  The tera-electronvolt (TeV) light curve of gamma-ray burst (GRB) 221009A
shows an unprecedentedly rapid rise at the beginning epoch. This phenomenon
could be due to the strong absorption of photons and electrons within the
emitting region. As the external shock expands outwards and the radius
increases, the volume of matter also increases, leading to a gradual decrease
in the optical depth for TeV photons. We explore several possibilities for the
physical origin of this peculiar behavior. We calculate the optical depth for
TeV photons due to annihilation with lower energy photons in the external shock
and scattering by electrons produced via cascading of the TeV emission. Even
under aggressive assumptions, we find the optical depths for these processes
are orders of magnitude too small to explain the observed light curve. Other
sources of absorbers, such as electrons in the ejecta or external shock, also
do not yield sufficient optical depths. Therefore, the origin of the early
peculiar TeV light curve remains uncertain.
