X-ray Timing Studies of Black Holes and Neutron Stars

Millisecond timing signals, such as Quasi-periodic Oscillations (QPOs) seen in the X-ray light curves of accreting black holes and neutron stars are from the vicinity of black holes and neutron stars. The time scales of the High Frequency (HF) QPOs in black hole binaries or killohertz (kHz) QPOs in neutron star Low Mass X-ray Binaries (LMXBs), are comparable to the dynamical time scales in the vicinity of black holes and neutron stars, giving direct constraints on the size (e.g., the marginally stable circular orbit, ISCO) of the black holes or neutron stars. Other QPOs at lower frequencies, such as Low Frequency (LF) QPOs in black hole X-ray binaries and neutron star LMXBs, are suspected to correspond to the Lense-Thirring (LT) precession. Similarly, the millihertz QPOs seen in NS LMXBs probably correspond to some special modes of thermonuclear burning of accreted matter on neutron star surface. In comparison, rapid thermonuclear burning on these accreting neutron stars would turn out as type I x-ray bursts, of which the typical time scale is about 20 seconds. Not surprising, during these type I bursts, with X-ray observatories with timing capabilities, we can detect fast spin rates of neutron stars in LMXBs, the progenitor of the radio millisecond pulsars.

We make use of space observations with the RXTE, XMM-Newton, Swift and HXMT to study timing signals from accreting black holes and neutron stars. In the future, we look forward to future X-ray timing missions: eXTP and LOFT. These missions would make significant progress on scientific topics such as The Probe of Ultra-dense Matter with X-ray Timing.

Here below are the reviews about the field:

Representative Publications:

[ version last updated: 2017.10.10 wenfei @shao.ac.cn ]