ISOPHOT-S OBSERVATIONS OF 3M DWARFS

The M dwarfs GL 832 (spectral type M2), GL 887 (M1), and GL 1 (M2) hav e been observed with the ISOPHOT spectrophotometers in the range 2.5-1 2 mu m at high signal-to-noise ratios. Since optical and ground based near-infrared data are also available, more than 95 % of the total flu x is now covered for these objects. It is seen that between 2.5 mu m a nd about 9 mu m the fluxes fall off faster than a Rayleigh-Jeans tail of a black body distribution and that for longer wavelenghts the decli ne is smaller. This indicates that the ISO data are probing the region around the temperature minimum and that our stars have some kind of c hromosphere although Ha emission is not observed. Comparison with a mo del indicates that the features are considerably weaker than predicted .