TESS Superflares and Quasi-Periodic Pulsations on the Active Ultra-Fast Rotator LO Peg

Ultra-fast rotators (UFRs) are recognized as stars with high rotational velocities and are essential for understanding the mechanisms of angular momentum loss and the underlying magnetic dynamo. The active, young, single, main-sequence, K5–8 type UFR LO Peg (v sin i > 65 km s^{-1}) is especially interesting due to the presence of strong magnetic activity, including very large starspot coverage and frequent flaring events. In this research, using high-precision photometry from the NASA Transiting Exoplanet Survey Satellite (TESS), we performed an in-depth investigation of LO Peg. Using observations from 2022 (Sector 55) and 2024 (Sector 82), with cadences of 2 min and 20 s, respectively, we investigated the evolution of starspots and flaring events. From the 2024 observations, we derive a rotational period of 0.4234 ± 0.0013 days, consistent with previously reported values. Using a combined effective baseline of 51.46 days, we performed a rigorous manual identification of flaring events. The high-precision photometry allowed us to detect 146 flaring events with a flare frequency of ~2.84 per day and energies ranging from 10^{32} to 10^{36} erg. The flare frequency is nearly six times higher than previously reported for LO Peg. The most energetic superflare reached a bolometric energy of 1.83 x 10^{36} erg, with a total duration exceeding 4.5 hours and an equivalent duration of ~46.4 minutes. We derived the magnetic field strength associated with this flare to be 319 ± 61 G. Preliminary analysis also suggests that multiple flaring events are associated with Quasi-Periodic Pulsations (QPPs) during the decay phase. Given the observed energy and flare frequency, which are significantly higher than previously reported, this research provides significant constraints on dynamo theory and the magnetic saturation level in ultra-fast rotators.