Evolution of the quasi-periodic oscillation frequency in GRO J1655-40 – Implications for accretion disk dynamics

Abstract

Context. Low and intermediate frequency quasi-periodic oscillations (QPOs) are thought to be due to oscillations of Comptonizing regions or hot blobs embedded in Keplerian disks. Any movement of these perturbations is expected systematically to change the QPO frequency. Aims. Our goal is to find systems where such a systematic drifts have been observed. We also try to find the real cause of such drifts and whether they shed some light on the accretion disk dynamics. Methods. Using archival data of the recent outburst of GRO J1655-40, we report the presence of such systematic drifts not only during the rising phase from the 25th of February 2005 to the 12th March 2005, when the QPO frequency monotonically increased from 82 mHz to 17.78 Hz but also in the decline phase from the 15th September 2005 to the 5th of October 2005, when the QPO frequency decreased from 13.14 Hz to 34 mHz. Results. We fitted the frequency drifts with the propagatory oscillating shock solution. In the shock-oscillation solution, the frequency is inversely proportional to the infall time scale from the shock location. We obtained the shock location and strength through such a fit. Conclusions. The astonishing smoothness of the variation of the QPO frequency over a period of weeks directly supports the view that it may due to the drift of an oscillating shock rather than the movements of a blob inside a differentially rotating disk.

Accretion flow dynamics during the evolution of timing and spectral properties of GX 339-4 during its 2010–11 outburst

“…The evolution of the low and intermediate QPOs in the outburst sources has been reported quite extensively in the literature (Belloni & Hasinger 1990;Belloni et al 2002a;Belloni et al 2005;Debnath et al 2008Debnath et al , 2012Chakrabarti et al 2005Chakrabarti et al , 2008Chakrabarti et al , 2009. It has been shown for several outburst sources (namely BHs) that the evolution of QPOs can be well-explained by the theoretical propagating oscillatory shock (POS) model (for details, see Chakrabarti et al 2008Chakrabarti et al , 2009Debnath et al , 2012.…”

“…The typical evolution of the QPOs during the outburst phases of the transient black-hole sources has been well-established for a long time (Belloni & Hasinger 1990;Belloni et al 2002a;Belloni et al 2005;Debnath et al 2008Debnath et al , 2012Chakrabarti et al 2005Chakrabarti et al , 2008Chakrabarti et al , 2009). The outbursting BHCs in general show signatures of low and intermediate frequency QPOs during the initial rising phase (mainly low-hard state) as well as in the decline phase of the outburst, where the sub-Keplerian rate dominates and during the intermediate state, where the Keplerian and sub-Keplerian rates are more or less comparable to each other.…”

“…In general, during the rising phase (hard state) of the outburst, the frequency of the QPO increases, whereas during the declining phase, the QPO frequency gradually decreases. These QPO types of evolution (increasing/decreasing nature of QPO frequencies) in these objects can be well-understood due to the propagating oscillatory shocks (POS; Chakrabarti et al 2008Chakrabarti et al , 2009) model. After remaining in the "quiescent" state for almost three years (the last outburst took place during the year 2006/2007, although there is report of weak activity in 2009 as observed by Swift/BAT), GX 339-4 showed X-ray flux activity of 17 mCrab (4-10 keV) on January 03, 2010 with the first detection by MAXI/GSC onboard ISS (Yamaoka et al 2010).…”

Evolution of the temporal and the spectral properties in 2010 and 2011 outbursts of H 1743-322

“…According to POS model in the presence of a shock (Chakrabarti & Manickam, 2000;Chakrabarti et al, 2008), the infall time in the post-shock region is given by,…”

Properties of the propagating shock wave in the accretion flow around GX 339-4 in the 2010 outburst

“…In general, during the rising hard state of the outburst the frequency of the QPO increases, whereas during the declining phase, the QPO frequency is gradually decreased. The QPO evolution in these objects can be well understood through the propagating oscillatory shocks (POS; Chakrabarti et al 2005Chakrabarti et al , 2008Chakrabarti et al , 2009. Though several studies of the evolution of the temporal and spectral states of GX 339-4 during the previous outbursts were carried out (Nowak et al 1999;Belloni et al 2005;Motta et al 2009), the underlying physical processes remained unclear.…”