alternative but also an improvement to conventional photomultiplier
tubes (PMT) in this application. Eighteen SiPM-based cameras with square light
funnels have been built for WFCTA. The telescopes have collected more than 100
million cosmic ray events and preliminary results indicate that these cameras
are capable of working under moonlight. The characteristics of the light
funnels and SiPMs pose challenges (e.g. dynamic range, dark count rate,
assembly techniques). In this paper, we present the design features,
manufacturing techniques and performances of these cameras. Finally, the test
facilities, the test methods and results of SiPMs in the cameras are reported
here.Comment: 45 pages, 21 figures, articl
Energy spectrum of cosmic protons and helium nuclei by a hybrid measurement at 4300 m a.s.l.
The energy spectrum of cosmic Hydrogen and Helium nuclei has been measured below the so-called
“knee” by using a hybrid experiment with a wide field-of-view Cherenkov telescope and the Resistive Plate Chamber
(RPC) array of the ARGO-YBJ experiment at 4300 m above sea level. The Hydrogen and Helium nuclei have been
well separated from other cosmic ray components by using a multi-parameter technique. A highly uniform energy
resolution of about 25% is achieved throughout the whole energy range (100–700 TeV). The observed energy spectrum
is compatible with a single power law with index
γ
=−2.63±0.0