The persistent X-ray source 4U 0142+614 was discovered by UHURU and soon
noticed to possess an ultrasoft spectrum. In the X-ray
colour-colour diagram of White & Marshall (1984) it occupies the same
region of black hole candidates in their ``high state", such as
LMC X-3, LMC X-1 and A 0620-00. 4U 0142+614 lies in the galactic plane
(l=129 
.4, b=-0 .4) and, despite its small
error circle (a few arcsec),
no optical or radio
counterparts have yet been identified (White et al. 1987). While the X-ray
luminosity of 4U 0142+614 ( 
(d/4 kpc) 
erg s 
) is
1-2 orders of magnitude
lower than that measured for the sources above, its spectrum
(power law with energy index of 3-4) is reminiscent of
high state black hole candidates.
During one of three EXOSAT observations of 4U 0142+614 carried out in
1984-1985, an
additional spectral component was detected above 3 keV within the
arcmin collimator response of the Medium Energy (ME) experiment.
Correspondingly, 25 min periodic oscillations were discovered in
the 3-10 keV energy range (White et al. 1987).
Mereghetti, Stella & De Nile (1993) pointed out that this component and
the 25 min oscillations could originate from a nearby source in
the ME field of view, namely RX J0146.9+6121, an X-ray transient
discovered with ROSAT and identified with the Be star
LSI +61 235 (Motch et al. 1991).