Raphaël Bendahan-West

About Me

I am a PhD student working with Sebastian Marino and Sasha Hinkley in the Departement of Physics & Astronomy at the University of Exeter. My PhD consists in explaining and understanding the different morphology seen in debris discs by testing the different planet-disc interaction theories, and evaluating the role of planets in the truncation of discs. These discoveries will ultimately also test different debris disc and planet formation theories.

For my Masters, I worked on detecting transits of exocomet bodies with spectroscopy. I performed a systematic search for these exocomet transits using all HARPS data, and was able to define an exocomet occurence rate for such transits observed through transient absorption features in the ionised calcium doublet. If interested in the field of exocomets, I recommend reading Strøm et al. 2020. Look out for a series of more in-depth and up to date review papers on Exocomets, which are the work following an interdisciplinary workshop at ISSI Bern!

Research Interests:
Debris disc morphology
Exoplanet detection with direct imaging
Planet-disc interactions
Planet/debris disc formation
Exocomet transit detection

Other Interests:
Other than my interest in Astronomy, I have been playing basketball competitively for a large percentage of my life in national/county/university leagues. While doing my PhD in Exeter, I joined the Exeter University Basketball Club (Men's 1st Team captain 2024-2025). From 2017 to 2022, I was also involved with the Warwick Basketball Club, taking different positions as the years go by (Charity Officer 2018-2019, Men's Teams Captain 2020-2021, Advisor to the Executive Commitee 2021-2022). Additionally, I was a Warwick Sport Activator, encouraging other students to be more active, by running casual, inclusive and beginner friendly basketball sessions.
My growing experience in data manipulation has strengthened my interest in sport data science, especially linked to basketball. On the side, I am familiarising myself with new analytic tools more specialised towards sports analytics (Coursera course if interested). Some of my personal side projects include trying to predict the winning team of future basketball seasons according to old data, or predicting future MVP/ROY according to archival data.

Research

A full publication list can be found here. Below are some of my main current/past research projects.

Debris discs

JWST/MIRI coronagraphic observations of gap-carving planets (Bendahan-West et al., under review) We are using JWST/MIRI coronagraphic observations as part of program GO1668 to search for planets sculpting gaps in three exoKuiper belts: HD92945, HD107146, and HD206893. The observed gapped structures suggest the presence of unseen planets carving a gap through direct clearing or resonant planet-disc interactions. By combining JWST observations with archival data and astrometric constraints, we aim to constrain the planetary architecture responsible for these rare disc structures.

Scattered light disc imaging with JWST/NIRCam coronagraphy (Lazzoni, Bendahan-West et al., 2025) We present the first JWST/NIRCam coronagraphic observations of the HD 92945 debris disc at 2 and 4.4 μm. The disc shows a broad, inclined structure with a gap at ~80 au and a prominent brightness asymmetry in the southwestern inner ring—consistent across multiple wavelengths and epochs, including previous ALMA and HST observations. While no planetary companions are directly detected, our contrast limits exclude Jupiter-mass planets beyond 20-40 au and rule out a single distant planet as the source of Gaia's astrometric signal. Combined with the observed disc features, our results support a scenario where one or more sub-Jupiter planets interior to 20 au dynamically sculpt the disc through secular resonances, explaining the gap, asymmetry, and astrometric acceleration.

Exocomets

Quantifying spectroscopic Ca II exocomet transit occurrence in two decades of HARPS data (Bendahan-West et al. 2025) As part of my Masters, we developed a pipeline that searches for signs of exocomet transits in spectroscopy data. Being guided by the multiple exocomet transits detected around the archetypal star Beta Pictoris, exocomets can be identified by transient absorption features in specific atomic species, such as the commonly used ionised Calcium doublet. We aimed to overcome previous sample selection biases, and use the entire HARPS archive to build a large and diverse sample of stars. Ultimately, we estimate the occurrence rate of exocomet transits in HARPS and determined any trends in exocomet host stars.

Self-Organising Map (Summer project) Project supervisors: Grant Kennedy, Paul Strøm, David Brown
This summer project introduced me to an unsupervised Machine Learning classification algorithm called a Self-Organising Map (SOM) that we used to classify stellar spectra according to their different spectral profiles. This was an attempt to reduce the number of false positive detections in our search for exocomet transits. The main idea is that stars showing similar features (e.g. variable stellar activity), would be classified together, providing an easier method to identify and filter specific sources of false positive exocomet detections.

Contact

Feel free to email me, I am more than happy to collaborate!

Email: rb941[at]exeter.ac.uk

Address:
Physics Building, Streatham Campus,
University of Exeter, Stocker Road, Exeter EX4 4QL, UK

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Curriculum Vitae