  Hot Jupiters have been perceived as loners devoid of planetary companions in
close orbital proximity. However, recent discoveries based on space-borne
precise photometry have revealed that at least some fraction of giant planets
coexists with low-mass planets in compact orbital architectures. We report
detecting a 1.446-day transit-like signal in the photometric time series
acquired with the Transiting Exoplanet Survey Satellite (TESS) for the WASP-84
system, which is known to contain a hot Jupiter on a circular 8.5-day orbit.
The planet was validated based on TESS photometry, and its signal was distilled
in radial velocity measurements. The joint analysis of photometric and Doppler
data resulted in a multi-planetary model of the system. With a mass of $15\,
M_{\oplus}$, radius of $2\, R_{\oplus}$, and orbital distance of 0.024 au, the
new planet WASP-84 c was classified as a hot super-Earth with the equilibrium
temperature of 1300 K. A growing number of companions to hot Jupiters indicates
that a non-negligible part of them must have formed under a quiescent scenario
such as disc migration or in-situ formation.
