Han-Tang Lin(NCU) ; Wen-Ping Chen(NCU);Chia-Lung Lin(NCU);Wing Ip(NCU);Jinzhong Liu(Xinjiang Astronomical Observatory)
Our Sun produces flares, eruptive events caused by reconnection of surface magnetic field lines near sunspots. Some M dwarfs, the later spectral types the more so, being more convective, are even more prone to such flare events, with more frequent occurrence rates and significantly more energetic during the flares in comparison to the quiescent photospheric luminosities. Here we report the optical flare ac- tivity of Wolf 359 (GJ409; CN Leo). This relatively young (< 1 Gyr) red dwarf (M6.5 Ve), being the fifth nearest stellar system (2.4 pc) to the Sun, is known for its frequent optical flares, along with gamma-ray and X-ray bursts. Our data consist of 25 hours spanning 7 days in April 2020 of photometric monitor- ing with two small telescopes in Xinjiang, including a one-meter and one of the TAOS 0.5 m telescopes relocated in 2020 from Lulin Observatory. A total of 13 flares with energies greater than 10^29 ergs were detected, including one "superflare" event (≈ 10^32ergs) observed by two telescopes, implying an average occurrence rate of one flare per two hours. With a mass barely above the hydrogen fusion limit, thereby being fully convective to facilitate dynamo magnetism, the red dwarf Wolf 359 is known to host two plan- ets. It remains to be investigated if a close-in companion serves to anchor and twist the field lines so as to play a key role in the repeated reconnection events. Moreover, the two-telescope observations, each with a different sampling function, of a single event allow us to estimate the "underlined" flare profile. We present how the flare parameters, such as the rising/heating time scale, peak amplitude, decay/cooling time scale, are estimated using two separately sampled light curves. We also discuss how sampling effects the derived total energy of a flare, and the detectability (of the peak) of an event.