APMPM J0559-2903: The coolest extreme subdwarf known

We present the discovery of the coolest extreme subdwarf known to date. APMPM J0559-2903 was measured to be esdM7. Unlike for solar metallicity dwarfs, there are no very late type objects known among the extreme subdwarfs. APMPM J0559-2903 was discovered in a new southern high proper motion survey. Follow up spectroscopy at Keck was used to identify the spectral type with the help of spectral indices. Using the NextGen grid of model atmospheres by Hauschildt et al. (1999) we measured the effective temperature to be 3100 K and the metallicity to be MH=-1.5. The theoretical parameters place APMPM J0559-2903 at a distance of 100 pc with a space velocity of 260 km s(-1) relative to the local standard of rest.