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Colloquium

Oscillations in the inner region of optically thick accretion disk in Z-type neutron star sources

2019-03-29
  • Speaker : Prof. K. Sriram (Osmania Univ., India)
  • Date : 2019-06-12 16:00 ~ 17:00
  • Location : JYS 331-2
  • Host : Dr. Chul-Sung Choi

A unique QPO often occurs at 6 Hz in Z type Neutron star sources radiating close to the Eddington limit. From radio observations, it is known that a jet is present during the 6 Hz QPO and sometimes ultra relativistic flow is also associated. In general these sources the QPO varies from ~20-50 Hz during which the inner region of accretion disk is truncated and a Compton cloud/corona is present inside the truncation radius. As the truncated front approaches close to the last stable orbit (50 Hz), suddenly a unique 6 Hz QPO appears. I will discuss a model which probably explains the sudden emergence of the 6 Hz QPO along with 50 Hz QPO. In this model, I study the disk oscillation during which the inner region of the disk dominated by radiation pressure assuming that the oscillation is driven by the gravitational force. I will also use this model explain the sudden occurrence of type-B/A QPOs in black hole X-ray binaries which are similar to the 6 Hz QPO in neutron star source.