NICER observation list: Target ID 358901

Among many magnetic CVs, AR Sco stands out as the only known white dwarf pulsar binary where its pulsed emission from the radio to UV bands is powered by synchrotron emission from relativistic electrons, instead of mass accretion. It is unclear whether its pulsed X-ray emission is non-thermal or an extension of the synchrotron radiation beyond the UV band. NICER will unambiguously determine the nature of the pulsed X-ray emission and measure its spectral parameters accurately. The proposed NICER observation offers a unique opportunity to probe how interactions between the magnetic white dwarf and its companion star can accelerate particles and emit high-energy radiation, as originally proposed by Goldreich and Lynden-Bell in 1969 for the Jupiter-Io system, outside the solar system.