摘要
Microquasars are the compact objects generally including accreting black holes which produce relativistic jets.The physical mechanisms of jet launching,collimation,and acceleration are poorly understood.Microquasars show strong variability in multi-wavelength observations.In x-rays,the sources show the fast variation features down to millisecond time scales,with the prominent quasiperiodic oscillations(QPOs)around 0.1 Hz–tens of Hz in light curves,however,physical origin of QPOs is still uncertain.FAST as the largest radio telescope provides the opportunity to study fast variability of both radio flux and polarization in microquasars.In the FAST observations from 2020–2022,we reported the first evidence of radio subsecond quasi-periodic oscillations of GRS 1915+105,providing the direct link between QPOs and the dynamics of relativistic jets.These QPOs with the centroid frequency around 5 Hz are transient,accompanied with strong evolution of the spectral index.Combined with multiwavelength observations,we discuss the possible physical models to produce radio QPOs in BH systems:the helical motion of jet knots or precession of the jet base.In near future,high time resolution radio monitoring of microquasars based on FAST is expected to discover more new phenomena in black hole systems,which will be important for understanding the physics in strong gravity.
作者
Wei Wang
王伟(Department of Astronomy,School of Physics and Technology,Wuhan University,Wuhan 430072,China)
基金
supported by the National Natural Science Foundation of China(Grant No.12133007)
the National Key Research and Development Program of China(Grant Nos.2021YFA0718503 and 2023YFA1607901)
the Cultivation Project for FAST Scientific Payoff and Research Achievement of CAMS-CAS。
