In this paper, we study stellar light curves from the Transiting Exoplanet Survey Satellite (TESS) for the presence of stellar flares. The main aim is to detect stellar flares using 2 minute cadence data and to perform a statistical analysis. To find and analyze stellar flares, we prepared the automatic software WARPFINDER. We implemented three methods described in this paper: trend, difference, and profile fitting. Automated searches for flares was accompanied by visual inspection. Using our software we analyzed the 2 minute cadence light curves of 330,000 stars located in the first 39 sectors of TESS observations. As a result, we detected over 25,000 stars showing flare activity with the total number of more than 140,000 flares. This means that about 7.7% of all the analyzed objects are flaring stars. The estimated flare energies range between 1031 and 1036 erg. We prepared a preliminary preview of the statistical distribution of parameters such as the flare duration, amplitude, and energy, and compared it with previous results. The relationship between stellar activity and spectral type, temperature, and mass was also statistically analyzed. Based on the scaling laws, we estimated the average values of the magnetic field strength and length of the flare loops. In our work, we used both single (about 60%), and double (about 40%) flare profiles to fit the observational data. The components of the double profile are supposed to be related to the direct heating of the photosphere by nonthermal electrons and back-warming processes.

We studied the light curves of GJ 1243, YZ CMi, and V374 Peg, as observed by TESS, for the presence of stellar spots and stellar flares. One of the main goals was to model the light curves of the spotted stars to estimate the number of spots, along with their parameters, using our original BASSMAN software. The modeled light curves were subtracted from the observations to increase the efficiency of the flare detection. The flares were detected automatically with our new dedicated software, WARPFINDER. We estimated the presence of two spots on GJ 1243, with a mean temperature of about 2800 K and a spottedness varying between 3% and 4% of the stellar surface, and two spots on V374 Peg, with a mean temperature of about 3000 K and a spottedness of about 6% of the stellar surface. On YZ CMi, we found two different models for two light curves separated in time by 1.5 yr. One of them was a three-spot model, with a mean temperature of about 3000 K and a spottedness of about 9% of the stellar surface. The second was a four-spot model, with a mean temperature of about 2800 K and a spottedness of about 7% of the stellar surface. We tested whether the flares were distributed homogeneously in phase and where there was any correlation between the presence of spots and the distribution of the flares. For YZ CMi, one spot was in anticorrelation with the distribution of the flares, while GJ 1243 shows the nonhomogeneous distribution of flares.

The study is devoted to search for flare stars among confirmed members of Galactic open clusters using high-cadence photometry from TESS mission. We analyzed 957 high-cadence light curves of members from 136 open clusters. As a result, 56 flare stars were found, among them 8 hot B-A type objects. Of all flares, 63 % were detected in sample of cool stars (T eff < 5000 K), and 29 % -in stars of spectral type G, while 23 % in K-type stars and approximately 34% of all detected flares are in M-type stars. Using the FLATW'RM (FLAre deTection With Ransac Method) flare finding algorithm, we estimated parameters of flares and rotation period of detected flare stars. The flare with the largest amplitude appears on the M3 type EQ Cha star. Statistical analysis did not reveal any direct correlation between ages, rotation periods and flaring activity.

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