Description
The physical mechanism powering the prompt emission of gamma-ray bursts (GRBs) —internal
shocks, magnetic reconnection, or photospheric dissipation —is one of the longest-standing open
questions in high-energy astrophysics. While gamma-ray observations alone cannot break the
model degeneracy, simultaneous optical monitoring at sub-second cadence offers a powerful and
largely unexploited discriminant: the temporal correlation (or lack thereof) between optical and
gamma-ray pulses directly constrains the emission radius, the magnetization of the outflow, and
the presence of a reverse shock. We argue that the Italian astronomical community is uniquely
positioned to contribute to this field. On one hand, wide-field high-cadence imagers (analogous
to TORTORA or the proposed Mezzocielo concept) can serendipitously catch the prompt phase
without any slew delay, at the cost of shallow limiting magnitude. On the other hand, SIFAPclass
photon-counting instruments on medium-to-large aperture telescopes, if paired with a fastresponse
alert system, can reach the field of long-duration GRBs (T90 > 90 s) and ultra-long GRBs
(T90 > 1000 s) while the prompt phase is still ongoing, providing photon-by-photon light curves
with millisecond resolution. We quantify the expected detection rates under conservative assumptions,
discuss the minimum resolvable timescales as a function of telescope aperture and GRB
brightness, and outline a realistic observational strategy to maximize the scientific yield of each
event. A single well-observed prompt optical light curve, obtained simultaneously with Swift/BAT
or Fermi/GBM data, would provide diagnostics unavailable by any other means.