Research Interests


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.

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.


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.

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.

Group Members

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Upcoming and Recent Group Activity

  • May 23

    Murray, Brian and Hiro are recognised by Caltech for their years of service to the institute

    Staff Scientists Murray Brightman, Brian Grefenstette and Hiro Miyasaka were recognised by Caltech at The 69th Annual Staff Service & Impact Awards, Murray for 10 years of service, Brian for 15, and Hiro for 20! They received a certificate and had their pictures taken with the President of Caltech, Dr. Thomas Rosenbaum at an event at Beckman Auditorium.

  • May 6

    The HEA group celebrates Black Hole Week 2024

    The first week of May is Black Hole Week and Shina, Asia and Dan took to social media to answer questions from the public about about these strange balls of gravity. Asia and Dan featured in a ScienceAtNASA YouTube video explaining what black holes are, and Dan and Shina answered questions from the public on the NASA Universe X account.

  • Apr 24

    Hannah's paper is accepted for publication!

    Staff Scientist Hannah Earnshaw's paper entitled Return to the forgotten ULX: a broadband NICER+NuSTAR study of NGC 4190 ULX-1 has been accepted for publication by the Astrophysical Journal. NGC 4190 ULX-1 is a bright ultraluminous X-ray source in the nearby galaxy NGC 4190 and is nicknamed the forgotten ULX since while it is relatively bright and nearby, it hasn't been studied in detail until now. Hannah found that despite the lack of detected pulsations, there is tantalizing evidence for NGC 4190 ULX-1 being a candidate neutron star accretor from its variability properties. Hannah has also been awarded joint NuSTAR and XMM-Newton observing time to study this source further in NuSTAR Cycle 10. Congratulations Hannah!

  • Apr 22

    NuSTAR Cycle 10 results are out!

    The results of the NuSTAR Cycle 10 review have been released. Among the successful proposers were group members Shina, Peter and Hannah, as well as former members Matteo, Felix, Amruta, Javier, Gullo, Sean and Yuhan. Find out all about the proposed science in Cycle 10 here. Congratulations all!

  • Apr 7

    The HEA Group travels to Texas for HEAD 21 and the solar eclipse

    Several members of the group inlcuding Shina, Murray, Brian, Asia, Ed and Dan travelled to Horseshoe Bay, Texas to attend the 21st Meeting of the High Energy Astrophysics Division of the AAS. There they presented their recent findings and met with other members of the high energy astrophysics community. Javier also received his HEAD innovation prize along with his colleagues Dr. Thomas Dauser and Dr. Tim Kallman. The venue was in the path of totality for the 2024 North American solar eclipse. Despite some cloud cover, the group got to see the solar corona in all its glory.

  • Mar 25

    Ed does astronomy on tap

    Postdoc Ed Nathan gave a talk at Astronomy on Tap. He gave a talk entitled “Black Holes: Dining with the Stars” in which he described the various masses that black holes have, including primordial black holes. He even posited if there is a black hole at the center of our Sun (there probably isn't).

  • Feb 13

    UVEX is selected!

    UVEX: The Ultraviolet Explorer has been selected for flight and is targeted to launch in 2030 as NASA’s next Astrophysics Medium-Class Explorer mission. Congratulations to the Principal Investigator Professor Fiona Harrison and the entire UVEX team! For more details about UVEX's selection, you can read the press release. Additionally, check out this video to learn more about UVEX and the remarkable journey ahead.

  • Feb 7

    Peter gives a virtual talk at New York University Abu Dhabi

    Postdoc Peter Boorman gave a virtual talk as part of the "Variable Sources in Galaxies" workshop at New York University Abu Dhabi. The workshop was dedicated to astrophysical systems that display variability in galaxies, and Peter presented the latest compilation of Compton-thick AGN identified to-date with NuSTAR as well as prospects for the future with HEX-P. NuSTAR's unique passband is crucial for revealing complex changes in the X-ray spectrum of such sources and revealing variability at high X-ray energies.

