People

"The hardest problems of pure and applied science can only be solved by the open collaboration of the world-wide scientific community."

-Kenneth G. Wilson, Nobel laureate and Caltech alumnus

Our Faculty

Prof. Fiona Harrison

NuSTAR and UVEX PI

Prof. Fiona Harrison is the California Institute of Technology (Caltech) Benjamin M. Rosen Professor of Physics, and the Kent and Joyce Kresa Leadership Chair of the Division of Physics, Mathematics and Astronomy. Prof. Harrison’s research is focused on the study of energetic phenomena ranging from gamma-ray bursts, black holes on all mass scales, to neutron stars and supernovae. Currently she is principal investigator for NASA’s Nuclear Spectroscopic Telescope Array (NuSTAR). She received her Ph.D. in physics from the University of California, Berkeley, and went to Caltech in 1993 as a Robert A. Millikan Prize Fellow in Experimental Physics.

  • fiona[at]srl[dot]caltech[dot]edu

Technical and Administrative Staff

Dr. Murray Brightman (he/him)

Staff Scientist

I am a staff scientist at the NuSTAR Science Operations Center, part of the team that operates and maintains the NuSTAR telescope. My current research interest is in X-ray transients. These are sources of X-rays that come and go that could be black holes or neutron stars undergoing a brief period of accretion, the merger of two neutron stars, supernovae, or flares from stars in our Galaxy.

  • murray[at]srl[dot]caltech[dot]edu
Dr. Hannah Earnshaw (they/them)

NuSTAR Project Scientist

Hannah's primary research interest is in ultraluminous X-ray sources and other accreting X-ray binaries in nearby galaxies. They are also part of the team responsible for calibration and upkeep of the NuSTAR telescope.

  • hpearn[at]caltech[dot]edu
Dr. Karl Forster

Manager, NuSTAR Science Operations Center

Karl supervises the operation of the NuSTAR space telescope, ensuring that scientists around the world obtain the observations requested for their investigations, often leading coordination with other telescopes in space and on the ground.

  • krl[at]srl[dot]caltech[dot]edu
Dr. Brian Grefenstette (he/him)

Research Scientist

Brian works on hardware and mission development as well high energy astronomy. He is one of the principal mission scientists for NuSTAR and leads the calibration efforts. He is also the payload manager for the Ultraviolet Explorer (UVEX) NASA MIDEX responsible for delivering the wide-field UV telescope and its cameras. He uses telescopes to study a wide range of astrophysical phenomena, from the leftover remnants of exploding stars to flares from the Sun and high energy emission from X-ray binaries.

  • bwgref[at]srl[dot]caltech[dot]edu
Dr. Hiromasa Miyasaka

Senior Staff Scientist

I am a detector scientist for NuSTAR CZT detector as well as many other radiation detectors. I have been studying CZT/CdTe solid-state pixel detectors for NASA’s future high-energy X-ray missions as part of an APRA program. I have also participate to develop the particles detector for NASA’s STEREO and Parker Solar Probe mission. I am currently working on to develop the detector readout system for the SPHEREx mission.

  • miyasaka[at]srl[dot]caltech[dot]edu
Dr. Soudabeh Mashhadi

Research Scientist and Instruments System Engineer

I am a solid-state physicist working on the UVEX mission. My role encompasses detector related fabrications and characterization setups development.

  • mashhadi[at]caltech[dot]edu
Dr. Daniel Stern (he/him)

NuSTAR Deputy PI

I primarily study extreme supermassive black holes at a variety of wavelengths, including very distant ones, heavily enshrouded ones, and ones that are rapidly changing in brightness.

  • daniel[dot]k[dot]stern[at]gmail[dot]com

Our Postdocs

Dr. Oluwashina (Shina) Adegoke

Postdoctoral Research Associate

I analyze X-ray data to investigate the connection between spectral states and the geometry of accretion flows in black hole X-ray binaries (BHXBs) during outbursts, with a particular focus on the influence of mass accretion rate on this relationship. My research also explores the physics of outflows, disk winds, and obscuration commonly observed in highly inclined BHXBs, which are often transient or state-dependent phenomena. Additionally, I am deeply interested in the multi-wavelength variability characteristics of active galactic nuclei (AGN).

