CzeV502 - an M Dwarf Near the Leo Triplet with Very Strong Flares

Discovery of flares in the M dwarf CzeV502 and our follow-up results are presented. We classify it as a dMe eruptive variable of UV Ceti type due to the X-ray activity, measured B − V of 1.5 mag, Hα emission, and flares. Our monitoring revealed only one reliable and one suspected superflare in 58 nights (210 hrs). The strongest flare with ΔR = 1.5 mag (ΔB ≈ 6-8 mag) could have a total energy of 3E+34 erg. The ASAS-SN data may contain 4 events up to ΔV of 0.43 mag and 12.55 d periodicity corresponding to the rotation or possible binarity. Other brightenings in sky survey (ASAS-3, CRTS, NSVS, and KWS) are doubtful. No event was unveiled on the 1 600 photographic plates. The upper rate limit of 1-2 superflares/1 640 hrs corresponds to activity several orders higher than for other M-dwarfs, especially, for the slow rotators. The low amplitude flares (ΔB < 0.5 mag) may be common (1 flare/4 hrs).

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