We present observations of the active M-dwarf binary AT Mic (dM4.5e+dM4.5e)
obtained with the orbital observatory AstroSat. During 20 ks of observations,
in the far ultraviolet (130β180 nm) and soft X-ray (0.3β7 keV) spectral
ranges, we detected both quiescent emission and at least five flares on
different components of the binary. The X-ray flares were typically longer than
and delayed (by 5β6 min) with respect to their ultraviolet counterparts, in
agreement with the Neupert effect. Using X-ray spectral fits, we have estimated
the parameters of the emitting plasma. The results indicate the presence of a
hot multi-thermal corona with the average temperatures in the range of βΌ7β15 MK and the emission measure of βΌ(2.9β4.5)Γ1052cmβ3; both the temperature and the emission measure increased
during the flares. The estimated abundance of heavy elements in the corona of
AT Mic is considerably lower than at the Sun (βΌ0.18β0.34 of the solar
photospheric value); the coronal abundance increased during the flares due to
chromospheric evaporation. The detected flares had the energies of βΌ1031β1032 erg; the energy-duration relations indicate the presence of
magnetic fields stronger than in typical solar flares.Comment: Accepted for publication in Research in Astronomy and Astrophysic