ON THE NATURE OF THE 25-MIN PERIODICITY FROM 4U 0142- A NEARBY, SLOWLY SPINNING NEUTRON STAR(614 )BE SYSTEM/

The unidentified X-ray source 4U 0142+614 has an unusually soft spectr um and has shown a periodic modulation at approximately 25 minutes, wh ich could be interpreted as the orbital period of a Low Mass X-ray Bin ary. Recently a new X-ray source, probably a Be/neutron star system, h as been discovered at an angular distance of only 24 arcmin from 4U 01 42+614. We consider the possibility that the newly discovered source, RX J0146.9+6121, is responsible for the periodicity previously attribu ted to 4U 0142+614. If this interpretation is correct, RX J0146.9+6121 would be the most slowly rotating neutron star known. We present also new spectroscopic data on the optical counterpart of RX J0146.9+6121, that strengthen the similarity with other Be/neutron star binaries. T he nature of both sources is discussed in the light of the new interpr etation.