Wenfei Yu's Research Page

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Research highlights:

It has been generally thought that in  the quiescence of black hole and neutron star soft X-ray transients (SXTs), the accretion disk accumulates mass from the mass flow flow of the companion star. The mass is then accreted during outbursts. However, there have been no evidence in the SXts showing a correlation between the total fluence or amplitude and the outburst waiting time in the recent past. The reason might be that there is always significant mass remains after each outburst, which makes each outburst cycle not independent.

For the first time, we have found a nearly linear relation between the peak flux of the low/hard state and the outburst waiting time in a black hole SXT named GX 339-4 (Yu et al. 2007, ApJ, 663, 1309, see the figure below). The impact of this result is obvious; 1) GX 339-4 is a special source in which outbursts consume most of the mass accumulated in quiescence; 2) there is a relation between the hard X-ray peak flux and the mass in the disk. The physics for the later is not known yet, but apparently involves the generation of high energy radiation and the  importance of the outer disk flow in the accretion geometry. 

The hard-to-soft state transitions in GX 339-4

Dr. Wenfei Yu
Shanghai Astronomical Observatory
80 Nandan Road, Shanghai 200030
China
Phone: 86-21- 64279697
E-mail: wenfei at shao.ac.cn

Currently I am a senior research scientist corresponding to a full research professor position at Shanghai Astronomical Observatory (SHAO) of the Chinese Academy of Sciences. Before I joined SHAO, I had been a senior postdoctoral research associate at the  Center for Theoretical Astrophysics & Department of Physics of the University of Illinois at Urbana-Champaign (UIUC), where relativistic astrophyics and high energy astrophysics were the focuses. Even before, I worked as a postdoctoral fellow at the Astronomical Institute of the University of Amsterdam, the well-known center for high energy astrophysics of X-ray binaries. I got my Ph.D in Physics in 1998 at the Institute of High Energy Physics (IHEP) after a visit to the Burst and Transient Source Experient (BATSE) group at NASA/MSFC, where my research was brought to the international level through collaborations, which helped me win the National Excellent Ph.D Thesis Award of China in year 2000. My research on high energy astrophysics was initiated in the pioneer Chinese high energy astrophysics group led by Prof. Tipei Li at the Center for Astroparticle Physics of high energy astrophysics in IHEP, which is the PI group of Hard X-ray Modulation Telescope (HXMT) to be launched probably as the first Chinese astronomical satellite.

Targets of my research in high energy astrophysics:

  • Black hole and neutron star soft X-ray transients 
  • Neutron star low mass X-ray binaries (LMXBs)
  • Accretion-powered, nuclear-powered and rotation-powered millisecond pulsars
  • Gamma-ray bursts and AGNs
Current research interests:
  • Accretion geometry around compact stars
  • The origin of high energy radiation in X-ray binaries
  • Physics of disk-jet interation in microquasars (accreting BHs and NSs)
  • Probes of general relativistic effects using X-ray timing observations
  • The origin of the rapid X-ray variability in X-ray binaries
  • The link between magnetars, rotation-powered millisecond pulsars, and neutron star LMXBs
Selected Research Results:
Selected Publications: