Research Projects

The study of GWs, first directly detected by LIGO in 2015, has opened a new window into the cosmos and greatly expanded our understanding of compact object binaries. These detections offered new ways to explore the predictions of Einstein's General Theory of Relativity (GTR). Among various GW sources, extreme and intermediate mass ratio inspirals (E/IMRIs)—where a stellar-mass compact object (10–10³ M⊙) orbits a supermassive black hole (SMBH) (10⁵–10⁸ M⊙)—are prime targets for space-based detectors like LISA. E/IMRIs are of exceptional interest because they allow us to probe the strong-field regime of GTR, where the field is immensely strong and deviations from classical physics are most pronounced. To extract information from these sources, the emitted gravitational waveform must be modeled with extreme accuracy. This modeling requires a detailed understanding of the dynamics of the orbiting compact object, which, in the case of E/IMRIs in AGN, is strongly influenced by the presence of other gravitating objects in AGN. The compact object's dynamics are shaped by the combined effects of the central SMBH, accretion disc, & dark matter. These exert hydrodynamic drag on the orbiting object, modifying its trajectory and, consequently, the emitted GW signal. This interaction introduces a characteristic signature in the GW. Given the expected sensitivity of LISA to low-frequency GW signals, it is crucial to develop theoretical models that accurately describe the influence of all the significant gravitating components of AGN on the GW emission from E/IMRIs. These effects complicates the waveform modeling and may introduce errors in the estimation of BH parameters of companions. This proposal aims to address this issue by predicting the specific signatures particularly of accretion discs and dark matter distribution on the GW signals from these systems. By analyzing the infall time variations and phase shifts, we aim to identify the detectability of these effects in the GW signal and determine the changes in the GW signal's amplitude and frequency. Furthermore, we will explore the impact of different accretion disc models and different dark matter model on the orbital evolution of compact objects. The detectability of these influences depends on the chosen hydrodynamic model of accretion disc, different dark matter density distribution compact object, and the sensitivity of GW detectors. This research will have implications for the study of EMRI dynamics, the population and distribution of compact objects in galactic nuclei, dark matter detection, identifying the accretion disc model and the testing of alternative theories of gravity. More importantly the major impact of the project is understanding the GW signals that LISA will observe, as these signals are sensitive probes of the environment around SMBHs.