Tyler Holland-Ashford

Tyler Holland-Ashford

Future Faculty Leaders Postdoctoral Fellow

Center for Astrophysics | Harvard & Smithsonian


My work involves using X-ray observations to study supernova remnants (SNRs). I use spatially resolved imaging and spectral analysis to study the distribution and properties of ejecta in SNRs, along with any compact objects embedded within. I then compare these results to the theoretical predictions of supernova simulations and observational work in other wavelengths in order to learn more about the processes that occur during supernova explosions.

During my time at Ohio State University (graduate student) and the Center for Astrophysics (postdoctoral fellow), I have analyzed data from Chandra, XMM-Newton, ROSAT, and Suzaku X-ray telescopes. In my first projects, I investigated the asymmetries of bulk ejecta in multiple SNRs and specific elements in the SNR Cassiopeia A, performing spectral fitting using the X-ray analysis software Xspec and AtomDB. I quantified the ejecta asymmetries and compared them to each other and NS kick velocity, finding that NSs are preferentially kicked opposite to the bulk of ejecta. In another project, I studied recombining plasma in the SNR W49B, creating spectral fits to 46 regions in the remnant in order to investigate the properties and presence of overionized plasma and constrain the origin of rapid cooling. Most recently, I have performed a detailed analysis of the global X-ray emission in Kepler’s SNR, fitting the entire 0.5-8.0 keV spectrum in order to measure the mass ratios of various ejecta elemenets and link Kepler’s SNR to certain Type Ia progenitor scenarios. In order to obtain accurate results, I incorporated the effects of Suzaku’s effective area calibration uncertainties and the effects of the unknown emitting volumes of different plasma components.

I am currently working on a couple projects. 1.) I am measuring the proper motion of the neutron star in the SNR Cassiopeia A, making use of the wealth of data taken using Chandra from 1999 to present. Even though there are few point sources for which to perform astrometric correction, the sheer number of observations can be used in order to reduce errors and obtain a more precise velocity measurement. 2.) Dr. Adrien Picquenot and myself are using the General Morphological Component Analysis (GMCA) technique to study Kepler’s and Tycho SNRs. We aim to identify the asymmetries of different elements, the plasma properties of different regions of the SNR, and disentangle different types of X-ray emitting material: i.e., swept-up CSM vs Fe-rich vs intermediate-mass ejecta dominant.

In the future, I aim to perform similar global, full-X-Ray-spectrum analysis on other SNRs. I will be able to leverage the knowledge gained and techniques used for my project on Kepler’s SNR to these projects. Additionally, I aim to continue measuring the velocities of NSs embedded in SNRs; these velocities can be compared to the ejecta asymmetries and SNR energetics to help further our knowledge of explosion physics and the mechanism(s) by which NSs are accelerated. Additionally, I will make use of the incredibly detailed spectra from microcalorimeters like XRISM to study the 3D distribution of and make precise measurements of ejecta metals and plasma properties in SNRs.


  • Supernova Remnants
  • X-ray Imaging
  • X-ray Spectroscopy
  • Neutron Star Kicks
  • Supernova Explosion Mechanisms
  • Atomic Data & Modeling


  • PhD in Astronomy, 2021

    The Ohio State University

  • M.S. in Astronomy, 2017

    The Ohio State University

  • B.S. in Physics, 2015

    Harvey Mudd College


Local Environments of Low-redshift Supernovae
Spatially-Resolved Study of Recombining Plasma in W49B Using XMM-Newton
Evidence of a Type Ia Progenitor for Supernova Remnant 3C 397
Asymmetries of Heavy Elements in the Young Supernova Remnant Cassiopeia A
The Age Evolution of the Radio Morphology of Supernova Remnants
Measurement of the Core-collapse Progenitor Mass Distribution of the Small Magellanic Cloud
Comparing Neutron Star Kicks to Supernova Remnant Asymmetries