Radio continuum observations of possible B-type stars in the halo of M 31

We present Very Large Array (VLA) 5 GHz continuum observations of six point sources towards the halo of M 31, which have featureless optical spectra a nd magnitudes ranging from V=21.5-22.2, in order to determine whether these objects are BL Lacs. No radio emission coincident with the optical positio ns is detected to a 5 sigma noise level of between 0.08 and 0.11 mJy. The r esulting upper limits to the two-point radio-to-optical spectral indexes fr om 5 GHz to 2500 Angstrom (alpha(RO)) are less than 0.30 for all of the sam ple. These observations make it highly likely that these objects are not BL Lacs, and hence strengthens the case that they are normal B-type stars in the halo of M 31.