6 papers
A self-consistent explanation of the MeV line in GRB 221009A unveils a dense circum-stellar medium
O. S. Salafia, A. Celotti, E. Sobacchi +6
GRB~221009A has been the brightest gamma-ray burst (GRB) observed to date, and its afterglow has been characterized with unprecedented detail at TeV energies by LHAASO. Quite puzzl…
MeV absorption in gamma-ray bursts as a probe of their progenitor environments
Gor Oganesyan, Om Sharan Salafia, Emanuele Sobacchi +8
A small fraction of X-ray photons from -ray bursts (GRBs), after escaping the relativistic jet, are scattered by electrons in the circumburst medium. Subsequent photon-photon a…
Temporal variability of polarization in blazars
Filippo Bolis, Emanuele Sobacchi, Fabrizio Tavecchio
We investigate the temporal variability of polarization of synchrotron radiation from blazar jets. Multiwavelength observations revealed high-amplitude rotations of the electric ve…
Ultra-long MeV transient from a relativistic jet: a tidal disruption event candidate
Gor Oganesyan, Elias Kammoun, Annarita Ierardi +11
On July 2, 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 ev…
Filamentation of the electromagnetic precursor in relativistic quasi-perpendicular electron-positron shocks
Emanuele Sobacchi, Yuri Lyubarsky, Lorenzo Sironi +1
We present a scenario that could explain non-thermal particle acceleration in relativistic quasi-perpendicular electron-positron shocks, such as the termination shock of pulsar win…
Do multifrequency polarimetric observations of BL Lac rule out a hadronic origin for its X-ray emission?
F. Tavecchio, F. Bolis, E. Sobacchi +2
Recent multifrequency polarimetric observations of the eponymous blazar BL Lac reveal an extremely large degree of polarization in the optical band (average of , reaching $45…