Identification of strong photometric activity in the components of LHS 1070

Context. Activity in low-mass stars is an important ingredient in the evolution of such objects. Fundamental physical properties such as age, rotation, magnetic field are correlated with activity. Aims. 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. Methods. Time-series CCD observations were used to monitor LHS 1070 in the B and IC bands. H-band data were used to obtain accurate astrometry for the LHS 1070A/(B+C) system. Results. We have found that two components of the triple system LHS 1070 exhibit photometric activity. We identified that compo-nents A and B are the flaring objects. We estimate the total energy, ∼ 2.0 × 1033 ergs, and the magnetic field strength, ∼ 5.5 kG, of the flare observed in LHS 1070 B. This event is the largest amplitude, ∆B & 8.2 mag, ever observed in a flare star. Conclusions