Camille Diez
About me
Hi, I am Camille and I am an astrophysicist with strong expertise in X-ray observations. I am currently a Research Fellow for the CNES (French Space Agency) based at the Institut de Recherche en Astrophysique et Planétologie (IRAP) in Toulouse, France.
I was previously a Research Fellow for the European Space Agency (ESA) based at the European Space Astronomy Centre (ESAC) near Madrid, Spain. I obtained my PhD degree in astrophysics in May 2023 at the Institut für Astronomie und Astrophysik (IAAT) in Tübingen, Germany.
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 with strong expertise in
X-rays. I have been involved with the XRISM mission during the PV 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 via the analysis of spectral signatures caused by their intense magnetic fields.
Main publications
4U 1538--52 in a Heartbeat
High-mass X-ray binaries like 4U 1538-52 are important systems for studying accretion mechanisms onto compact objects. We report on the first out-of-eclipse observation of this source with simultaneous XMM-Newton and NuSTAR coverage. We observed a bright flare followed by a luminosity dip forming a heartbeat-like episode, and by local absorption peaks that can be attributed to clumps/filamentary structures embedded in the accretion wake behind the neutron star. These results are further supported and reproduced by 3D hydrodynamic simulations
We report, for the first time, on a XRISM observation of the HMXB Vela X-1 complemented by simultaneous XMM-Newton and NuSTAR coverage. We investigated the Fe region, and we report for the first time the presence of a Fe Kα doublet in the spectrum of Vela X-1 produced in cold clumps embedded in the hot ionised wind. The measured line velocities of the order of 100 km/s are consistent with production sites in the vicinity of the neutron star. This precursor study with Vela X-1 shows the potential of XRISM to study in unprecedented detail the spectral evolution of wind-accreting X-ray binaries.
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 NewAthena'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.
Contact me
Camille Diez
CNES - IRAP,
9 avenue du Colonel Roche,
Toulouse, 31028 Cedex 4, France
