Hao-Jui Kuan (官顥叡)

I am doing my first postdoc at the Max Planck Institute for Gravitational Physics, where I mainly study phenomena manifesting in binary neutron star mergers.

About me

I come from Hsinchu -- a county in the North Taiwan, where I spent my young ages and completed my Bachelor degree with double majors in Physics and Mathemactics. Following my academic training at the BCs level, I joined the group of Prof. Chao-Qiang Geng in Hsinchu as a PhD student. Two years later in 2019, I opted to seek a joint PhD degree between Nat'l Tsing Hua Uni. (Taiwan) and Uni. of Tübingen (Germany), and entered Prof. Kostas Kokkotas' group in Tübingen. I defended my thesis at the very end of 2022, and gained the degree in early 2023. I am now affiliated at the Albert Eintein Institute in Golm with Prof. Masaru Shibata as the mentor.

Research

1. Precursor flares of short gamma-ray bursts

There are a few percursor flares detected for SGRBs, which may be related to the tidal activities in the pre-merger stage of coalescing binaries with neutron star; tidal force pushes the star at a specific frequence double the orbital one. As the binary coalescing, the pushing frequency will unavoidably approach the vibration rate of certain stellar oscillation mode, rendering a resonance. The efficiently excited oscillation then exerts stress on the crust, which can be strong enough to yield the crust in some situation. Matching the time of the occurence of precursors provides the information about modes' frequencies, and thus certain properties of the star can be reckoned in an asteroseismology manner. We aim to explore possible implication of such on, e.g., nuclear equation of state and the spin of the star exhibiting the flares.

2. Waveforms of binary neutron stars in Einstein's theory and beyond

Gravitational waves are arguably the most ``pure'' emission of coalescing binary neutron stars, compared to electromagnetic and neutrino radiations where certainties can be huge. These spacetime ripples undulate at frequencies that are related to orbital motion with amplitude that are associated with curvature built by the system. In addition, the evolution of their freuqency is sensitive to the dynamics in this one-of-the-most violent processes in the Universy. Having accurate knowledge of the gravitational physics in strong gravity regime is almost equivalent to having accurate waveform modeling. We particularly look at the late-time contributions to the waveform, such as tidal response of neutron stars in both general relativity (GR) and modified gravity (MG). Contributions excusive to MG are also investigated, which can unambiguously suggest the necessity of going beyond GR once confirmed.

Published Paper

2020-2021 2022-2023

CV

Detailed CV