We report observations of a new AM Herculis binary identified as the optical counterpart of the X-ray source RX J1313.2–3259 , detected during the ROSAT All-Sky Survey ( RASS ) .
It has an orbital period of 251 min and is strongly modulated at optical wavelengths .
The long-term behavior is characterized by a pronounced variation in X-rays between the RASS and two subsequent pointings ( decrease by a factor 40 in count rate ) and by moderate changes in the optical brightness ( up to a factor 5 ) .
The X-ray spectrum is dominated by a soft quasi-blackbody component , with a smaller contribution from thermal bremsstrahlung .
Measurements of high circular polarization confirm its classification as a Polar with a magnetic field strength of 56 MG .
The average visual magnitude of RX J1313.2–3259 is V \simeq 16 ^ { m } , for its distance we get \simeq 200 pc .