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*, Guobao Zhang, Mariano Méndez, D. Altamirano, G. C. Mancuso, Fu-Yuan Xiang, Huaping Xiao

*Corresponding author for this work

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We used two XMM-Newton and six Neutron Star Interior Composition Explorer observations to investigate the fractional rms amplitude of the millihertz quasiperiodic oscillations (mHz QPOs) in the neutron-star low-mass X-ray binary 4U 1636-53. We studied, for the first time, the fractional rms amplitude of the mHz QPOs versus energy in 4U 1636-53 down to 0.2 keV. We find that, as the energy increases from ∼0.2 to ∼3 keV, the rms amplitude of the mHz QPOs increases, different from the decreasing trend that has been previously observed above 3 keV. This finding has not yet been predicted by any current theoretical model; however, it provides an important observational feature to speculate whether a newly discovered mHz oscillation originates from the marginally stable nuclear burning process on the neutron-star surface.
Original languageEnglish
Article number120
Number of pages6
JournalThe Astrophysical Journal
Issue number2
Publication statusPublished - 3-Jun-2020


  • Low-mass x-ray binary stars
  • Neutron stars
  • Astrophysical explosive burning
  • QPOS
  • LINE

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