  The X-ray source 1RXS J180431.1-273932 has been proposed as a new member of
the symbiotic X-ray binary (SyXB) class of systems, which are composed of a
late-type giant that loses matter to an extremely compact object, most likely a
neutron star. In this paper, we present an optical campaign of imaging plus
spectroscopy on selected candidate counterparts of this object. We also
reanalyzed the available archival X-ray data collected with XMM-Newton. We find
that the brightest optical source inside the 90% X-ray positional error circle
is spectroscopically identified as a magnetic cataclysmic variable (CV), most
likely of intermediate polar type, through the detection of prominent Balmer,
He I, He II, and Bowen blend emissions. On either spectroscopic or statistical
grounds, we discard as counterparts of the X-ray source the other optical
objects in the XMM-Newton error circle. A red giant star of spectral type M5
III is found lying just outside the X-ray position: we consider this latter
object as a fore-/background one and likewise rule it out as a counterpart of
1RXS J180431.1-273932. The description of the X-ray spectrum of the source
using a bremsstrahlung plus black-body model gives temperatures of around 40
keV and around 0.1 keV for these two components, respectively. We estimate a
distance of about 450 pc and a 0.2-10 keV X-ray luminosity of about 1.7e32
erg/s for this system and, using the information obtained from the X-ray
spectral analysis, a mass of about 0.8 solar masses for the accreting white
dwarf (WD). We also confirm an X-ray periodicity of 494 s for this source,
which we interpret as the spin period of the WD. In summary, 1RXS
J180431.1-273932 is identified as a magnetic CV and its SyXB nature is
excluded.
