## Hello there!

I'm Mason Ng, a 5th year Physics PhD Candidate at the MIT Department of Physics and the MIT Kavli Institute for Astrophysics and Space Research.

I use a range of techniques and tools to understand the evolution and dynamics of neutron star binaries!

masonng@mit.edu

I am Wei Chieh Ng (Mason) (personal pronouns: he/him).

I am currently a fifth-year graduate student at MIT's Department of Physics and the Kavli Institute for Astrophysics and Space Research. I mainly work with Professor Deepto Chakrabarty, Dr. Paul Ray, Dr. Ronald Remillard, and Dr. Jack Steiner on X-ray timing and spectroscopic analyses of neutron stars with the NICER data. I also work on X-ray spectropolarimetric observations of neutron stars from the recently launched Imaging X-ray Polarimetry Explorer with Dr. Herman Marshall here at MIT.

This website, like myself, are works in progress. Some of the design elements were inspired by Guðmundur Stefánsson. You can learn more about me and my previous endeavors in the other sections of my website.

## CV

This is my CV from prior to September 2018, though lightly edited to reflect my current position. I leave it here for posterity.

## Current Research

My present work focuses on these areas:

• Understanding the evolution and dynamics of interacting neutron star binaries (through X-ray timing, spectroscopy)

• Developing and maintaining a pipeline for pulsation searches and systematic timing/spectral analysis on archival and incoming NICER data

• Using X-ray polarimetry to understand the magnetic field morphology and accretion geometries of compact objects (with the recently-ish launched Imaging X-ray Polarimetry Explorer)

1 in Nature Astronomy. 1 in Science.

## Presentations

### Talks (* = virtual)

8 (Jan 2023) 241st Meeting of the American Astronomical Society. Seattle, Washington, USA. IXPE Observations of the Pulsar 4U 1626-67.

7 (Dec 2022) Nanyang Technological University Seminar. Singapore. IXPE Observations of the Neutron Star Low-Mass X-ray Binary 4U 1626-67.

6 (Nov 2022) JAXA/ISAS Seminar. Tokyo, Japan. IXPE Observations of the Neutron Star Low-Mass X-ray Binary 4U 1626-67.

5 (Nov 2022) Kyoto University Seminar. Kyoto, Japan. IXPE Observations of the Neutron Star Low-Mass X-ray Binary 4U 1626-67.

4 *(Sep 2022) Astrophysical Polarimetry in the Time-Domain Era. Lecco, Italy. IXPE Observations of the Pulsar 4U 1626-67.

3 (Jul 2022) Committee on Space Research (COSPAR) Assembly 2022. Athens, Greece. IXPE Observations of the Pulsar 4U 1626-67.

2 (Aug 2016; Invited) Auckland Astronomical Society. Auckland, New Zealand. Modelling the spectra of hot stars.

1 (Apr 2016) Royal Astronomical Society of New Zealand Conference. Napier, New Zealand. Modelling the spectra of hot stars.

### Posters

4 (Mar 2023) 20th Divisional Meeting of the High Energy Astrophysics Division. Waikōloa, Hawai'i, USA. Discovery of a 7.8 Hz QPO from the High-Intensity Outburst of Dipping NS LMXB 1A 1744-361.

3 (Mar 2023) 20th Divisional Meeting of the High Energy Astrophysics Division. Waikōloa, Hawai'i, USA. IXPE Observations of the Pulsar 4U 1626-67.

2 (Mar 2022) 19th Divisional Meeting of the High Energy Astrophysics Division. Pittsburgh, Pennsylvania, USA. NICER Pulsation Search and Spectroscopy of the Original Black Widow Pulsar, PSR B1957+20.

1 (Dec 2019) Celebrating 20 Years of Chandra Science Symposium. Boston, Massachusetts, USA. Spectral Evolution of NGC 300 ULX-1.

## Past Research

I previously worked on many facets of astrophysics...

In reverse chronological order,

Investigated the effects of different magnetic field strengths and configurations on the structure of the stellar atmosphere of solar-type stars.

Studied absorber kinematics of 31 OVI absorbers, which exhibited a strong halo mass dependence, where absorbers hosted by L* galaxies have the largest velocity dispersions compared with lower masses and group environments, due to a match between virial temperature and the temperature at which OVI ionization fraction is greatest. Total column densities follow the same behavior, consistent with simulations. Relative absorber--galaxy kinematics of the same sample was studied, though the mass dependence was first normalized out to account for the range of halo masses in the sample. Non-virialized motions due to outflowing gas was observed. Accreting gas signatures were not observed due to multiple line-of-sight structures that were observed, resulting in "kinematic blurring". These results indicate that OVI is not an accurate probe of baryon cycle processes.

There were two projects I carried out:

1) I performed evidence calculations with a trio of codes (CosmoMC, PolyChord, and ModeCode) on several inflationary models, most notable of which is the inflection point inflationary model. Results obtained showed that it is comparable in likelihood to quadratic potentials.

2) I also looked at quantifying the impacts of dark matter on the cosmic microwave background using the 2015 Planck likelihoods, in order to demonstrate the predictive power of dark matter. It was found that dark matter was needed at least at the $10^{100}$ level. While the physical effects of dark matter are well-understood, this quantitative calculation has not been reported in the literature.owave Background.

The results are all summarized in my Senior thesis (US)/Honours thesis (NZ/Aus).

The project involved training a computer to predict image quality from the SkyMapper telescope by considering environmental conditions and telescope configurations. The SkyMapper telescope atop Siding Spring Observatory surveys the entire Southern sky in multiple wavelengths. SkyMapper will inevitably find millions of celestial objects. One result was that the angle of rotation of the CCD camera resulted in visibly lower quality images. Once this was discovered, the SkyMapper team disabled that telescope setting.

Working with Georgie Taylor, we created over 1300 stellar atmosphere models for use in BPASS, the state-of-the-art code incorporating binary stellar systems to predict properties of stellar populations. Results of our work have contributed to the analysis of the recently announced gravitational waves, where it was concluded that similar events are more likely to occur in low-metallicity environments.

I am the Vice-Chair of the MIT Graduate Student Council External Affairs Board (GSC EAB), and am responsible for general programming and maintaining the EAB newsletter (see latest (October 2022) here). The GSC EAB is broadly the external arm of the MIT GSC, advocating on behalf of MIT graduate students in issues of concern to the group (e.g., climate change, research funding). We typically liaise with staffers in Congress and the Biden administration through letters and meetings. We have also sent out statements endorsing certain and relevant legislation (see here.) Most recently, I have led an Astrobites article on the formation of the Graduate Research and Development (GRAD) Caucus in the House of Representatives.

I have co-led the PhysGAAP initiative, where we provide application guidance resources to prospective applicants to reduce the barriers for application to the MIT Physics PhD program, and to address the underrpresentation of students from historically excluded communities. We provide a mentorship program, virtual webinars, as well as a Q&A service. More information can be found here. Please reach out to me if you would like me to speak to your student group about demystifying the graduate school admissions process! This is a free service.

I am also a part of MIT Astrogazers, a group of MIT astrophysics graduate students, who take out telescopes on clear nights to the public and invites them to marvel at bright celestial targets like the Moon, Saturn, and Jupiter (when they are up!)

## Personal History

I come from New Zealand, though my roots stem from Malaysia, where both my parents are from. I have lived in six cities in four countries, over three continents throughout my life!

## Travel

Fun graphic illustrating the countries I have visited thus far! I am always thinking about the next travel adventure!

Create your own visited countries map or check out the JavaScript Charts.