XMM-Newton and NICER Measurement of the Rms Spectrum of the Millihertz Quasiperiodic Oscillations in the Neutron-star Low-mass X-Ray Binary 4U 1636-53

Ming Lyu ... [et al.].

Serie: Trabajos publicados del IAR ; no. 1547

Resumen: We used two XMM-Newton and six Neutron Star Interior CompositionExplorer observations to investigate the fractional rms amplitude of themillihertz quasiperiodic oscillations (mHz QPOs) in the neutron-starlow-mass X-ray binary 4U 1636-53. We studied, for the first time, thefractional rms amplitude of the mHz QPOs versus energy in 4U 1636-53down to 0.2 keV. We find that, as the energy increases from ∼0.2 to ∼3keV, the rms amplitude of the mHz QPOs increases, different from thedecreasing trend that has been previously observed above 3 keV. Thisfinding has not yet been predicted by any current theoretical model;however, it provides an important observational feature to speculatewhether a newly discovered mHz oscillation originates from themarginally stable nuclear burning process on the neutron-star surface.