No abstract

Some gamma-ray bursts (GRBs) have a tera–electron volt (TeV) afterglow, but the early onset of this 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 >0.2 TeV were detected within the first 3000 seconds. The TeV flux began several minutes after the GRB trigger, then rose to a peak about 10 seconds later. This was followed by a decay phase, which became more rapid ~650 seconds after the peak. We interpret the emission using a model of a relativistic jet with half-opening angle ~0.8°. This is consistent with the core of a structured jet and could explain the high isotropic energy of this GRB.

No abstract

No abstract

Laser-induced periodic nanotextures (ripples) on Al2O3/TiC ceramic formed by femtosecond laser pulses were investigated. Pulse energy, scanning speed and the number of overscans were studied for the formation of ripples. The evolution of surface morphology, surface roughness and ablation depth with different parameters was measured by scanning electron microscopy, white lighting interferometer and atomic force microscopy. The experimental results indicate that the nanotextures are dependent on the pulse energy and scanning speed, and the optimum parameter for the formation of continuous and clear ripples is 1.75 μJ with 500 μm s−1 or 2 μJ with 500 μm s−1. Finally, the mechanism of the formation of laser-induced periodic surface nanotextures on Al2O3/TiC ceramic surface was discussed.