ON THE OPTICAL COUNTERPART OF 1E 1207-4-5209, THE CENTRAL X-RAY SOURCE OF A RING-SHAPED SUPERNOVA REMNANT

The shell-like SNR PKS 1209-52 contains an unresolved X-ray source near its geometrical center. This source, 1E 1207.4-5209, has a flux of approximately 4 x 10(-12) ergs cm-2 s-1 and was observed both by EXOSAT and the Einstein HRI. An ESO NTT observation revealed the presence of only two objects in and near the recently revised error box. Of these, the brightest (m(v) = 17.37) was already known to be a field K star. Surprisingly, spectroscopy of the fainter object (m(v) = 19.04) also reveals it to be a normal K star. The X-ray source counterpart remains unseen down to m(v) less-than-or-equal-to 24, in spite of its accurate position in a relatively uncrowded field. Its suggested association with the SNR, and relevant implications, should be reconsidered, in view of its f(x)/f(v) of > 1000.