X-ray observation of AM Herculis in a very low state with Suzaku

Abstract

The X-ray observation of AM Herculis (AM Her) in a very low state was performed with Suzaku in 2008 October. One flare event with a timescale of ∼3700 s was detected at the X-ray luminosity of 6.0 × 1029 erg s-1 in the 0.5-10 keV band at the assumed distance of 91 pc. The X-ray spectrum is represented by a thermal plasma emission model with a temperature of 8.67+1.31-1.14 keV. During the quiescence in the flare interval, Suzaku also detected significant X-rays at a luminosity of 1.7 × 1029 erg s-1 in the 0.5-10 keV band, showing a clear spin modulation at a period of 0.1289273(2) days at BJD 2454771.581. The X-ray spectra in the quiescence were represented by a MEKAL + Power Law model or a single CEMEKL model, which are also supported by phase-resolved analyses. A correlation between the temperature and the volume emission measure was found together with historical X-ray measurements of AM Her in various states. In order to account for a possible non-thermal emission from AM Her, particle acceleration mechanisms in the AM Her system are also discussed, including the new proposal of a shock acceleration process on the top of the accretion column. © 2010. The American Astronomical Society. All rights reserved.