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A new two-pole accretion polar: RX J1846.9+5538

R. Schwarz·J. Greiner·G. H. Tovmassian·S. V. Zharikov·W. Wenzel
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Abstract

We report the discovery of a new, bright (V = 17 mag) AM Her system as the optical counterpart of the soft ROSAT All-Sky-Survey source RX J1846.9+5538 (= 1RXS J184659.4+553834). Optical photometric and spectroscopic follow-up observations reveal a single period of 128.7 min, consistent with a high degree of spin-orbit synchronization, and a low polar field strength ($B<20$ MG) of the primary accretion region. The system was observed in optical intermediate and high states that differ by about 1 mag. These brightness variations were accompanied by a correlated change of the optical light curve, which we interpret as a switch between one- and two-pole accretion. This explanation is also supported by the X-ray light curves, which at two different epochs display emission from two equally bright accretion regions separated by 160 degrees. Both spots possess distinct spectral X-ray properties as seen from the X-ray hardness ratio, where the secondary accretion region appears significantly softer, thus probably indicating a higher field strength compared to the primary region. In all ROSAT pointings a deep dip is present during the primary flux maxima, very likely caused by absorption in one of the accretion streams.

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R. Schwarz, J. Greiner, G. H. Tovmassian, S. V. Zharikov, W. Wenzel. 2002-08-29. A new two-pole accretion polar: RX J1846.9+5538. https://doi.org/10.1051/0004-6361%3A20021193

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