Hello, I am Hsiang-Chih Hwang (黃翔致). I am a postdoc fellow at the Institute for Advanced Study. My research interest covers the formation and the evolution of binary stars, white dwarfs (and their binaries), Milky Way dynamics, active galactic nuclei, binary quasars, and the variability in the sky. I received my Ph.D. degree in astronomy from Johns Hopkins University in 2021. Before I came to JHU in 2016, I got my Bachelor's degree in Physics and Electrical Engineering at National Taiwan University. I am a coffee and milk tea lover. In my spare time, I like hiking, traveling, and playing badminton.
Below is a summary of my education and employment history. Complete CV is available here.
2021 - present
Institute for Advanced Study, Princeton, NJ
Ph.D. in Physics and Astronomy
2016 - 2021
Johns Hopkins University, Baltimore, MD
Thesis advisor: Prof. Nadia Zakamska
Bachelor of Physics & Electrical Engineering
2010 - 2015
National Taiwan University, Taiwan
Advisor: Prof. Chin-Fei Lee
Formation and evolution of binary stars
The age of binaries is notoriously difficult to measure. My research uses stellar kinematics to constrain the age of short-period main-sequence binaries. In Hwang & Zakamska (2020b), we use kinematics as a proxy for stellar age, and show that short-period main-sequence binaries formed with a delay of ~1 Gyr. This delayed formation time supports that these binaries may be formed via magnetic braking.
In Hwang et al. (2020c), we search the wide, comoving companions around contact binaries and hot Jupiter hosts. We found that there is a weak or no enhancement of wide companion fraction for hot Jupiter hosts, and a strong enhancement for contact binaries, providing another clue on the formation of hot Jupiters and contact binaries.
Search for sub-kpc binary quasars
Our VODKA (Varstrometry for Off-nucleus and Dual sub-Kpc AGN) team is developing a new way to detect sub-kpc dual AGN and off-nucleus AGN using varstrometry. Varstrometry is a combination of variability and astrometry: with high-precision astrometry, we aim to detect the astrometric jitter caused by the unresolved, variable double-core (or offset) sources. Our exploration of varstrometry in Gaia DR2 is present in Hwang et al. (2020a), and its implication for off-nucleus AGN is present in Shen, Hwang et al. (2019). Our Hubble Space Telescope program (PI:Hwang) follows up these astrometry-selected candidates, and the results show that this new method can find binary quasars efficiently (Chen, Hwang, et al. (submitted))!
White dwarfs play a critical role in astronomy because they are the progenitors of type Ia supernovae, which have been used to measure the accelerated expansion of the Universe. Led by Vedant Chandra, a senior at JHU (now a graduate student at Harvard), we have developed machine-learning-based tools wdtools for spectroscopic analysis of white dwarf spectra (Chandra, Hwang et al. (2020a)). Furthermore, we used these tools to measure the mass-radius relation of white dwarfs using gravitational redshifts over a large mass range for the first time Chandra, Hwang et al. (2020b)! This work has been featured in JHU press release and Science News. More excitingly, we recently discovered a double-white-dwarf binary with an orbital period of 99 minutes (Chandra, Hwang et al. 2021)!
You can find me via email most effectively!
Bloomberg Hall 143