Camille Diez
About me
Hi, I am Camille and I am currently a Research Fellow at the European Space Agency (ESA) based at the European Space Astronomy Centre (ESAC) near Madrid, Spain.
I was previously a doctoral candidate at the Institut für Astronomie und Astrophysik (IAAT) in Tübingen, Germany, where I obtained my PhD degree in astrophysics in May 2023.
Before that, I was a trainee at the Institut de Recherche en Astrophysique et Planétologie (IRAP) in Toulouse, France. I completed my master degree in astrophysics (2019) at the Université Toulouse III - Paul Sabatier also in Toulouse, France.
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My research interests focus on the broadband X-ray study of accreting neutron stars in binary systems and their local environment. I am also deeply engaged in promoting women in science and making astrophysics accessible through my outreach efforts.
Research interests
For a full description
Stellar winds in HMXBs
I study accretion phenomena around compact objects. In particular, I analyse stellar winds in high-mass X-ray binaries, systems consisting of a compact object with a giant companion star.
X-ray astronomy
I am an observer and have strong expertise with the current X-ray fleet. Recently, I have been involved with the XRISM mission during the performance verification phase.
I also contributed to a public guide for complex XMM-Newton data extraction.
Neutron star properties
I am interested in understanding dense matter properties and magnetic field configuration onto neutron stars thanks to their extreme densities and via the analysis of spectral signatures caused by their intense magnetic fields.
Main publications
The XMM-Newton mission has been a cornerstone of ESA’s X-ray astronomy efforts, with its Science Analysis System (SAS) providing essential tools for data processing. To modernise and streamline this workflow, the new XMM-SAS Datalab integrates SAS into ESA’s cloud-based Datalabs platform via a user-friendly, Python-based JupyterLab interface. Our case study using Vela X-1 analysis from Diez et al. (2023) confirms the platform’s reliability, marking a key step toward more efficient and accessible X-ray data analysis in the era of cloud-based astronomy.
jaxspec is a new Python package designed to modernise X-ray spectral analysis by offering fast, reliable, and fully Bayesian inference using the JAX ecosystem. We demonstrate its accuracy and speed on complex models and high-resolution data, including a reproduction of Hitomi’s results on the Perseus cluster. With support for advanced methods like variational inference, jaxspec bridges X-ray spectroscopy with modern machine learning, paving the way for future missions like Athena's X-IFU.
High-mass X-ray binaries like Vela X-1 offer a unique opportunity to investigate accretion onto compact objects and the wind structure in massive stars. By combining XMM-Newton and NuSTAR data at orbital phases 0.36–0.52, we tracked, with 283 s resolution, the onset of the dense accretion wake crosses our line of sight and identified fluctuations likely due to clumps. During high-absorption intervals we also detected multiple fluorescent emission lines from highly ionizsd species (0.5–4 keV), revealing detailed photoionisation of the stellar wind.
We analysed two new NuSTAR observations of the high-mass X-ray binary Vela X-1 at orbital phases ~0.68–0.78 and ~0.36–0.52 which reveal rapid spectral changes down to the pulse period timescale. We confirm that the photon index and, at low fluxes, the folding energy anti-correlate with luminosity, implying a change of properties in the Comptonising plasma. Strong absorption variability, both between and within observations, points to large-scale wind structures, such as accretion and photoionisation wakes, modulated by our changing line of sight.
Outreach
Even though I have a strong affinity for fundamental research, I'm also equally passionate about taking part in outreach activities such as advocating for the recognition of women in science and sharing the marvels of science with a non-scientific audience or with students, both through public talks and teaching. Whether it's presenting at scientific conferences as part of my job or just indulging my enthusiasm, I love learning, communicating and sharing knowledge, in English or French.
Teaching & school activities
I deeply value teaching because it is such an efficient way to share expertise and inspire students to explore the scientific community. During my PhD, I led 90 hours of Astronomy and Astrophysics exercise classes and, in 2024, earned the French Maître de Conférences qualification. I've also presented what it’s like to be an astrophysicist and what our day-to-day work consists of at a secondary‑school careers fair two times.
Public speaker
I am regularly invited as a speaker for round tables for astro/scientific events such as Chercheuses d'étoiles organised by UPS in Space or for the Rencontres Tranfrontalières d'Astronomes Amateurs organised by SAPCB to share my experience as a young researcher.
Scientific outreach
I really enjoy giving public talks as they are a great way to make astrophysics easy to understand for non-scientists. I was recently interviewed for a science documentary about black holes by the French YouTuber Zebroloss, who is the official representative for French-speaking countries in ESA’s influencer program.
Women in astrophysics
Recognising women in science is very important to me. I do my part to raise awareness, inspired by amazing women like Jocelyn Bell on the picture above. As a member of the Equity, Diversity, and Inclusion (EDI) office at ESA, I help create changes to overcome the gender barriers that still exist in science.
Contact me
Camille Diez
European Space Astronomy Centre (ESAC)
Camino Bajo del Castillo s/n,
Villanueva de la Cañada, 28692 Madrid, Spain
