Using the example of a still unidentified ‘‘serendiptious’’ X‐ray source in the field of the nearby galaxy NGC 1313, we describe a procedure for determining if unidentified x‐ray sources are likely compact objects. The very high X‐ray to optical flux ratio and other unusual properties of the X‐ray source MS 0317.7–6647 eliminate all the usual classes of optical counterparts except for either a very massive X‐ray binary (and Black Hole candidate) in NGC 1313 or a very nearby (∼100 pc) isolated neutron star slowly accreting interstellar matter. The presence of an IR cirrus cloud which shadows the 1/4 keV X‐ray background in this field supports the latter possibility. © 1994American Institute of Physics.