Further Studies on Using Variability to Probe the Properties of Binary Orbit,

We propose to continue using variability to probe the properties of binary orbit, accretion diskand compact object of accreting binaries. The time scales of variability of accreting binaries rangingfrom less than a millisecond to thousands of days can be periodic, quasi-period or even aperiodic. Itallows us to probe different parts of the accreting binaries to learn the properties of theseastrophysical systems. We plan to continue using the Hilbert-Huang transform (HHT), which is apower tool for non-stationary oscillations and has been successfully applied some accreting systemsto resolve their unstable periodicity variations, to analyze the superorbital modulations andquasi-periodic oscillations (QPOs) of X-ray binaries to reveal the natures of these phenomena. In thisresearch, we will especially attempt to apply HHT to analyze the millihertz QPO, which is believe tobe caused by the marginally stable nuclear burning on the surface of accreting neutron star, to furtherunderstand this phenomenon. On the other hand, orbital period is the most fundamental physicalparameter of an accreting binary. The orbital period derivative can give us clue for the evolution ofthe binary system. In addition to the pointing observations, orbital modulations of many X-raybinaries can be resolved by the light curves collected by wide-filed monitoring or sky scanning typeof X-ray telescopes that allow us to continuously trace the orbital period changes of these accretingbinary systems. For an X-ray pulsar binary, not only the orbital period but also the orbital and spinparameters can be precisely determined by using pulsar timing. With the refined orbital and spinparameters, we are able to make pulsation phase-resolved spectra to study the emission mechanicsand physical parameters of neutron star, including the cyclotron resonance feature to directly measurethe magnetic field of on the surface of neutron star. Especially, we will participate an internationalproject, Large Synoptic Survey Telescope (LSST). Utilizing the unprecedented sky survey ability andthe advantage of the location of the site, it is able to process the constantly monitoring the long-termvariability of accreting binaries in optical-infrared band. Combined with the monitoring light curvesfrom X-ray band telescopes, we are able to further understand the natures of long-term modulationsof the accreting binaries.