Best-fitting synthetic SED from the PHOENIX stellar atmosphere models corresponding to spectral-type M with T = 3500 K, log g = 0.0 and E(B − V) = 0.03, in units of Vega mag. The average scatter between the SED and observed HST photometry σ = 0.05 mag. The shaded regions indicate the wavelength range of each of the filters. The red points denote the average measured magnitude in each of the HST filters.