Impact of Accretion Assumptions on Pulse Profile Modelling of Superburst Oscillations in 4U 1636-536

TL;DR

This study uses pulse profile modelling of superburst oscillations in 4U 1636-536 to explore how accretion assumptions affect neutron star property estimates, emphasizing the importance of understanding accretion dynamics.

Contribution

It demonstrates that different accretion assumptions significantly impact inferred neutron star parameters from pulse profile modelling.

Findings

Different assumptions lead to varied mass, radius, and compactness estimates.

Highlighting the importance of understanding accretion rate changes during bursts.

Applying pulse profile modelling to superburst oscillations provides insights into neutron star properties.

Abstract

Modelling the coherent pulsations observed during thermonuclear bursts offers a valuable method to probe the poorly understood equation of state of dense and cold matter. Here we apply the pulse profile modelling technique to the pulsations observed with RXTE during the 2001 superburst of 4U 1636$-$536. By employing a single, uniform-temperature hot spot model with varying size and temperature, along with various assumptions for background/accretion contribution, we find that each assumption leads to different inferred mass, radius, and compactness constraints. This highlights the critical need to better understand the mass accretion rate enhancement/reduction during thermonuclear bursts to accurately model burst oscillation sources using pulse profile modelling.