  We study the properties of the type-C quasi-periodic oscillation (type-C QPO)
of MAXI J1348-630 during its 2019 outburst and reflare with NICER. This is the
first time that the evolution of the properties of type-C QPOs is studied
during an outburst reflare. We found that the properties of the type-C QPO
during the reflare are similar to those of type-C QPOs observed in other
black-hole systems during outburst. This suggests that the physical processes
responsible for type-C QPOs are the same in a reflare and in an outburst. We
also found that the FWHM of a high-frequency broadband component observed
during the reflare changes significantly with energy. We studied the
energy-dependent fractional rms amplitude and phase lags of the type-C QPO from
0.5 keV to 12 keV. We found that the fractional rms amplitude increases up to
2-3 keV and then remains approximately constant above this energy, and the lag
spectra of the type-C QPO are hard. We discuss the dependence of the fractional
rms amplitude and phase lags with energy in the context of Comptonisation as
the radiative mechanism driving the QPO rms and lag spectra.