  • oadegoke[at]caltech[dot]edu
Dr. Peter Boorman (he/him)

Postdoctoral Research Associate

I study the structure and evolution of the environment surrounding growing supermassive black holes with broadband X-ray spectral analysis and multi-wavelength observations. This includes finding and classifying black holes that grow behind thick layers of obscuring material, as well as analysing the growth of black holes across a broad range of mass, luminosity and accretion rate. I'm also interested in new ways to analyse astrophysical data including parameter exploration and data visualisation.

  • boorman[at]caltech[dot]edu
Dr. Elias Kammoun

Postdoctoral Research Associate

I am a black hole astronomer. I study how black holes grow, evolve, and shape the universe. My focus is on the supermassive ones that power the centers of active galaxies. I investigate their behavior, ranging from the innermost regions - exceptional laboratories for studying gravity at its glory - to the more extended regions where black holes inject power and matter into their host galaxies, altering their evolution. In my research, I combine observational and modeling techniques to understand the multi-wavelength spectral and timing properties of black holes.

  • ekammoun[at]caltech[dot]edu
Dr. Demet Kirmizibayrak

Postdoctoral Research Associate

My main focus of research is compact objects, particularly black holes and neutron stars. I enjoy working with observations and theory, aiming to bridge the two to deepen our understanding of physics and the universe. Some particular areas I am passionate about are: accretion physics, AGN and black hole variability, multi-wavelength astronomy, jets, magnetars, and studying compact objects and transient phenomena through spectral-timing analysis, imaging and polarimetry. Most of the time I am working on developing novel timing methodologies for astronomy and applying them on accreting black holes to study time lags and variability. When I’m not doing that, I’m working on spectropolarimetry and imaging of supernova remnants, magnetars and X-ray binaries, or running simulations for upcoming high time/spectral /spatial resolution and high effective area missions, exploring their applications to physics and instrumentation design.

  • demet[at]caltech[dot]edu
Dr. Lea Marcotulli (she/her)

Visiting Postdoctoral Fellow

I am a high-energy astrophysicist and my main research focus is chasing supermassive black holes at the dawn of the Universe that power relativistic jets. I use both NASA satellites in space that explore the universe at the highest X- and gamma-ray energies, as well ground-based infrared and optical facilities, to find and study the most powerful, most distant of these sources. Among the questions I am trying to answer: how did these black grow so big so early on? How did they evolve, from then to us? What is the process of triggering these extreme relativistic jets from their cores?

  • lea[dot]marcotulli[at]yale[dot]edu
Dr. Joanna Piotrowska (she/her)

Postdoctoral Research Associate

Coming from a PhD background in galaxy evolution in optical observations and cosmological simulations, I joined Caltech to study the central engines in massive galaxies - their Active Galactic Nuclei in X-ray, optical and UV wavelengths. In my research I combine conventional statistical methods with machine learning to extract information otherwise not captured from the data with standard analysis techniques. Apart from galaxies and supermassive black holes I am also interested in the development of numerical methods, in particular (pseudo-) spectral schemes applied to discontinuous problems, e.g. shock discontinuities in fluids.

  • joannapk[at]caltech[dot]edu
Dr. Aaron Tohuvavohu

Troesh Postdoctoral Scholar Research Associate in Physics

My research focuses on multi-messenger astrophysics (with light across the spectrum, gravitational waves, and occasionally neutrinos), and relativistic explosions. Generally I am interested in using astrophysical phenomena to probe physics that is otherwise inaccessible to terrestrial laboratories. I focus much of my time developing new space telescopes and experiments targeted at compelling astrophysical mysteries, as well as novel data analysis techniques and control systems to enhance the capabilities of existing instruments.

  • tohuvavo[at]caltech[dot]edu

Our Graduate Students

Yuanze Ding

Graduate Student

Black hole, neutron star…I am interested in the most powerful objects in the Universe. I have been working on X-ray binary and Active Galactic Nucleus (AGN) with X-ray satellites since I was an undergrad. My current research includes both theoretical and observational work, like modeling accretion disk reflection and studying AGN-Galaxy co-evolution with X-ray telescopes.

  • yding[dot]caltech[dot]edu

Our 2025 Summer Students

Vincent Caudillo

SURF Student

I am a rising senior at UCI, double-majoring in Physics and Math. Most of my work at UCI has been in cosmology and astroparticle physics, with a focus on dark matter and galaxy evolution. I have also worked on some projects within plasma and condensed matter physics. This summer will be all about changing-look active galactic nuclei. I enjoy hanging out with friends and family, combat sports, and playing video games.

