Our observations show that LSI+61 is a persistent yet highly variable source of x-rays, with amplitude and time scale of variations similar to the periodic radio outbursts. It is interesting to examine the properties of this system in relation to known classes of high-mass, x-ray emitting stars.
Meurs et al. (1992) analysed the ROSAT all-sky survey data for the
majority of OB stars
in the Bright Star Catalogue. Roughly 10% of all OB or OBe stars
are detected with ROSAT, at luminosity ranging from 
erg 
. The detection rate increases toward earlier
spectral types, reaching close to 50% at B0, the spectral type of
LSI+61 . Meurs et al. attribute these x-ray luminosities to weak shocks
in the stellar winds of OB stars. The x-ray luminosity of LSI+61 , at
erg s
, is at the high end of this range. However,
the binary nature of LSI+61 and the high degree of modulation on the times
scale of the orbital period, argues against this interpretation for the
x-ray emission.
LSI+61 is one of a group of about 20 Be x-ray binary systems (van den Heuvel
& Rappaport 1987). These systems have orbital periods of
tens of days or longer, and the x-ray emission is considered
to arise from wind accretion onto a neutron star companion. Approximately
half of these objects show direct evidence for neutron star companions
in the form of x-ray pulsations. The non-pulsed emission is generally
transient or highly variable with outburst durations similar to the
orbital periods, luminosities in the keV range of 
erg s and hard spectra (kT
keV). These outbursts are
thought to occur as a result of
increased wind accretion rates on the neutron star companion due to a
combination of orbital eccentricity and irregular episodes of enhanced
equatorial mass loss from the Be stars (see van den Heuvel 1994).
The x-ray properties of LSI+61 contrast markedly with the other
members of this group.
The x-ray outbursts have much lower luminosity and a much softer spectrum
(kT 
keV). The single other exception is the
Be star X Per, which has a similar keV, x-ray luminosity. However LSI+61
further distinguishes itself by its strong, outbursting radio emission.
The radio properties of LSI+61 are similar to those of the ``standard''
high-mass x-ray binaries such as SS 433, Cyg X-3 and Cir X-1. In these
shorter period systems, the primary fills, or very nearly fills, its Roche
Lobe and sustained, high mass accretion rates onto the compact companion
can occur. However, the x-ray outbursts from this class in the keV range
are similar to those of the Be x-ray binaries; much harder and more
luminous by orders of magnitude than LSI+61 . If the COS-B
and GRO 
-ray emission is associated with LSI+61 , then luminosities
of 
in the MeV, and higher, energy range are inferred.
While these luminosities are
similar to the accretion generated keV luminosities of other high-mass
x-ray binaries, the shift to higher photon energies would point to a
fundamental difference in the accretion process.
LSI+61 does not fit easily into either of the two categories of high-mass
x-ray binaries. If the x-ray outburst is accretion generated, then the
data implies either a very low accretion rate compared to similar systems or
a spectrum of accretion generated photons that emerges primarily at
-rays. The peculiarity of LSI+61 relative to other x-ray binary systems,
leads us to examine other possibilities for the source of x-ray
emission.