  • Feb 6

    Asia gives a colloquium at Pomona College

    Postdoc Asia Piotrowska gave the Physics and Astronomy Colloqium at Pomona College. The title of the talk was "Putting the breaks on star formation in galaxies: the cosmological impact of supermassive black holes". Her talk was well received and she got many questions from the audience.

  • Jan 11

    The HEA Group attends AAS 243

    Several members of the HEA Group traveled to New Orleans to attend the 243rd Meeting of the American Astronomical Society (AAS 243). Asia talked about the integrated effect of black hole feedback on galaxies, Brian presented his work on early hard X-rays from the nearby core-collapse supernova SN2023ixf, Murray presented his results on a new sample of transient ultraluminous X-ray sources and Peter talked about probing the circum-nuclear environment of growing supermassive black holes with HEX-P.

  • Jan 10

    Javier wins the HEAD innovation prize!

    Former HEAG member, Dr. Javier Garcia, won the HEAD innovation prize along with his colleagues Dr. Thomas Dauser and Dr. Tim Kallman for the development of novel models to describe emission in the strong gravity regime from accreting compact objects. The relxill models they compiled are used extensively in the X-ray astrophysics community. Congratulations Javier!

  • Dec 24

    NuSTAR observes 4U 1630-472 for Shina

    4U 1630-472 is a transient black hole candidate that has been known to go into regular outbursts since its discovery in 1969. Recently it has been showing signs of increased activity again and postdoc Shina Adegoke requested a directors discretionary time observation with NuSTAR in order to investigate the source. He reported on his results in an ATel this week. Well done Shina!

  • Dec 20

    Brian is appointed to the PhysPAG Executive Committee

    Staff Scientist Brian Grefenstette has been appointed to the Physics of the Cosmos Program Analysis Group (PhysPAG) Executive Committee. The PhysPAG serves as a community-based, interdisciplinary forum for soliciting and coordinating community analysis and input in support of Physics of the Cosmos objectives and of their implications for architecture planning and activity prioritization and for future exploration. The Executive Committee's responsibilities include organizing meetings and collecting and summarizing community input with subsequent reporting to the Astrophysics Division Director. Congratulations Brian!

  • Dec 15

    Come and do summer research in the HEA group next summer!

    The HEA group is offering up to 8 SURF opportunities for the summer of 2024. The SURF projects on offer will be in all group research areas and be mentored by the staff scientists and postdocs of the group. Caltech students will be prioritized, however we welcome applications from other universities and will consider them once Caltech students have been taken care of. Interested students should email heag[at]caltech[dot]edu listing which areas of HEAG research they are most interested in and/or which mentors they are most interested in working with, preferably listed by preference, and a CV. We expect to carry out interviews with prospective candidates by the end of January/beginning of February in preparation for the SURF application deadline on February 22, 2024. The HEAG also welcomes WAVE students which has a separate application procedure. These are due January 9, 2024.

  • Dec 11

    Murray gets XMM-Newton time

    The results of XMM-Newton's Cycle 23 proposals have been released. Among the successful proposals were two of Staff Scientist Murray Brightman's, both target of opportunity observations to study ultraluminous X-ray sources. One to study the 8.56 keV absorption line in NGC 4045 ULX in more detail, the other to observe a newly discovered transient ULX. Congratulations Murray!

  • Nov 20

    Ed gets NICER time

    The list of successful NICER Cycle 6 proposals was posted this week. Postdoc Ed Nathan's proposal to study the black hole X-ray binary GRS 1915+105 was among them. He aims to use NICER and NuSTAR to study the source's quasi-periodic oscillation in order to study the corona. Congratulations Ed!

  • Nov 15

    NuSTAR observes GRB 231115A

    NASA’s Fermi’s Gamma-ray Burst Monitor announced the detection of a Gamma-ray Burst named GRB 231115A. The event was of specific interest due to its position, given by ESA’s INTEGRAL observatory, being coincident with the nearby galaxy M82 (aka the “Cigar Galaxy”). NuSTAR initiated a Target of Opportunity observation requested by NuSTAR scientist Brian Grefenstette in order to study the prompt afterglow and was on target only 4 hours after the request was approved, and only 7 hours after the event itself, both records for NuSTAR. Brian posted the results of the observation via a GCN circular.

