Soheb Mandhai: Exploring the interplay between compact binaries and their host environments

Thursday 12 Oct 2023, 13:00 → 14:00 Europe/Stockholm

In the era of multi-messenger astronomy including gravitational wave and electromagnetic detections, it is quintessential to formulate strategies that can optimise follow-up campaigns. The electromagnetic counterparts (EMC) of gravitational wave (GW) events arising from the coalescence of two merging compact objects, namely a neutron star paired with another neutron star (NSNS)/black-hole (BHNS), have become increasingly topical over the last few years following the GW170817A. 

In this study, we explore the host galaxy environments and offsets of these binaries (in addition to binary stellar mass black-holes) upon merging. This is accomplished by seeding and dynamically evolving synthetic isolated systems within hydrodynamical galaxies produced by the cosmological simulation, EAGLE. This approach also allows for constraints to be placed on the relative cosmic rate of EM bright binary mergers. Using constraints on the mass ratio of the primary and secondary compact objects, we explore the likelihood of observing potential short-duration gamma-ray bursts (SGRBs) using the Swift/BAT instrument resulting from these systems and compare them to real observations.

The work underlined can be used to formulate strategies to optimise the efforts to search and localise transients (such as SGRBs and their afterglows, kilonovae, and potentially fast radio bursts) to their most likely host galaxies/environment, during the follow-up of LVK observational runs such as the ongoing O4 and beyond. 

We further extend the framework developed to study binaries within the Milky Way (MW). We apply this to a type of binary known as a spidery pulsars :- a cannibalistic system where a low-mass companion is ablated by the primary pulsar. We explore the orbits and dynamics of these systems and their migration within a detailed simulated MW analogue. The aim of this ongoing research is to produce a zoo of binaries, identify the regions within the galaxy that they are likely to occupy, and predict the fraction that will be detectable in the foreground emission of low-frequency gravitational wave detectors such as the DECi-hertz Interferometer Gravitational wave Observatory (DECIGO) and Laser Interferometer Space Antenna (LISA).