  • caudillv[at]uci[dot]edu
Cyrus Clabeaux

SURF Student

I am a rising sophomore at Stony Brook University majoring in Physics and Applied Mathematics and Statistics. This summer I am excited to apply data analysis techniques to explore the properties of black hole X-ray binary accretion and outburst. Previously, I have worked on projects involving biophysics and particle physics. Some of my hobbies include badminton, basketball, tennis, swimming, ice skating, piano, viola, drawing/painting, video games, and movies/TV series.

  • cyrus[dot]clabeaux[at]stonybrook[dot]edu
Indie Desiderio-Sloane

SURF Student

I am a rising-junior at Caltech. I am interested in physics. I am really excited to continue my research project with Asia for another summer! Previously, I have completed and published research about Spurious Solar-Wind Effects on Acceleration Noise in LISA Pathfinder with Dr. Grant Meadors of LANL and Arnold Yang. In my free time, I enjoy reading, baking, and spending time with and competing with my horse, Emmy.

  • idesider[at]caltech[dot]edu
Kenji Farrell

SURF Student

I’m a rising sophomore at Caltech majoring in Physics, with particular interests in general relativity and cosmology. Outside the classroom, I’m a pitcher on Caltech’s baseball team and enjoy playing tennis and chess in my free time. I’ve also been a part of Caltech’s Quizbowl team and hope to compete in some tournaments with the team over the summer.

  • kfarrell[at]caltech[dot]edu
Yifan Hu

SURF Student

I’m a rising third-year physics student at Imperial College London, focusing on high-energy astrophysics and time-domain observations. I’ve previously worked with the Einstein Probe group at the Chinese Academy of Sciences on stellar flare characterisation, and I’m currently collaborating with the European Space Agency on flare energy scaling laws across different wavelengths. This summer at Caltech, I’m analysing NuSTAR hard X-ray data to investigate how both soft and hard X-rays contribute to atmospheric escape in M-dwarf exoplanet systems. Outside of research, I enjoy deep-dive reading, and collecting space mission memorabilia.

  • yh3123[at]ic[dot]ac[dot]uk
Julian (Juju) Jackson

SURF Student

I’m currently a rising junior at the University of California majoring in Astronomy and Astrophysics with a minor in African American Studies. Some of my previous projects have been in Particle physics exploring the intricacies of the Top Quark at UCSD and Gamma Ray Burst/Black Hole research at Los Alamos National Laboratory. My goal is to work at NASA (JPL) after obtaining my PhD and do extensive research on black holes or dark matter! Later in my career, I also aim to be a lead scientist for a telescope and possibly teach at a university! Other hobbies I have are stargazing/Astrophotography, playing basketball, reading (Dystopian), playing video games and just going on adventures with friends. Lastly, a fun fact about myself is that I have my own TEDx Talk on Youtube about my journey. 🙂.

  • juj002[at]ucsd[dot]edu
Robert J. Mailliard (he/him/his)

SURF Student

I am a rising fourth-year astronomy and astrophysics student at Indiana University Bloomington with minors in mathematics and theatre and drama. I have research interests in many fields, especially heliophysics, galaxy evolution, black holes, and cosmology. Outside the classroom, I am active in astronomy outreach and public education, as well as the LGBTQIA+ community. I love to write music, perform/see musical theatre, and mini golf.

  • robertjmailliard[at]gmail[dot]com
Sophia Nicolella

SURF Student

I am a rising senior at UT Austin double-majoring in astronomy and physics! At UT, I work in the Center for Gravitational Physics studying gravitational waves. This summer, I am working with Hannah studying ultraluminous X-ray binaries! I love to read, draw, paint, and play the piano in my free time.

  • sophia[dot]nicolella[at]utexas[dot]edu
Yabo Ogunduyile

SURF Student

I am a rising 4th year student at Cal State LA double majoring in Physics (focus in astronomy) and Mechanical Engineering. On campus I do research with my advisor Dr. Margaret Lazzarini using Multi-wavelength Observations to Identify High Mass X-Ray Binary systems in nearby galaxies. I am interested in pursuing a PhD in Astrophysics focusing on high-energy astrophysics, galaxy and stellar evolution and black holes. Some of my hobbies include watching action/comedy/sci-fi movies, reading dystopian/mystery books, singing (in private). I also enjoy hiking, swimming, eating good food, and watching art.

  • yogundu2[at]calstatela[dot]edu