Speaker
Description
Extracting nonlinear nature of astrophysical systems, particularly
from observed data, has long been considering for various kinds of sources.
Accretion disks around compact objects are one of them. Our group
has been working on it for more than two decades: for GRS 1915+105,
Sco X-1, Cyg X-1,2,3, IGR J17091–3624, etc. Sources exhibit sometimes
chaotic/deterministic and sometimes stochastic nature. Interestingly,
GRS 1915+105, depending on its temporal class, exhibits both.
IGR J17091–3624, on the other hand, has been argued to be twin of
GRS 1915+105 due to their similar ``heartbeat" pattern in lightcurves
and high-frequency QPOs, for quite sometime. However, the former
is a very faint noise-dominated source, exhibited stochastic nature
in timeseries by earlier studies, which further challenged its twin
status of GRS 1915+105. We employ several denoising techniques to mitigate
noise effects and employ methods like Autoencoder, Principal Component
Analysis (PCA), Singular Value Decomposition (SVD), and Correlation Integral
(CI) to isolate the deterministic signatures. We find signs of determinism
in IGR J17091–3624 after denoising, thus supporting the hypothesis of it
being similar to GRS 1915+105, even as a dynamical system. Our findings not
only shed light on the complex nature of IGR J17091-3624, but also pave the
way for future research employing noise-reduction techniques to analyze
non-linearity in observed dynamical systems.
