The x-ray emission from LSI+61 was measured on 9 occasions with the ROSAT observatory between 11 August and 4 September 1992. The results are listed in table 2. Integration times ranged from about one thousand to a few thousand seconds. The detector measured photon events in 34 spectral bins within the energy range 0.07 to 2.48 KeV. The photon counts at the position of LSI+61 listed in table 2, were obtained by summing the counts over all energy bins at the position of the star. The counts have been corrected for a background level derived from an annular region surrounding LSI+61 that did not contain any detectable x-ray sources. For the short integration times used, the background count rate was very small, and did not significantly affect the on-source count rate.
The energy flux in the 0.07 to 2.48 keV band was derived by fitting
the observed spectral distribution to power law, blackbody and optically-thin thermal
energy spectra. The signal-to-noise level per energy bin was not
sufficient to discriminate between these spectral models.
However, to assess the sensitivity of the calculated flux on the
spectral model, we derived values for each case. The shape of the low
energy portion of the x-ray
spectrum is dominated by the effects of absorption by neutral gas in
the intervening interstellar medium. The atomic hydrogen column density
to LSI+61 has been measured by Frail & Hjellming (1991).
For the spectral fits we used their
value of 
cm
. The fits are therefore
functions of only two parameters, a normalization parameter and a
parameter that measures the spectral shape; the power law index in
the case of the power law, and the temperature in the case of
blackbody or optically-thin thermal emission.
Assuming a power law spectrum, the average fitted spectral index over
the three observations with total counts about 500 is 2.0 
0.14.
For the blackbody and optically-thin thermal models, the average fitted temperature
for the same observations is 0.26 0.06 and 0.8 0.1 keV
respectively.
As expected, the calculated source flux is only weakly dependent
on the spectral model assumed.
In figure 2, the observed x-ray flux is plotted versus Julian Date for each
of the three models. There is a strong modulation of the x-ray flux,
from a low value of 
to a high value of 
erg cm s
.
The transition from a high to a low state and back to a high state
occurs on a time scale of 20 days; similar to the orbital period.
For a distance of 2.3 kpc, the peak
luminosity before correction for absorption is 
ergs s.
The derivation of the corresponding unabsorbed luminosity is dependent on the
spectral model and ranges from one to several 
ergs s.