Educational History
- Ph.D. University of Oklahoma, 2022
- M.S. University of Oklahoma, 2018
- B.A. North Central College, 2015
Hello I'm James DerKacy, a postdoctoral researcher at Space Telescope Science Institute. As a supernova spectroscopist and phenomenologist, I use both observational (HST, JWST) and theoretical (SYNOW, PHOENIX) tools to study the physics of supernovae; with a particular focus on understanding the progenitors and explosion mechanisms which drive their diversity.
A listing of all works I've written or contributed to can be found here.
As part of the Mid-InfraRed SuperNovA Collaboration (MIRSNAC), I study the nebular phases of supernovae using the James Webb Space Telescope (JWST). At these phases, the entire ejecta is optically thin, allowing us to probe the inner-most regions where explosion models predict the greatest differences will be found. Using JWST observations of both SNe 2021aefx and 2022xkq, I've led papers demonstrating both normal-luminosity and under-luminous SNe Ia likely arise from near-Chandrasekhar mass white dwarfs. I also lead a multi-cycle JWST program to obtain ultra-late phase spectra of SN 2021aefx to further study the evolution of SN Ia spectra in the infrared.
Ultraviolet spectra of supernovae are a unique and understudied resource for determining the origins of these cosmic explosions. In the ultraviolet, the photsphere recedes slower than in the optical and infrared, making the outermost layers accessible beyond the first few days after explosion. In Type Ia supernova, the elements present in these layers will differ depending on which mechanism caused the explosion. Using the complete UV spectral sample taken with the Hubble Space Telescope, I'm leading efforts to understand the complicated mechanisms which form the UV spectra in SNe Ia and how these HST spectra can be used to constrain the explosion mechanisms.
An alumnus of the SN Numerical Radiative Transfer Group (SNNRTG), I utilize the PHOENIX code to simulate full NLTE spectra of a variety of supernovae for comparison to observational data. My current focus is generating spectra to explain the diversity of Type Ia SNe; focusing on the ultraviolet and the root causes of the differences in optical spectra between the different Branch subgroups. I've also investigated the spectral signatures of different power sources in super-luminous supernovae (SLSNe), such as circumstellar interaction or magnetic braking of a magnetar; as their high luminosities cannot currently be explained by traditional models.
Much of our current knowledge about supernova explosions comes from follow-up observations in the weeks and months after explosion. However, information about the early stages of the explosion and the nearby environment is lost after the first few hours and days. The Precision Observations of Infant Supernova Explosions (POISE) collaboration is actively working to obtain rapid cadence, multi-wavelength photometry and spectroscopy as close to explosion as possible to answer many outstanding questions about supernova progenitors through detailed studies of the outer ejecta and the surrouding environment. With this data, we can estimate key explosion parameters and distinguish between leading explosion models of all types of supernovae.
As an undergraduate, I interned at Argonne National Laboratory under the supervision of Steve Kuhlmann through the SULI program, working primarily to assist in the development of silicon photonics for use as atmospheric OH filters. I also provided assistance to the Dark Energy Survey (DES) Supernova group at Argonne, including analysis of supernova light curves and identifying targets for spectroscopic follow-up. Information on the silicon photonics project can be found here and information on DES and its mission are located here.
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