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Showing 1–8 of 8 results
Advanced filters: Author: G. Barbiellini Clear advanced filters

  • Super-massive black holes in active galaxies can accelerate particles to relativistic energies, producing jets with associated γ-ray emission. Galactic 'microquasars' also produce relativistic jets; however, apart from an isolated event detected in Cygnus X-1, there has hitherto been no systematic evidence for the acceleration of particles to gigaelectronvolt or higher energies in a microquasar. Here, a report of four γ-ray flares with energies above 100 MeV from the microquasar Cygnus X-3 illuminates this important problem.

    • M. Tavani
    • A. Bulgarelli
    • L. Salotti
    Research
    Nature
    Volume: 462, P: 620-623

  • In April 2020, the AGILE satellite registered an X-ray burst temporally coincident with a radio burst from the Galactic magnetar SGR 1935+2154. As seen in hard X-rays, the burst was cut off above 80 keV and had an isotropically emitted energy of about 1040 erg.

    • M. Tavani
    • C. Casentini
    • F. D’Amico
    Research
    Nature Astronomy
    Volume: 5, P: 401-407

  • A multi-frequency observing campaign of the γ-ray burst GRB 190114C reveals a broadband double-peaked spectral energy distribution, and the teraelectronvolt emission could be attributed to inverse Compton scattering.

    • V. A. Acciari
    • S. Ansoldi
    • D. R. Young
    Research
    Nature
    Volume: 575, P: 459-463

  • Electrical readout of the state of an antiferromagnet is an important goal for spintronic applications. Now, detection of the electrical voltage created by a thermal gradient in a canted antiferromagnet suggests a route for achieving this goal.

    • Weiwei Lin
    • Jiaming He
    • C. L. Chien
    Research
    Nature Physics
    Volume: 18, P: 800-805

  • Lorentz invariance — the postulate that all observers measure exactly the same speed of light in vacuum, independent of photon energy — is a cornerstone of Einstein's special relativity, but it has been suggested that it might break near the Planck scale. A possible variation of photon speed with energy is a key test for this proposed violation; here, by studying sharp features in γ-ray burst light-curves to look for even tiny variations in photon speed, no evidence for the violation of Lorentz invariance is found.

    • A. A. Abdo
    • M. Ackermann
    • M. Ziegler
    Research
    Nature
    Volume: 462, P: 331-334

  • Gigaelectronvolt emission from a magnetar giant flare is discovered by the Fermi Gamma-ray Space Telescope, between 19 s and 284 s after the initial detection of a signal in the megaelectronvolt energy band, potentially generated by an ultra-relativistic outflow far from the stellar magnetosphere.

    • M. Ajello
    • W. B. Atwood
    • G. Zaharijas
    Research
    Nature Astronomy
    Volume: 5, P: 385-391

  • It is widely accepted that strong and variable radiation detected over all accessible energy bands in a number of active galaxies arises from a relativistic, Doppler-boosted jet pointing close to our line of sight. However, the size of the emitting zone and the location of this region relative to the central supermassive black hole are poorly understood. Here, the coincidence of a γ-ray flare with a dramatic change of optical polarization angle is reported, providing evidence for co-spatiality of optical and γ-ray emission regions and indicating a highly ordered jet magnetic field.

    • A. A. Abdo
    • M. Ackermann
    • M. Sikora
    Research
    Nature
    Volume: 463, P: 919-923