Ponente
Descripción
On 2 July 2025, the Gamma-ray Burst Monitor (GBM) onboard the Fermi Gamma-ray Space Telescope detected three short-duration MeV transients with overlapping sky locations. These events, named GRB 250702D/B/E (DBE), were triggered within approximately 1-2 hours of one another. Follow-up observations of this unusually long MeV transient (lasting longer than 3 hours) by the Neil Gehrels Swift Observatory and the Nuclear Spectroscopic Telescope Array over a period of 10 days revealed a steep temporal decline in the soft X-rays. These characteristics suggest that DBE may originate from a relativistic jet launched during the tidal disruption of a star by a compact object. We performed a time resolved spectral analysis of DBE during the prompt phase. The spectra are best described by a single power-law, extending from 10 keV to 40 MeV with a possible break at > 50 MeV. From standard MeV gamma-ray transparency arguments, we derive a lower limit on the jet bulk Lorentz factor (Gamma > 10). These constraints place DBE in agreement with four previously reported relativistic tidal disruption events in terms of outburst luminosity and energetics. The MeV spectra disfavor inverse Compton scattering of disk photons, while synchrotron radiation from sub-TeV electrons naturally accounts for the observed emission. Detection of relativistic tidal disruption events in the MeV gamma-rays open new windows for the characterization of their jet properties.
