Home | Caltech HEA Group Caltech High Energy Astrophysics Group High Energy Astrophysics Group Home of the Caltech NuSTAR and UVEX Science Teams Research Interests NuSTAR NuSTAR is the first focusing hard X-ray satellite in orbit, providing more than two orders of magnitude improvement in sensitivity as compared to previous high-energy missions working at similar energies. The primary science goals of NuSTAR are broad, and include studying a range of high-energy sources, including black holes, supernovae explosions, neutron stars, relativistic jets, and the Sun. Visit Website UVEX UVEX is a new NASA Medium Explorer mission to explore the ultraviolet sky, with an expected launch date in 2030. With a wide-field, two-band ultraviolet imager and long, multi-width slit spectrometer, UVEX will address outstanding questions in our understanding of the Universe, including the nature of the low-mass, low-metallicity galaxy population and the early ultraviolet emission of explosive transients. UVEX will also leave a rich legacy of all-sky ultraviolet data. Visit Website Accreting Compact Objects Accreting compact objects, such as black holes and neutron stars bend and twist space-time, or contain degenerate matter with unique properties. We use X-ray telescopes like NuSTAR (among others) to observe the high-energy emission from these objects in binary systems, in which the compact object is gravitationally tied to a stellar companion. Learn More ULXs Ultraluminous X-ray Sources (ULXs) are X-ray binaries in other galaxies undergoing such extreme accretion that they are some of the most luminous X-ray sources in the nearby Universe outside of the centers of galaxies. Learn More More Research! There's a whole lot more for NuSTAR to look at beyond accreting compact objects and ULXs alone! Click below to hear about some more of the fascinating topics that our team devote their time to exploring. Learn More Group Members Meet the High Energy Astrophysics Group! Upcoming and Recent Group Activity Jul 5 Gaurav attends the SPIE Astronomical Telescopes + Instrumentation meeting SPIE is the international society for optics and photonics and held the SPIE Astronomical Telescopes + Instrumentation meeting in Copenhagen, Denmark. Postdoc Gaurav Waratkar attended the meeting and presented a talk entitled Beyond NuSTAR: characterization of thicker, broadband Redlen CZT detectors for next-generation x-ray telescopes where he reported on his results from his in-house laboratory tests of new X-ray detectors. The team characterized the new Redlen CZT detectors and demonstrated that, despite no cooling, these detectors show better spectral performance than NuSTAR flight detectors -- thus supporting their use in future hard X-ray instruments. Jun 22 Hannah attends the Breaking the Limits meeting Staff Scientist Hannah Earnshaw traveled to Sardinia, Italy to attend the Breaking the Limits 2026 meeting. The conference was on the topic of super-Eddington accretion on compact objects, which can apply to a variety of systems, such as supermassive black holes, black hole binaries, ULXs, neutron stars. Hannah talked about their results on The evolving broadband spectrum of NGC 4190 ULX-1. NGC 4190 ULX-1 is among our closest and most accessible ULXs to study. Hannah presented the results of a recent sequence of XMM-Newton and NuSTAR observations, over which the source shows dramatic changes in its accretion disk component and its high-energy (>10 keV) tail, and placed them in the context of Swift monitoring and archival datasets in order to determine the changing geometry of the system. Jun 16 The HEA Group welcomes this year's summer students! The arrival of summer brings the lastest group of SURF, WAVE and other undergraduate researchers to Caltech, here for 10 weeks to undertake summer research. The HEA Group welcomes Tooba Ansar, Michael Burch, Wenda Chen, Mercan Demiroglu, Kenji Farrell, Ferdinand, Zoe Granadoz, Adam Janik, Sam Nasri, Maya Nunez, Sarah Pinto, Amelie Rajab and Benjamin (Yuchi) Zhang. Read all their bios here. Wishing you all a productive and fun time with us! Jun 14 The HEA group attends AAS 248 The 248th meeting of the American Astronomical Society was held is Pasadena and several members of the HEA group took advantage of its proximity to attend. Postdoc Shina Adegoke spoke about his results on A Comprehensive View of the 2021 Outburst of GX 339-4 and Its Implications for Accretion and Reflection, staff scientist Hannah Earnshaw presented NuSTAR Overview and Status at 14 Years, postdoc Elias Kammoun spoke about his results on X-raying the inner accretion flow of two double-peaked emitters, postdoc Demet Kirmizibayrak spoke about her results on Compact objects through novel timing methodologies, graduate student Evangela Shread spoke about her results on Predictions for Local Volume Dwarf Galaxy Discovery in the LSST Era, postdoc Gaurav Waratkar spoke about his results on NuSTAR as an All-Sky GRB Monitor: The SINGS Automated Pipeline and postdoc Xiurui Zhao spoke about his results on A Significantly Variable AGN Corona in Mrk 509 and Transient Relativistic Iron Emission Line from an X-ray Flaring Supermassive Black Hole. Xiurui also gave a press conference on his results which can be seen on YouTube and his work was featured in several news websites news websites. Jun 13 NuSTAR turns 14! Fourteen years ago NuSTAR was launched from a Pegasus rocket into low-Earth orbit and began its mission of observing the high-energy X-ray sky. The NuSTAR team celebrated this milestone by running a Special Session at the 248th meeting of the American Astronomical Society, held in Pasadena, celebrating 14 years of NuSTAR science and looking at what the future holds for high-energy X-ray astronomy. Congratulations NuSTAR! Jun 8 Murray attends the X-ray Universe meeting Staff Scientist Murray Brightman traveled to Elche, Spain to attend the X-ray Universe 2026 meeting. The conference series is aimed at encompassing a