We investigate the spectral and timing properties of the millihertz quasi-periodic oscillations ( mHz QPOs ) in neutron-star low-mass X-ray binary 4U 1636–53 using XMM-Newton and Rossi X-ray Timing Explorer ( RXTE ) observations .
The mHz QPOs in the XMM-Newton/RXTE observations show significant frequency variation and disappear right before type I X-ray bursts .
We find no significant correlation between the mHz QPO frequency and the temperature of the neutron-star surface , which is different from theoretical predictions .
For the first time we observed the full lifetime of a mHz QPO lasting 19 ks .
Besides , we also measure a frequency drift timescale \sim 15 ks , we speculate that this is the cooling timescale of a layer deeper than the burning depth , possibly heated by the previous burst .
Moreover , the analysis of all X-ray bursts in this source shows that all type I X-ray bursts associated with the mHz QPOs are short , bright and energetic , suggesting a potential connection between mHz QPOs and He-rich X-ray bursts .