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

Dr. Fiona Harrison

Dr. 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. Dr. 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
Dr. Javier Garcia (he/him)

Research Assistant Professor of Physics

I build models using radiative transfer, general relativity, and laboratory astrophysics to simulate the X-rays reflected from accretion disks around black holes and neutron stars.

  • javier[at]caltech[dot]edu

Technical and Administrative Staff

Dr. Matteo Bachetti (he/him)

Staff Scientist

During music classes, I was bad at rhythm, so I built a career around it. Today, I measure the rhythm of neutron stars and black holes, with techniques collectively called "timing analysis".

  • matteo[dot]bachetti[at]inaf[dot]it
Dr. Murray Brightman (he/him)

Staff Scientist

I am a staff scientist at the NuSTAR Science Operations Center. My duties include generating and delivering the pointing commands to the spacecraft, archiving and cataloging observational data, and calibration. My research interests include X-ray transients, ultraluminous X-ray sources, and heavily obscured active galactic nuclei.

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

Staff 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

I am one of the principle mission scientists for NuSTAR and lead the NuSTAR calibration efforts. I use NuSTAR and other X-ray 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
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. Daniel Stern (he/him)

NuSTAR Project Scientist

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. McKinley Brumback (she/her)

Postdoctoral Research Associate

I do X-ray spectral and timing studies of accreting pulsars. I am interested in the way gas interacts with the extreme magnetic and gravitational fields surrounding the neutron star.

  • mckinley[at]caltech[dot]edu
Dr. Thomas Connor (he/him)

NASA Postdoctoral Program Fellow

I study the first black holes to form in the Universe, which have grown to over a billion times the mass of the Sun within a few hundred million years after the Big Bang. I utilize X-ray observations to identify the evidence of possible mechanisms that could enable such a rapid growth. I also conduct ground-based observations to try to identify new black holes in this early epoch.

Dr. Riley Connors

Postdoctoral Research Associate

I am interested in all things black holes, in particular stellar mass black holes in binary orbit with another star. I model spectral data provided to us by modern X-ray telescopes (and sometimes in other wavelengths) in order to study the nature of black holes. My current focus is on relativistic reflection, whereby X-rays emitting by the hot gas around black holes shine on the spiraling accretion disk, leaving an imprint of the strong gravitational force of the black hole. My goal is to discover how rapidly these black holes spin, giving us a better insight into how they formed in the first place.

  • rconnors[at]caltech[dot]edu
Dr. Jérôme Deprince

Postdoctoral Research Associate

"Born" as an atomic physicist, my PhD thesis was about the study of high-density plasma environment effects on the atomic parameters involved in iron K-line X-ray emission by accreting black holes. Now, since these new atomic data have been implemented in the X-ray astrophysical modeling code XSTAR, my purpose is to estimate how these changes in atomic data can affect the X-ray spectra emitted by such astrophysical objets (and even other ones).

  • deprince[at]caltech[dot]edu
Dr. Amruta Jaodand (she/her)

Postdoctoral Research Associate

I study neutron stars using multi-wavelength observations to understand their evolution and interactions with other stars in compact binaries.

  • ajaodand[at]caltech[dot]edu
Dr. Nikita Kamraj

Postdoctoral Research Associate

I work on studying Active Galactic Nuclei (AGNs) in our local universe using broadband X-ray spectroscopic techniques. In particular, I study fundamental properties of the corona in AGNs, which is responsible for producing the luminous X-ray continuum emission we observe from these objects.

  • nkamraj[at]caltech[dot]edu
Dr. Margaret Lazzarini (she/her)

Postdoctoral Research Associate

I am a National Science Foundation Astronomy & Astrophysics Postdoctoral Fellow in the NuSTAR group at Caltech. I use multiwavelength observations of high mass X-ray binaries in nearby galaxies to constrain theoretical models of massive binary stellar evolution.

  • mlazz[at]caltech[dot]edu
Dr. Renee Ludlam (she/her)

NHFP Postdoctoral Fellow

My research focuses on modeling reprocessed X-ray emission (known as "reflection") in neutron star (NS) low-mass X-ray binary systems. The reflected emission has been broadened and blurred due to Doppler, General, and Special relativistic effects. The strength of these effects increases with proximity to the NS. Therefore by modeling these effects on the reprocessed emission, different properties of the system can be determined such as an estimate of the NS radius or magnetic field strength, as well as the density and ionization state of the accreting material.

  • rmludlam[at]caltech[dot]edu
Dr. Labani Mallick (she/her)

Postdoctoral Research Associate

My research focuses on black hole accretion in extreme gravity regimes as well as cosmic surveys. I perform spectral-timing analysis of accreting supermassive and intermediate-mass black holes using data from various space-based telescopes and study matter spiraling in the inner accretion flow. As a postdoctoral scholar at Caltech, I will work on the spectral analysis of a sample of accreting black holes, applying the most recent reflection models to NuSTAR and XMM-Newton observations.

  • lmallick[at]caltech[dot]edu
Dr. Guglielmo (Gullo) Mastroserio (he/him)

Postdoctoral Research Associate

I’m interested in accreting compact objects, especially to characterise the X-ray emission coming from the accretion disc. My research involves modelling characteristic features of accreting black holes using both spectral and timing techniques. I like coding and learning new and old program languages. I’m also involved in a few outreach projects particularly for young teenagers.

  • gullik[at]caltech[dot]edu
Dr. Yanjun Xu

Postdoctoral Research Associate

I'm interested in studying accreting black holes with X-ray observations. I analyze data from X-ray telescopes to unveil the behaviors and physical properties of these exotic compact objects created by nature.

  • yanjun[at]caltech[dot]edu

Our Graduate Students

Sean Pike (he/him)

Ph.D. Candidate

I study accreting compact objects and I am particularly interested in the timing and spectral properties of accreting neutron stars across a wide range of luminosities. I am also interested in the development of X-ray instrumentation with a focus on characterization of CdTe and CZT detectors.

  • spike[at]caltech[dot]edu
Yuhan Yao (she/her)

Graduate Student

I am interested in various types of high energy transients --- tidal disruption events, X-ray binaries, and stellar explosions. To explore these phenomena, I use the Zwicky Transient Facility (ZTF) and the SRG X-ray satellite as discovery engines, and conduct detailed follow up observations using other facilities including NuSTAR!

  • yyao[at]astro[dot]caltech[dot]edu