XMM-Newton and NICER measurement of the rms spectrum of the millihertz quasi-periodic oscillations in the neutron-star low-mass X-ray binary 4U 1636-53

Abstract

We used two XMM-Newton and six Neutron Star Interior Composition Explorer (NICER) observations to investigate the fractional rms amplitude of the millihertz quasi-periodic 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 vs. energy in 4U 1636-53 down to 0.2 keV. We find that, as the energy increases from 0.2 keV 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.

Published in ApJ, 10 pages, 5 figures

References in corpus (8)

• Millihertz Oscillation Frequency Drift Predicts the Occurrence of Type I X-ray Bursts
• Ignition latitude and the shape of Type I X-ray bursts
• Reaction Rate and Composition Dependence of the Stability of Thermonuclear Burning on Accreting Neutron Stars
• The 2015 outburst of the accretion-powered pulsar IGR J00291+5934: INTEGRAL and Swift observations
• Millihertz quasi-periodic oscillations in 4U 1636-53 associated with bursts with positive convexity only
• Discovery of a soft X-ray 8 mHz QPO from the accreting millisecond pulsar IGR J00291+5934
• Discovery of an accretion-rate independent absolute RMS amplitude of millihertz quasi-periodic oscillations in 4U 1636-53
• Ionisation state of the accretion disc in the neutron-star low-mass X-ray binary 4U 1728-34

Cited by in corpus (5)

• The evolution of the high-frequency variability in the black hole candidate GRS 1915+105 as seen by RXTE
• Detection of millihertz quasi-periodic oscillations in the low-mass X-ray binary 4U 1730--22 with NICER
• Drifts of the marginally stable burning frequency in the X-ray binaries 4U 1608--52 and Aql X--1
• The harmonic component of the millihertz quasi-periodic oscillations in 4U 1636-53
• The mHz quasi-regular modulations of 4U 1630--47 during its 1998 outburst