A&A Supplement series, Vol. 128, March I 1998, 349-357
Received December 16, 1996; accepted August 1, 1997
R. Danner 
Max-Planck-Institut für Extraterrestrische Physik,
Giessenbachstraße, 85748 Garching, Germany 
Palomar Observatory, California Institute of Technology,
Pasadena, CA 91125, USA
This is the second in a series of three papers constraining the number of
detectable old neutron stars in the Galaxy.
Here, I present the statistical analysis of a sample of X-ray sources
coincident with areas of dark clouds in the Galactic plane. I compare
this sample with all sources in the ROSAT All-Sky Survey
bright source catalog within 
of the Galactic plane.
I present the results of an identification program of a subset of
sources that are compatible with a soft, thermal X-ray spectrum
and an effective source temperature of less than 70eV.
The three brightest sources in this sample form an intriguing subgroup.
One of them is a previously identified candidate for an accreting
neutron star. I identify the other two sources with hot white dwarf
stars. I find no new accreting neutron star candidate in this sample.
Based on this result, I derive an upper limit to the space density of
accreting neutron stars in fields of Galactic dark clouds of 
at a count rate 
.
keywords: surveys -- X-rays: stars -- stars: neutron; white dwarfs