Tsinghua University-Ma Huateng Telescopes for Survey (TMTS) aims to detect fast-evolving transients in the Universe, which has led to discovery of thousands of short period variables and eclipsing binaries since 2020. In this paper, we present the observed properties of 125 flare stars identified by the TMTS within the first two years, with an attempt to constrain their eruption physics. As expected, most of these flares were recorded in late-type red stars with G_BP_-G_RP_>2.0mag, however, the flares associated with blue stars of them tend to be on average more energetic and have broader profiles. The peak flux (F_peak_) of the flare is found to depend strongly on the equivalent duration (ED) of the energy release, i.e., F_peak_{pro.to}ED^0.72+/-0.04^, which is consistent with the results derived from the Kepler and Evryscope samples. This relation is likely related to the magnetic loop emission, while for the more popular non-thermal electron heating model a specific time evolution may be required to generate this relation. We notice that flares produced by hotter stars have a flatter F_peak_{pro.to}ED relation compared to that from cooler stars, which is related to the statistical discrepancy in light-curve shape of flare events with different colors. With the spectra from the LAMOST, we found that flare stars have apparently stronger H{alpha} emission than inactive stars, especially at low temperature end, suggesting that chromospheric activity plays an important role in producing flares. On the other hand, the subclass having frequent flares are found to show H{alpha} emissions of similar strength in their spectra as that recorded with only a single flare but similar effective temperature, implying that the chromospheric activity may not be the only reason of triggering eruptions.

Cone search capability for table J/MNRAS/523/2193/table1 (Summary of properties of 125 flare stars from the first two-year survey of TMTS)