Astrophysique à Haute Energie

Studying cosmic ray PeVatrons with ultra-high-energy gamma-rays

Recently completed, the Large High Altitude Air Shower Observatory (LHAASO) is the most sensitive detector exploring the sky in the ultra-high-energy (UHE, > 0.1 PeV) gamma-ray domain. It already detected about a dozen sources, whose spectra extend up to photon energies exceeding 1 PeV. Such photons are produced in interactions between protons of multi-PeV energy with ambient matter. These observations are extremely important because, in order to explain the observed spectrum of Galactic cosmic rays, astrophysical sources capable of accelerating protons beyond 1 PeV must exist.

Studying cosmic ray PeVatrons with ultra-high-energy gamma-rays

Recently completed, the Large High Altitude Air Shower Observatory (LHAASO) is the most sensitive detector exploring the sky in the ultra-high-energy (UHE, > 0.1 PeV) gamma-ray domain. It already detected about a dozen sources, whose spectra extend up to photon energies exceeding 1 PeV. Such photons are produced in interactions between protons of multi-PeV energy with ambient matter. These observations are extremely important because, in order to explain the observed spectrum of Galactic cosmic rays, astrophysical sources capable of accelerating protons beyond 1 PeV must exist.

Studying cosmic ray PeVatrons with ultra-high-energy gamma-rays

Completed in 2021, the Large High Altitude Air Shower Observatory  (LHAASO) is the most sensitive instrument probing the sky in the ultra-high-energy (>0.1 PeV) gamma-ray domain. It already detected about a dozen sources whose spectra extend to PeV energies. Such energetic photons are produced in interactions of multi-PeV cosmic rays with ambient matter. LHAASO sources have been tentatively associated with pulsar wind nebulae, young massive stellar clusters and supernova remnants.

Gamma-ray observations of flaring blazars

Super-massive black holes are known to dwell at the center of galaxies. When accreting matter they are observed from Earth as active galactic nuclei (AGNs). In a minority of AGNs the accretion of matter onto the black-hole is associated with the ejection of a relativistic jet of plasma along the polar axis. 
When the black-hole's jet points right in the direction of the Earth, relativistic effects boost the emission and make these objects among the brightest in the Universe. This peculiar AGNs are called blazars. 

Illustration of the Draper lunar lander that will land on the moon in 2025.
Illustration de l’atterrisseur lunaire de la société Draper qui se posera sur la lune en 2025.

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