The hard X-ray source 2PBC J0658.0-1746 was proposed as an eclipsing magnetic cataclysmic variable of the polar type , based on optical follow-ups .
We present the first spectral and timing analysis at X-ray energies with XMM-Newton , complemented with archival X-ray , optical , IR photometry and spectroscopy .
The X-ray emission shows bright and faint phases and total eclipses recurring every 2.38 h , consistent with optical properties .
This firmly identifies 2PBC J0658.0-1746 as an eclipsing polar , the second hard X-ray selected in the orbital period gap .
The X-ray orbital modulation changes from cycle-to-cycle and the X-ray flux is strongly variable over the years , implying a non-stationary mass accretion rate both on short and long timescales .
The X-ray eclipses allow to refine the orbital ephemeris with period 0.09913398 ( 4 ) d , and to constrain the binary inclination 79 ^ { o } \lesssim i \lesssim 90 ^ { o } and the mass ratio 0.18 < M _ { 2 } / M _ { WD } < 0.40 .
A companion mass M _ { 2 } = 0.2 - 0.25 M _ { \odot } with a radius R _ { 2 } = 0.24 - 0.26 R _ { \odot } and spectral type \sim M4 , at D = 209 ^ { +3 } _ { -2 } pc , is derived .
A lower limit to the white dwarf mass of \sim 0.6 M _ { \odot } is obtained from the X-ray spectrum .
An upper limit to the magnetic colatitude , \beta \lesssim 50 ^ { o } , and a shift in azimuth , \psi \sim 14 ^ { o } , of the main accreting pole are also estimated .
The optical/IR spectral energy distribution shows large excess in the mid-IR due to lower harmonics of cyclotron emission .
A high-state mass accretion rate \sim 0.4 - 1 \times 10 ^ { -10 } M _ { \odot } yr ^ { -1 } , lower than that of cataclysmic variables above the gap and close to that of systems below it , is estimated .
With 2PBC J0658.0-1746 , the number of hard X-ray selected polars increases to thirteen members , suggesting that they are not as rare as previously believed .