Prague Synergy 2013: Abstract

Wenda ZhangYu, Wenfei20 min

Low Frequency QPOs in BH and NS XRBs: Frequency Evolution during Transient Outbursts

We studied the evolution of the low frequency quasi-periodic oscillation (LFQPO) component during the rise phase of outbursts of the neutron star soft X-ray transient (SXT) Aql X−1 and the black hole SXT GX 339-4 in the Rossi X-ray Timing Explorer (RXTE) era. The maximum frequency in Aql X-1 is of factor of ~6 higher then that of GX 339-4. This indicates that the maximum LFQPO frequency can be a probe to differentiate black hole SXTs from neutron star SXTs. We studied how the LFQPO frequency evolve with source flux and constrained the truncation disk models which predict the location of the truncation radius under certain mass accretion rate. We measured the rate of change of the LFQPO frequency and constrained viscous torque and the evolution of the Bardeen-Petterson radius, which drive the long time evolution of the LFQPO frequency the in the Lense-Thirring scenarios of LFQPOs. We found that the frequency correlation of the break component and the LFQPO holds down to timescale of ~2 days. Future X-ray missions which can study the correlation on much shorter timescales have the potential to reveal the track on the correlation at shorter timescales.