Exploring Gamma-Ray Bursts with Konus-Wind and Beyond: Population Properties, Classification, and Probes of Fundamental Physics.

Gamma-ray bursts (GRBs) are among the most powerful and luminous transient phenomena in the Universe, detectable up to redshifts of z~9.4. Their prompt emission, consisting of gamma-ray flashes lasting from less than a second to thousands of seconds, most probably originates from relativistic ejecta launched by a central engine, such as a newborn black hole or magnetar. The detection of a short GRB 170817A in coincidence with the gravitational-wave signal from a binary neutron star merger further established GRBs as important sources for multimessenger astrophysics.

In this talk, I will present studies of GRB populations, prompt emission, classification, and application of GRBs to fundamental physics. I will first discuss the GRB population detected in the Konus-Wind experiment operated by the Ioffe institute since 1994, including the catalog of bursts with measured redshifts and its extension to weak bursts jointly detected with Swift/BAT. These samples enable broad-band studies of GRB spectral parameters, durations, energetics, and luminosities, revealing a discrepancy in the GRB formation rate and cosmic star-formation history. To investigate whether this discrepancy may be related to GRB classification, I will present recent work on GRB taxonomy in the cosmological rest frame, testing whether the traditional short/long dichotomy points to a third population when redshift effects are properly accounted for. I will also present a spectral analysis of GRBs simultaneously observed by Konus-Wind and BeppoSAX/WFC, testing the consistency of their prompt emission with synchrotron radiation. Finally, I will discuss the use of GRBs to probe possible violations of Lorentz invariance.