2020/05/31 by S. Mereghetti, V. Savchenko, C. Ferrigno +23 · 3 citations
Physics and Astronomy · #astro-ph.HE
paper · pdf · doi:10.3847/2041-8213/aba2cf
Accepted for publication on The Astrophysical Journal Letters - revised accepted version
arxiv created 2020/07/05 · arxiv updated 2020/08/05
We report on INTEGRAL observations of the soft γ-ray repeater SGR 1935+2154 performed between 2020 April 28 and May 3. Several short bursts with fluence of ∼10-7-10-6 erg cm-2 were detected by the IBIS instrument in the 20-200 keV range. The burst with the hardest spectrum, discovered and localized in real time by the INTEGRAL Burst Alert System, was spatially and temporally coincident with a short and very bright radio burst detected by the CHIME and STARE2 radio telescopes at 400-800 MHz and 1.4 GHz, respectively. Its lightcurve shows three narrow peaks separated by ∼29 ms time intervals, superimposed on a broad pulse lasting ∼0.6 s. The brightest peak had a delay of 6.5±1.0 ms with respect to the 1.4 GHz radio pulse (that coincides with the second and brightest component seen at lower frequencies). The burst spectrum, an exponentially cut-off power law with photon index Γ=0.7-0.2+0.4 and peak energy Ep=65±5 keV, is harder than those of the bursts usually observed from this and other magnetars. By the analysis of an expanding dust scattering ring seen in X-rays with the \it Neil Gehrels Swift Observatory XRT instrument, we derived a distance of 4.4-1.3+2.8 kpc for SGR 1935+2154, independent of its possible association with the supernova remnant G57.2+0.8. At this distance, the burst 20-200 keV fluence of (6.1± 0.3)×10-7 erg cm-2 corresponds to an isotropic emitted energy of ∼1.4×1039 erg. This is the first burst with a radio counterpart observed from a soft γ-ray repeater and it strongly supports models based on magnetars that have been proposed for extragalactic fast radio bursts.