tokens: individual star. Tables 5 and 6 list the top 20 stars sorted by flare frequency f * and the number of flares N *flares , respectively. TIC43472154 is the most active star with an impressive flare frequency. If it is not coincidentally observed at an extraordinary active period, TIC43472154 can generate 233.17 flares per year. Besides, this star is not accompanied by any fainter stars or M dwarfs, according to the cross-match results from Gaia and Hipparcos data. This occurrence rate is much higher than that of KIC10422252, which is 41.6 flares per year (Shibayama et al. 2013 ). Figure 7 plots the light curve of TIC43472154. Superflares are marked with downward arrows. Figure 7. Light curve of TIC43472154. Small arrows mark those superflares selected from automatic software, and checked through a pixel-level pattern. Table 5 Stellar Properties of Flare Stars Sorted by Star Activity f * Note. Top 20 flare stars sorted by flare frequency ( f * ). The headers of this table are the same as in Table 1 . Table 6 Stellar Properties of Flare Stars Sorted by Number of Flares Note. Top 20 flare stars sorted by the number of flares on the corresponding star. The headers of this table are the same as in Table 5 . Another target, TIC364588501, was observed by all sectors of TESS and exhibits the largest number of flares (63). Additionally, like TIC43472154, this star is also a single star, according to the cross-match results from Gaia and Hipparcos data. TIC364588501 became more active than usual in the last 15 days of sector 5, and generated 15 superflares (Figure 8 ). Figure 8. Same as Figure 7 , but for TIC364588501. The most energetic superflare comes from TIC93277807, releasing 1.77 × 10 37 erg in around 1.5 hr. This value consists with the inference that energy releasing through a stellar flare is saturated at ∼2 × 10 37 erg (Wu et al. 2015 ). 3.4. Planets of Flare Stars Hot Jupiters are considered as one of the essential factors that can produce superflares on host stars (e.g., Rubenstein Schaefer 2000 ; Ip et al. 2004 ). According to these studies, it is not possible for the Sun to generate superflares. However, a lot of statistical works based on Kepler data did not detect hot Jupiters around flare stars (Maehara et al. 2012 ; Shibayama et al. 2013 ; Maehara et al. 2015 ). We made a cross-check between our 400 flare stars with the Exoplanet Follow-up Observing Program for TESS (ExoFOP– TESS 3 3 https://exofop.ipac.caltech.edu/tess/ ). Cross-matching results are listed in Table 7 . There are four stars (TIC25078924, 44797824, 257605131, and 373844472) that have planet candidates. These four stars are unlikely to affect our statistical results. We thus did not exclude them in the analysis. Besides, there is only one star (TIC410214986) that possesses a confirmed hot planet (Newton et al. 2019 ). This is an interesting planet, and we list its parameters in Table 7 , even if its hosting star (TIC410214986) is flagged as a binary system from the
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