  Superbursts are long duration, rare, and extremely energetic thermonuclear
explosions of neutron star low-mass X-ray binaries (NS LMXBs), which are
proposed to be due to unstable carbon ignition. We report the superburst
properties and consequences from Aql X-1 observed by the Neutron Star Interior
Composition Explorer (NICER), the Monitor of All-sky X-ray Image, Swift, and
Insight Hard X-ray Modulation Telescope (Insight-HXMT) on the MJD 59130.7. We
found two faint type I X-ray bursts 9.44 days after the superburst with a short
recurrence time of 7.6 minutes, which is the most accurate measurement of the
quenching time in all NS LMXBs with observed superbursts. We also discovered
mHz quasi-periodic oscillations in the frequency range 2.7--11.3 mHz
immediately after the superburst, before and after the resumption of the first
type I X-ray burst from NICER, Swift, and Insight-HXMT observations. For the
first time, we observed the transition from superburst, via marginally stable
burning to unstable burning in NS LMXBs. We compared the quenching time and the
recurrence time of type I X-ray bursts with simulations.

High Energy Astrophysical Phenomena