2011A&A...525A..84A

Activity in low-mass stars is an important ingredient in their evolution. Fundamental physical properties such as age, rotation, and magnetic field are correlated with activity. We show that two components of the low-mass triple system LHS 1070 exhibit strong flaring activity. We identify the flaring components and obtained an improved astrometric solution for the LHS 1070A/(B +C) system. Time-series CCD observations were used to monitor LHS 1070 in the B and I_C bands. H-band data were used to obtain accurate astrometry for the LHS 1070A/(B+C) system. We find that two components of the triple system LHS 1070 exhibit photometric activity. We identified components A and B as the flaring objects. We estimate the total energy, ∼2.0x10³³erg, and the magnetic field strength, ∼5.5kG, of the flare observed in LHS 1070 B. This event has one of the largest amplitudes, ΔB >8.2mag, ever observed in a flare star.