Stellar flares serve as crucial indicators for stellar magnetic activity. Radio emissions were detectable across all stages of stellar evolution. We defined radio stars in our paper as stars with radio continuum emission in the frequency region of about 1.4-375GHz from the catalogue published by Wendker (1995A&AS..109..177W, Cat. II/199, 2015 update, Cat. VIII/99). We also included detected radio stars from the LOFAR Two-metre Sky Survey (LoTSS), Australian Square Kilometre Array Pathfinder (ASKAP) and VLA Sky Survey (VLASS) surveys provided by previous work, and conducted comparative discussions. We utilize the light curves from the Transiting Exoplanet Survey Satellite (TESS) survey, coupled with low- and medium-resolution spectra from the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) survey, to investigate the magnetic activity and statistical properties of radio stars. We cross-matched the radio stars from the radio star catalogue and the LoTSS, ASKAP and VLASS surveys with TESS survey. For the stars from the radio star catalog, we obtained a matched sample of 1537 stars (hereafter called "Sample 1") and downloaded their TESS light curves, which included 4001 light curves at a 120-second cadence. For the stars from the LoTSS, ASKAP and VLASS surveys, we obtained a matched sample of 98 stars (hereafter called "Sample 2") and downloaded their 120-second TESS light curves, totaling 260. Subsequently, we employed repeated fitting techniques to distinguish stellar background light curves from flare events. For Sample 1, we successfully identified 12,155 flare events occurring on 856 stars. For the Sample 2, totally 3992 flare events were identified on 86 stars. Furthermore, by cross- referencing our samples with the Gaia survey, TESS Input Catalog, and LAMOST survey, we obtained additional stellar parameters, facilitating the determination of relationships between stellar and flare parameters. For stars in Sample 1, within the 12155 flare events observed on the 856 flare-active radio stars, a majority more than 97% had durations of less than 2 hours, while for stars in Sample 2, all 3992 flare events have a duration of less than two hours. We calculated the flare occurrence percentage for each flare-active radio star, observing a decrease as effective temperature increased for both Sample 1 and Sample 2. We derived values of power-law index (For Sample 1, alpha value approximately 1.50(0.11) for single stars and 1.38(0.09) for binary stars, for Sample 2, alpha value is about 1.47(0.11) for single stars and 1.42(0.09) for binary stars) for the cumulative flare frequency distribution. In both Sample 1 and Sample 2, stars with lower effective temperatures tended to exhibit increased activity. Utilizing LAMOST spectra and Gaia DR3 chromospheric activity index, we noted that the Halpha equivalent width and Gaia Ca II IRT activity index of flare-active radio stars was significantly larger than that of non-flare stars. An intriguing finding was the potential identification of a coronal rain candidate through the asymmetry observed in the Halpha line.
Cone search capability for table J/A+A/686/A164/table1 (Parameters of TESS radio stars)
