Dr. Javier A. Garcia

Research Assistant Professor of Physics

California Institute of Technology

Black Hole Physics X-ray Reflection Atomic Physics Spectral-Timing X-ray Polarization


I am an X-ray Astrophysicist at Caltech and member of the NuSTAR Science Team. I also hold a Senior Fellowship by the Alexander von Humboldt Foundation, which I carry at the Dr. Karl-Remeis Observatory in Bamberg, Germany. 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.

Bio Info:

I was born in Caracas, Venezuela, but raised in Maracaibo. There, I studied Physics in La Universidad del Zulia. I worked with Dr. Jurgen Stock at the CIDA on optical spectroscopy observing at Llano del Hato National Astronomical Observatory. I graduated from a 5-yr Physics program in 2003. I then moved to Caracas for my Master in Physics at the Venezuelan Institute of Scientific Research (IVIC). My thesis, on the calculation of atomic data for the X-ray spectrum of oxygen ions, was supervised by Profs. Claudio Mendoza and Manuel Baustista. I obtained my MS degree in 2005.

I moved to the US in the Fall of 2005 to start my PhD at The Catholic University of America, in Washington DC. The research was done at the NASA Goddard Space Flight Center with Dr. Timothy Kallman. My work included atomic data calculations for nitrogen ions, and developing models for the X-ray reflection of accretion disks around black holes. I obtained my PhD in Physics in the Fall of 2010.

Since then, I did postdocs with Prof. Christopher Reynolds at the University of Maryland; with Dr. Jeff McClintock at the Harvard-Smithsonian Center for Astrophysics; with Prof. Joern Wilms at the Dr. Karl Remeis-Sternwarte; and with Prof. Fiona Harrison at Caltech.

In 2021, I was awarded the Lab Astro Early Career Award from the AAS.

Research Interests

My research is focused on exploring the strong-field region around black holes, and other compact objects, by studying the detailed structure of the accretion disks and their observable signatures in the X-ray spectrum. Mass and spin---the two fundamental properties of black holes---deform and twist space-time in the inner regions, shaping the way material is accreted and dramatically affecting the emitted X-ray spectrum. Using radiative transfer, general relativity, and the most updated atomic data, I have developed and maintain sophisticated theoretical models for the interpretation of observational data from a large selection of past and present X-ray observatories. My ultimate goal is to deepen our understanding of the physical properties and temporal evolution of accreting black holes and neutron stars, in order to set observational constraints for fundamental physics in the strong gravity limit.

Selected Projects


Scientific Software & Resources

(More at my GitHub page)

Professional Profile

Employment History
  • Research Assistant Professor
    Caltech (since July 2019)
  • Postdoctoral Scholar
    Caltech (2016-2019)
  • Postdoctoral Fellow
    Harvard-Smithsonian CfA (2012-2016)
  • Postdoctoral Associate
    University of Maryland (2011-2012)
Education & Publications
  • PhD Physics (2010)
    Catholic University, Washington DC
  • Master Physics (2005)
    Venezuelan Institute for Scientific Research, Caracas, Venezuela.
  • Bachelor Physics (2003)
    Zulia University, Maracaibo,
Collaboration & Fellowships
  • NuSTAR Science Team
  • HEX-P Project Scientist
  • IXPE Science Team
  • Athena, StrobeX and Lynx Science Working Groups
  • Senior Fellow, Alexander von Humboldt Foundation at Dr-Karl Remeis Observatory

Video Presentations

Recorded public talks, school lectures, and conference presentations (some in Spanish)


I am enthusiastic about mentoring and transferring expertise and knowledge. I have supervised several students and postdocs in the US and abroad, and am always looking to expand my collaborations.

Current and Past Members

Joanna Piotrowska

Postdoc (2022-Present)

Oluwashina Adegoke

Postdoc (2022-Present)

Edward Nathan

Postdoc (2022-Present)

Labani Mallick

Postdoc (2021-Present)

Jameson Dong

Research Assistant (2022-Present)

Riley Connors

Postdoc (2017-2022)

Guglielmo Mastroserio

Postdoc (2019-2022)

Jerome Deprince

Postdoc (2020-2021)

Thesis Advising

* PhD Thesis Co-advisor, Kishalay Choundry, Fudan University, Shanghai, China

* PhD Thesis Advisor, Efrain Gatuzz, Venezuelan Institute of Scientific Research (IVIC), Caracas, Venezuela

* Undergrad Thesis Advisor, Raul Velasquez, La Universidad del Zulia, Maracaibo, Venezuela

Undergrad Summer Students at Caltech (SURF, WAVE, SRC)

* 2022: Mayra Velazquez, Qunfeng Jiang, Yash Gursahani, Sanyukta Agarwal

* 2021: Maryanne Xu, Eunice Beato, Jennifer Rodriguez, Hanbai Lyu, and Zhibo Yu

* 2020: Jessie Miller

* 2019: Feiyang Liu and Yerong Xu

* 2018: Honghui Liu

* 2017: Jingyi Wang, Zheng Cao, and Navin Sridhar


Dr. Javier A. Garcia
California Institute of Technology
Office 207, Cahill Center for Astronomy and Astrophysics
1200 E. California Blv, MC 290-17
Pasadena, CA, 91125

+1-(626) 395-6609
javier [at] caltech.edu