We present spectroscopic observations of two halo M subdwarfs which have H \alpha emission lines .
We show that in both cases close companions are the likely cause of the chromospheric activity in these old , metal-poor stars .
We argue that Gl 781 A ’ s unseen companion is most likely a cool helium white dwarf .
Gl 455 is a near-equal-mass M subdwarf ( sdM ) system .
Gl 781 A is rapidly rotating with v \sin i \approx 30 km s ^ { -1 } .
The properties of the chromospheres and X-ray coronae of these systems are compared to M dwarfs with emission ( dMe ) .
The X-ray hardness ratios and optical chromospheric line emission ratios are consistent with those seen in dMe stars .
Comparison to active near-solar metallicity stars indicates that despite their low metallicity ( [ m / H ] \approx - 1.2 ) , the sdMe stars are roughly as active in both X-rays and chromospheric emission .
Measured by L _ { X } / L _ { bol } , the activity level of Gl 781 A is no more than a factor of 2.5 subluminous with respect to near-solar metallicity stars .