NICER observation list: Target ID 463901

Quasi-periodic oscillations (QPOs) at frequencies of millihertz (mHz) have only been reported in a few neutron star (NS) systems since their discovery. Given their close relation with the occurrence of type I X-ray bursts, numerical simulations strongly suggest that mHz QPOs are due to a special mode of burning, called 'marginally stable nuclear burning'. However, even though model predictions agree well with the observations, there are still many open questions. Here we propose, after having detected the mHz QPOs with any instrument, and within the next few days, 50 ksec ToO observations to study the mHz QPOs in the next NS system that shows them. These observations will allow us to test whether the oscillations can be described as temperature fluctuations originating on the NS surface.