  • Nov 9

    HEX-P papers make a splash on arXiv!

    More than 15 science white papers have been written in support of the High Energy X-ray Probe (HEX-P) concept lead by NuSTAR project scientist Daniel Stern. They all appeared on the arXiv this week, detailing all the great science HEX-P will do. Several HEA group members were involved including Asia, Amruta, Dan, Murray and Peter. Find out more about HEX-P here and read the papers here

  • Oct 16

    Murray takes part as an expert in NASA's Astrophoto Challenge

    NASA's Astrophoto Challenge is a periodic opportunity for learners of all ages to create their own multi-color/multi-wavelength images of famous celestial objects using both ground-based telescopes and data from space-based NASA/ESA telescopes. The 2023 Summer NASA's Astrophoto Challenge focussed on the Phantom Galaxy, M74. For these challenges, participants were able to take their own data with the MicroObservatory robotic telescope network, or use a curated set of data from the following NASA and ESA missions: Webb, Hubble, Chandra, Spitzer, and XMM-Newton. Staff Scientist Murray Brightman lent his expertise in X-ray astronomy, and appeared in a short video explaining where X-ray emission in M74 comes from. See some of the standout entries here!

  • Oct 9

    Lea Marcotulli visits the HEA Group

    Lea is a NASA Einstein Fellow at Yale and is an expert on X-ray and gamma ray emission from AGN and blazars. She will give a talk entitled "The most powerful persistent jets through cosmic time" on Monday, October 9th at 16:00 in Cahill room 370.

  • Sep 11

    Peter's book chapter is published!

    Long-term NuSTAR group collaborator Johannes Buchner and NuSTAR postdoc Peter Boorman published a textbook chapter in the Handbook of X-ray and Gamma-ray Astronomy. The chapter gives a review of the statistical methods involved with X-ray spectral fitting, including a number of hands-on exercises and example code and they posted it on arXiv. Nice work Peter and Johannes!

  • Sep 11

    Asia does astronomy on tap

    Postdoc Asia Piotrowska will give a talk about how supermassive black holes shape their host galaxies at Astronomy on Tap on Monday, September 11 at 7:30PM at the Dog Haus Biergarten. The event also features live music by Jason Achilles and Forrest Mitchell.

  • Sep 11

    Núria Torres-Albà visits the HEA Group

    Núria is a postdoctoral fellow at Clemson University and is an expert in high-energy studies of active galaxies. Núria will be visiting for the entire week (September 11—15) and will be in Cahill room 268. She will give a talk entitled "X-raying the Torus: A multi-epoch study of obscuration in nearby AGN" on Monday, September 11th at 16:00 in Cahill room 370.

  • Aug 24

    The summer students present their work!

    Diana Avila, Joahan Castaneda Jaimes, M Gardner, Annie Giman, Sanya Gupta, Dylan Perez, Vismaya Pillai and Miranda Zak, who spent the summer doing research in the HEA Group, presented their work in oral and poster formats, concluding their time with us. We wish them all the best in their future endeavours! Do you want to join us for summer research? WAVE applications are due in January 2024 and SURF applications are due in February.

  • Aug 21

    Johannes Buchner visits the HEA Group

    Johannes is a post-doctoral researcher at MPE in Germany working on a wide array of astrophysical phenomena including black holes, gamma ray bursts, and exoplanets. He is also an expert in astrostatistics, notably being the creator of the UltraNest nested sampling package and numerous other widely-used astrophysical packages. He visited the group and gave a talk entitled "Can we measure the host galaxy mass of Seyfert 1?".

