报告题目：X-ray spectral state transitions in X-ray binaries：accretion physics towards the extremes

报 告 人：Dr. Wenfei Yu, SHAO

报告时间：2018-03-22 14:00

报告地点：蒙民伟科技南楼S727

报告摘要：Observations of black hole and neutron star X-ray binaries in the past few decades have helped shape current knowledge of accretion onto compact objects, which is also important to the understanding of black hole growth and galaxy evolution on the cosmological time scales. Manifestations of popular black hole accretion models, such as standard geometrically thin disk model, advection-dominated accretion flow (ADAF) model and slim disk model, have all been found in X-ray binaries, forming the current framework of accretion regimes in relative to mass accretion rate onto black holes. In this talk, I will first introduce X-ray spectral state transitions observed in black hole and neutron star X-ray binaries, and then show evidence that an additional parameter, other than the mass accretion rate, is needed to describe the observations. The observations of the outbursts of black hole and neutron star LMXB transients imply a 2-D framework of non-stationary accretion regimes in which the rate-of-change of the mass accretion rate is not negligible. In the end, I will show X-ray spectral state transitions observed in black hole and neutron star X-ray binaries corresponding to extremely low and high mass accretion rate, as well as several cases associated with extreme rate-of-change of the mass accretion rate. I will conclude by pointing out that we need to understand non-stationary accretion regimes and the effects of disk mass in black hole accretion theory.