Predoc List

Aafaque Khan
Aafaque Khan, High Energy Astrophysics
University of Arizona
Advisor: Patrick Slane

Aafaque is a graduate student at the Steward Observatory, University of Arizona. His research with Dr. Erika Hamden focusses on leveraging recent innovations in Ultraviolet technology for application in space based instruments to study the Circumgalactic medium (CGM) and the Interstellar medium (ISM) and the role they play in galaxy evolution. His research also takes a deep dive into end-to-end design, development and calibration of UV space and balloon borne instruments through participation in NASA funded Stratospheric Balloon borne Faint Intergalactic Red-shifted Emission Balloon-2 (FIREBall-2) Multi-object Spectrograph (MOS), and Aspera UV Smallsat, a NASA Astrophysics Pioneers mission. Aafaque is the lead of the calibration working group for the Aspera mission. At the CfA, Aafaque will work with Dr. Patrick Slane, to develop a detailed understanding of mission design, on-board calibration and the scientific operations of UV Astrophysics missions. He will take the lessons learned from discussions with space instrumentation experts at SAO and apply them in developing the on-board calibration of Aspera. During his visits to SAO, he will be using archival data from the FUSE mission and combine them with the Aspera’s throughput and noise models to develop the flux and wavelength calibration pipeline.

Won Ki Lee, High Energy Astrophysics
Advisor: John ZuHone

Wonki is a Ph.D. student at Yonsei University where he pursues research on radio relics with Prof. M. James Jee. Radio relics are Mpc-size diffuse radio emissions found in the outskirts of colliding galaxy clusters and are now believed to trace the cluster merger shock. Wonki has used numerical simulations and multi-wavelength observations to understand the formation history of the observed radio relics and demonstrated that radio relics provide powerful tools when we constrain the collision history. At CfA, he will perform magnetohydrodynamics simulations under the supervision of Dr. John ZuHone to test an alternative formation scenario of radio relics and to evaluate the model with observations, which will reassess the role of radio relics in predicting the collision history.

Benjamin Roulston
Benjamin Roulston, High Energy Astrophysics
Advisor: Paul Green

Benjamin is a PhD student at Boston University under the supervision of JJ Hermes. Ben's work at the CfA focuses on studying stellar variability with the Time Domain Spectroscopic Survey (TDSS) in the SDSS-IV. One project involves measuring radial velocity variability of dwarf carbon (dC) stars and using MCMC methods to fit separation distributions and constrain the binary fraction of these peculiar stars. While another project focuses on using the large sample of variable (periodic and non-periodic) stars in TDSS that have both light curves and spectra to provide spectral characterization of stellar variables. The ultimate goal is to develop a machine learning tool that uses both light curves and spectra to classify variable stars.

Soumya Roy
Soumya Roy, High Energy Astrophysics
Advisor: Katharine Reeves

Soumya is a graduate student from the Inter-University Centre for Astronomy and Astrophysics (IUCAA), working with Professor Durgesh Tripathi. He is interested in studying the energy distribution of Solar flares and their direct and indirect effects on the local plasma environment. He is also a part of the Solar Ultraviolet Imaging Telescope (SUIT) team, one of the payloads onboard the upcoming Aditya-L1 Solar mission designed and developed Indian Space Research Organization (ISRO). He is working to characterize the imaging performance of SUIT and various components of the pipeline. At the CfA, Soumya is working with Dr Katharine Reeves to determine the thermal energy content and evolution in solar flares. He is coordinating with other team members to understand how thermal energy contributes to the global energy budget of the events. The bulk thermal energy of the flares will be obtained from the Hinode X-ray telescope and the Atmospheric Imaging Assembly on the Solar Dynamics Observatory through the use of differential emission measure technique, along with hard X-ray data from the Fermi satellite to gain an understanding of the non-thermal energy evolution. Studying the thermal and non-thermal energy partition and their evolution would help us understand the evolution of the global energy budget and the energy partitioning in solar eruptive events from the chromosphere to the inner heliosphere.

Arnab Sarkar, High Energy Astrophysics
Advisor: Scott Randall

I am a Ph.D. student at the University of Kentucky working under the advisory of Dr. Yuanyuan Su. I mainly study the intracluster medium (ICM) properties in the galaxy cluster outskirts, where the ICM connects to the large-scale cosmic web. In the standard CDM cosmological structure formation model, galaxy clusters continue to grow and evolve through mergers and the accretion of matter, mainly along cosmic filaments, in their outer regions. Therefore, probing the outskirts of galaxy clusters is crucial to study cosmology and the growth of large-scale structures. Here at CfA, under Dr. Scott Randall's supervision, I look for correlations between global cluster properties and sub-self-similar entropy values (SSSEV) in the cluster outskirts, which will provide a better understanding of how SSSEV varies with cluster mass and dynamical state.

Crisel Suarez
Crisel Suarez Bustamante, High Energy Astrophysics
Advisor: Christopher Moore

Crisel Suarez is a graduate student at Vanderbilt University where she is currently pursuing her Ph.D in Physics. She is interested in studying the physical properties of the solar corona by comparing different types of observations to numerical models. Her research focuses on analyzing solar flare observations from the Miniature X-ray Solar Spectrometer (MinXSS) Cubesats and using the hydrodynamic numerical simulations (HYDRAD) to better understand the emission, temperature and elemental abundances of the solar corona during flares. While at the CfA, Crisel is working with Dr. Christopher Moore to better understand the signature of Quasi-Periodic Pulsations (QPP) in solar flares by using a data constrained successive reconnection model.

Santiago Ubach Ramirez, High Energy Astrophysics
Advisor: James Steiner

Santi is a PhD student at Autonomous University of Barcelona (UAB) under the supervision of Dr. Gaug and Dr. Font in the high energy astrophysics group. Specially, Santi is focused on the detection of Quasi-Periodic Oscillations (QPOs) in the Very High Energy (VHE) regime inside the MAGIC collaboration to try to understand the origin of these QPOs. Such QPOs appear in stellar-mass Black Hole Binary (BHB) systems but also in Active Galactic Nucleus (AGN). At CfA and under the supervision of Dr. James Steiner, will study the Dynamic Accretion onto Stellar-Mass Black Holes, measuring the spin of black hole systems, modeling QPOs in black hole systems and relating QPO changes to spectral evolution of the BH system, modeling the geometrical and spectral characteristics during a black hole outburst, and using the premier Magellan telescopes to measure orbital characteristics and determine the masses of quiescent black hole systems. Outside of research, he enjoys reading science fiction and training for an Ironman, watching Japanese animations, and working as a field hockey coach. You can also find him playing field hockey or working extra hours.

Yang Yang
Yang Yang, High Energy Astrophysics
Advisor: Amy Gall

Yang Yang is a Ph.D. student from Clemson University, working under the supervision of Dr. Endre Takacs in atomic physics and laboratory astrophysics, an area of physics that reproduces extreme physical environments that can be found in different astrophysical objects. These environments can be simulated in devices called electron beam ion traps (EBIT) by observing the radiation emitted in the interaction of highly ionized atoms with high-energy electrons. Yang had prior experience with electron beam ion traps at the National Institute of Standards and Technology (NIST) in Gaithersburg. Now she is working under the advisory of Dr. Amy Gall, operating SAO EBIT. Their work provides laboratory astrophysics atomic data for AtomDB, the database maintained by Dr. Adam Foster and Dr. Randall Smith to provide critical data for the analysis of astrophysical spectra.