  • Aug 14

    Asia attends a machine learning workshop

    Postdoc Asia Piotrowska traveled to Heidelberg, Germany to attend a workshop on machine learning in astrophysics. The meeting focused on bringing senior experts, early career researchers and students in natural sciences and mathematics to work on a range of astrophysical problems. The workshop combined lectures, tutorials and individual short projects, materials for all of which are publicly available here.

  • Aug 14

    Margaret starts a new job at Cal State LA

    Postdoc Margaret Lazzarini starts her new job as Assistant Professor in the Physics and Astronomy Department at Cal State LA after spending two years in the HEA Group. Congratulations Margaret!

  • Aug 5

    Margaret's summer students give their final presentations

    Michael Aguiniga, David Chau, Jessie Serrano, & Rayana Yasin, high-school students who were working with postdoc Margaret Lazzarini for the summer as part of Caltech's Hybrid Summer Research Connections (HSRC) program, gave their final presentations on Saturday, August 5. Congratulations!

  • Aug 1

    Shina attends a high resolution X-ray spectroscopy workshop

    Postdoc Shina Adegoke traveled to MIT to attend a workshop on high-resolution X-ray spectroscopy. There he presented his work on X-ray reflection spectroscopy of the transient black hole candidate MAXI J1803-298.

  • Jul 24

    Chandra Cycle 25 results are out!

    The list of approved targets for Chandra's Cycle 25 have been posted. Both Daniel and Murray were awarded target of opportunity observations to observe X-ray transient sources. Congratulations both!

  • Jul 24

    Ryan Pfeifle visits the HEA Group

    Dr. Ryan Pfeifle visited the HEA Group for a week and gave a talk on his research on hunting for dual AGNs in the hard X-rays. Ryan is an expert on multi-wavelength studies of merging galaxies & dual AGN with a focus on X-ray imaging and spectral analyses.

  • Jul 12

    Asia presents at EAS 2023

    Postdoc Asia Piotrowska travelled to Krakow, Poland to attend the European Astronomical Society Annual Meeting. There she gave a talk on constraining black hole growth history with population spin measurements using HEX-P and presented her results on supermassive black hole feedback in galaxies.

  • Jul 1

    Dan attends the lauch of Euclid

    NuSTAR Project Scientist Dan Stern attended the launch of Euclid, a space telescope designed to explore the evolution of the dark Universe. Dan is also the Deputy PI of the NASA-Funded Euclid Science Team.

  • Jun 27

    Brian gives a presentation about NuSTAR to the NASA Astrophysics Advisory Committee

    Staff Scientist Brian Grefenstette gave a presentation at the APAC meeting which had a focus on Time Domain and Multi-Messenger astrophysics. He talked about NuSTAR's continuing contribution to the field through its follow up of transient X-ray phenomena.

  • Jun 21

    The HEA Group welcomes the SURF/WAVE fellows of 2023

    The arrival of summer brings the lastest group of SURF and WAVE fellows to Caltech, here for 10 weeks to undertake summer research. The HEA Group welcomes Diana Avila, Joahan Castaneda Jaimes, Madeline Gardner, Annie Giman, Sanya Gupta, Dylan Perez and Miranda Zak. Wishing you all a productive and fun time with us!

  • Jun 19

    Ed travels to Europe for conferences in Greece and Italy

    Postdoc Ed Nathan attended The X-ray Universe conference in Athens, Greece and the Vasto Accretion meeting in Vasto, Italy. He presented a poster to both conferences entitled "Polarised reflection: Creating polarised XILLVER tables" and in Vasto he presented a talk entitled "Phase-resolved spectroscopy of QPOs seen in simultaneous NuSTAR & XMM-Newton observations of H1743-322 across multiple outbursts". The meeting was also covered by the local press which featured Ed in its photos!

  • Jun 8

    Asia takes part in a summer physics camp for young women

    Postdoc Asia (Joanna) Piotrowska connected online with this year’s participants of the Summer Physics Camp for Young Women held jointly in Santa Fe, NM and Hilo, HI. During the ‘Space Chatter’ event, camp students had an engaging conversation with Asia about supermassive black holes and cosmology, learning how NuSTAR observations allow us to measure the properties of some of the most exotic objects in the Universe. In tandem with discussing science, students also had an opportunity to ask Asia about her experience of pursuing a professional career in science as a woman and as for advice on subject choices in the future.

