Correlating the non-linear time series and spectral properties of IGR J17091–3624: is it similar to GRS 1915+105?

Abstract

ABSTRACT Using the correlation integral method, we explore the non-linear properties of IGR J17091–3624 by comparing the underlying behaviour to GRS 1915+105. We find that while GRS 1915+105 is known to reveal a combination of fractal (or even chaotic) and stochastic behaviours depending on its temporal class, IGR J17091–3624 mostly shows stochastic behaviour. Therefore, although several observations find that IGR J17091–3624 is similar to GRS 1915+105, and that they have temporal classes in common, the underlying non-linear time series analyses offer a different view. Nevertheless, the ratio of the Poisson noise to rms variation for IGR J17091–3624 turns out to be high, suggesting that it is dominated by Poisson noise. Hence it might plausibly lead to the suppression of its non-linear properties, if there is any. Indeed, IGR J17091–3624 is a very faint source compared with GRS 1915+105. However, by increasing the time bin, some of the temporal classes of IGR J17091–3624 show deviation from stochasticity, indicating the plausibility of a higher fractal dimension. Along with spectral analysis, overall IGR J17091–3624 seems to reveal three different accretion classes: slim, Keplerian and advective accretion discs.