  We present the first X-ray observations with the XMM-Newton and INTEGRAL
satellites of the recently discovered cataclysmic variable
1RXSJ173021.5-055933, together with simultaneous UV and coordinated optical
photometry aiming at characterising its broad-band temporal and spectral
properties and classifying this system as a magnetic one. We find that the
X-ray light curve is dominated by the 128s spin period of the accreting white
dwarf in contrast to the far-UV range, which turns out to be unmodulated at a
3sigma level. Near-UV and optical pulses are instead detected at twice the spin
frequency. We identify the contributions from two accreting poles that imply a
moderately inclined dipole field allowing, one pole to dominate at energies at
least up to 10keV, and a secondary that instead is negligible above 5keV. X-ray
spectral analysis reveals the presence of multiple emission components
consisting of optically thin plasma with temperatures ranging from 0.17keV to
60keV and a hot blackbody at ~90eV. The spectrum is also strongly affected by
peculiar absorption components consisting of two high-density
(~3x10^(21)cm^(-2) and ~2x10^(23)cm^(-2)) intervening columns, plus a warm
absorber. The last is detected from an OVII absorption edge at 0.74keV, which
suggests that photoionization of pre-shock material is also occurring in this
system. The observed properties indicate that the accretor in
1RXSJ173021.5-055933 is a white dwarf with a likely weak magnetic field, thus
confirming this cataclysmic variable as an intermediate polar (IP) with one of
the most extreme spin-to-orbit period ratios. This system also joins the small
group of IPs showing a soft X-ray reprocessed component, suggesting that this
characteristics is not uncommon in these systems.

Astrophysics