  • Jun 8

    Brian submits his paper on SN 2023ixf

    Staff Scientist Brian Grefenstette submitted his paper on early hard X-rays from the nearby core-collapse supernova SN2023ixf. He used NuSTAR to measure the brightness and absorption in the X-rays, and infer the mass-loss rate of the progenitor star.

  • Jun 4

    Yuanze goes to AAS 242

    Graduate student Yuanze Ding traveled to Albuquerque, New Mexico for the 242nd Meeting of the American Astronomical Society (AAS242). There he presented his results on high density corrections to the XILLVER reflection model commonly used to fit the X-ray spectra of AGN and X-ray binaries.

  • May 31

    Lynnie defends her thesis!

    Graduate student Lynnie Saade successfully defended her PhD thesis entitled “Unveiling Supermassive Black Hole Growth and Co-evolution Using X-rays”. In July, she will start a postdoctoral researcher position at NASA's Marshall Space Flight Center working on IXPE. Congratulations Lynnie!

  • May 29

    Margaret's paper on high mass X-ray binaries in M33 is accepted for publication

    Postdoctoral fellow Margaret Lazzarini's paper on the high mass X-ray binary population of nearby galaxy M33 was accepted for publication in the Astrophysical Journal. Congratulations Margaret!

  • May 22

    Yuhan defends her thesis!

    Graduate student Yuhan Yao successfully defended her PhD thesis entitled “High Energy Transients Powered by Black Holes”. In August, she will start a Miller fellowship at UC Berkeley. Congratulations Yuhan!

  • May 19

    NuSTAR detects hard X-rays from a nearby supernova

    The closest supernova in a decade, SN 2023ixf, was found in the Pinwheel galaxy (M101) and is thought to have been produced by the collapse of a massive star. Telescopes all over the world, and in space, rushed to observe this rare event. Staff Scientist Brian Grefenstette organised for NuSTAR to observe it, and reported on the detection of hard X-rays in an Astronomer's Telegram

  • May 12

    Peter gives a talk to an Astronomy Club

    Peter Boorman gave a lecture to the Antelope Valley Astronomy Club in Palmdale. The talk overviewed the history of X-ray astronomy, and the different multi-wavelength techniques available today to identify and study accreting supermassive black holes observationally. The talk also presented some of the exciting research highlights from the past ~11 years of NuSTAR operation and the prospects on the horizon with the High Energy X-ray Probe mission concept.

  • May 4

    Murray's paper on transient ULXs is accepted for publication

    Staff Scientist Murray Brightman's paper on a new sample of transient ultraluminous X-ray sources he found was accepted for publication by the Astrophysical Journal. Congratulations Murray!

  • May 1

    Dr. Asia (Joanna) Piotrowska joins the HEA Group

    Asia joins us from Cambridge University in the UK as a postdoctoral researcher. Welcome Asia!

  • Apr 29

    HEA Group members volunteer at Explore JPL

    NASA's Jet Propulsion Laboratory held their annual open house event, Explore JPL, which is a chance for visitors to to learn more about space exploration, robotics, and technology being developed. HEA Group members Ed, Lynnie, Peter and Shina took part to share their knowledge on NuSTAR and black holes.

  • Apr 24

    Karl attends IACHEC

    NuSTAR Science Operations Manager, Karl Forster, attended the 15th meeting of the International Astronomical Consortium for High-Energy Calibration (IACHEC) in Pelham, Germany. These annual meetings bring together calibration teams from all the high-energy astrophysics missions in operation, development and those being planned. The years of experience of the IACHEC members has helped with the calibration of many missions, including NuSTAR, and these annual working meetings provide a forum for the community to discuss and coordinate calibration activities.