broad range of high-energy astrophysics topics, from solar system studies to cosmology and at providing a showcase for results and discoveries from XMM-Newton as well as from the variety of other current missions. Murray was invited to talk about his results on transient ultraluminous X-ray sources and also presented his recent results on Fast X-ray transients in NuSTAR data. Jun 2 Xiurui is awarded Keck and Palomar time! Postdoc Xiurui Zhao was awarded observing time at Keck Observatory and Palomar Observatory for the 2026B semester. He was awarded a quarter night on Keck using the OSIRIS-LGS instrument to study the metallicity dependence of microlensing planet-hosting M Dwarfs and a night on Palomar using the NGPS instrument to complete a census of Swift-BAT Hard X-ray Survey Detected AGN. Congratulations Xiurui! May 28 Gia and Elias get XRISM time in Cycle 3! The results from X-ray Imaging and Spectroscopy Mission (XRISM) Cycle 3 review have been published and graduate student Gia Karavangelas and postdoc Elias Kammoun have been awarded observations. Gia will study the ultrafast winds being driven by the quasar 4C+74.26 and Elias will look for signatures of two supermassive black holes orbiting each other at the center of the galaxy IC 4709. Congratulations to them both! Apr 16 Several group members get NuSTAR time in Cycle 12! The results of the NuSTAR Cycle 12 review have been released. Among the successful proposers were group members Murray, Brian, Elias and Dan and Xiurui. The group members will use NuSTAR to study transient ultraluminous X-ray sources, accreting supermassive black holes, a neutron star in our Galaxy and more! Congratulations all! Apr 16 Asia is featured in the Caltech Weekly newsletter! Did You Know? Modern astronomy is drowning in data, making machine learning a crucial method of sifting through it all, as postdoc Asia Piotrowska explains in this short Instagram video. It was in response to the question "How do astronomers use AI for discoveries?" asked to #AskCaltech and was featured in the Caltech Weekly newsletter. Apr 4 Asia and Gaurav take part in the Night of Ideas Postdocs Joanna (Asia) Piotrowska and Gaurav Waratkar participated in the Night of Ideas in Los Angeles, contributing to a series of public-facing science activities. As part of the program, the team led “Solar S’mores,” an interactive demonstration introducing solar observations and the basic principles of telescopes. Using focused sunlight to safely heat marshmallows, participants—especially younger attendees—were able to explore how telescopes collect and concentrate light, turning a classic campfire treat into a hands-on physics experiment. In addition, Asia delivered an outreach talk on the nature of black holes, covering the fundamentals of general relativity and the key observational evidence for their existence. The talk highlighted how astronomers use X-ray observations and other techniques to probe the extreme environments around black holes and test our understanding of gravity. The event provided an opportunity to engage a broad audience with modern astrophysics through both interactive demonstrations and accessible scientific discussion. Mar 20 Yuanze's paper is accepted for publication by the Astrophysical Journal Graduate student Yuanze Ding's paper UGC 2369S: a Kpc Scale Triple Merger Candidate Identified in a Nearby Luminous Infrared Galaxy has been accepted for publication by the Astrophysical Journal. In it Yuanze and collaborators studied a nearby galaxy that is very luminous in the infrared using high resolution imaging at X-ray, radio and optical and near-infrared wavelengths finding evidence for three supermassive black holes accreting from their surroundings separated by just 3 kiloparsecs. Congratulations Yuanze! Feb 23 Xiurui gets time on Palomar to use its new spectrograph Postdoc Xiurui Zhao got awarded three nights on The Hale Telescope at Palomar in the recent call for proposals. He will use the new Next Generation Palomar Spectrograph (NGPS) to confirm the nature of hard X-ray sources, measuring their redshifts and black hole masses. The observations will complete the optical spectroscopic survey of the newly discovered hard X-ray sources in the 150 month BAT catalog. Congratulations Xirui! Feb 9 Xiurui's paper is accepted for publication! Postdoc Xiurui Zhao's paper Transient Relativistic Iron Emission Line from an X-ray Flaring Supermassive Black Hole has been accepted for publication by the Astrophysical Journal. In it Xiurui and collaborators report the discovery of the first transient relativistic emission line from iron seen from an accreting supermassive black hole, 22 days after an X-ray flare was seen from the source. It provides evidence of the response of the accretion disk to X-ray flares and offers a new method to probe black holes and accretion physics. Congratulations Xirui! Feb 9 Evangela submits her paper to the Astrophysical Journal Graduate student Evangela Shread has submitted her paper on Dwarf Galaxy Number Counts within 25 Mpc: Predictions from Local Group Analogues in TNG50 to the Astrophysical Journal. In it Evangela and collaborators used simulations to predict the number of low-mass dwarf galaxies that will be detected by observatories such as LSST, Euclid and Roman finding that up to 12,000 of them could be detected within 25 Mpc. Good luck Evangela! Feb 4 Ipek's first first-author paper is published! Graduate student Ipek Kerkeser's paper on Investigating H II Regions in the Disk of NGC 7331 with the Circumgalactic Hα Spectrograph has now been published. In it Ipek and collaborators investigated the motions of ionized hydrogen in the nearby galaxy NGC 7331 which trace recent star formation and provide insight into the interactions between stellar feedback and the interstellar medium (ISM). This was Ipek's first first-author paper, congratulations! Jan 30 Brian briefs NASA about NuSTAR observations of 3I/ATLAS Last week, Research S…