  The variable sdB known as V46 in the globular cluster M4 has remained
enigmatic since its discovery almost 10 years ago. We present here radial
velocity measurements obtained from medium-resolution VLT/FORS2 spectra that
show variations at twice the period of the luminosity changes. This implies
that the system is an ellipsoidal variable. Unlike the other sdB binaries of
this nature, the fundamental parameters of this star we derive suggest that it
lies below the Zero Age Extreme Horizontal Branch. From the cluster distance
and the gravity we determine the mass of V46 to be ~0.19Msun. This is too low
to sustain core helium burning. From the mass function we derive a lower limit
for the companion of only 0.26Msun. We discuss the star's origin in the context
of close binary evolution in the field and globular clusters.
