The New Magnetic CV 1RXS J1016.9-4103: One More System in the Period Gap

We report phase resolved spectroscopy of a likely new polar in the ROSAT all-sky survey catalog. The X-ray source is soft (HR1 = -1.00 plus or minus 0.06) and relatively bright (C = 0.12), and the optical counterpart is relatively faint (V ~19). The spectra obtained at the Siding Spring 2.3-m telescope using the Double Spectrograph (DBS) clearly show radial velocity modulation on a period of 122.3 minutes. The system would therefore belong to a population of AM Her systems with orbital periods within the so-called period gap.