Radio jobs in France

Organisation/Company CNRS Department Laboratoire d\'Instrumentation et de Recherche en Astrophysique Research Field Astronomy Astronomy » Astrophysics Astronomy » Cosmology Researcher Profile First Stage Researcher (R1) Country France Application Deadline 7 Oct 2025 - 23:59 (UTC) Type of Contract Temporary Job Status Full-time Hours Per Week 35 Offer Starting Date 1 Nov 2025 Is the job funded through the EU Research Framework Programme? Not funded by a EU programme Is the Job related to staff position within a Research Infrastructure? No

The thesis will be co-supervised by Philippe ZARKA (CNRS Research Director at the Paris Observatory, LIRA, Meudon) for the interpretation/modeling/theory of stellar and exoplanetary emissions, and Cyril TASSE (Assistant Astronomer at the Paris Observatory, LUX, Meudon, and at IRISA, Rennes) for the radio interferometry and signal processing. Supervision will include regular progress reviews, a thesis monitoring committee at LIRA, participation in LOFAR and NenuFAR project meetings, SKA conferences, seminars, and doctoral training. In addition to the two complementary supervisors, collaborations are planned with researchers and engineers involved in LOFAR, NenuFAR, and SKA, as well as the rich and diverse French exoplanetary and stellar communities. The thesis opens up opportunities for international collaborations in the context of LOFAR 2.0 (Harish Vedantham et al., ASTRON, Netherlands), MeerKAT, and SKA (Oleg Smirnov et al., SARAO, South Africa). It is funded by LIRA, which also provides optimal support to its doctoral students.

Until the detection of the first exoplanet around a star other than the Sun in 1995, the solar system was our only laboratory for understanding the formation and nature of planets. Thirty years later, more than 6,000 exoplanets have been discovered orbiting around approximately 4,500 stars, and these systems show a rich and unexpected diversity. Most of them have been discovered using radial velocity (RV) and transit methods. The detection of radio emissions from exoplanetary systems could provide a new method for detecting exoplanets, while also providing complementary information that was previously inaccessible, such as magnetic field strength, internal structure and planetary dynamo regimes, rotation period, spin-orbit locking, star-planet interaction energies, and possible constraints on their habitability. Stellar bursts have already been detected in the radio domain at frequencies ≥600 MHz, and originate from complex dynamic or eruptive processes in the atmospheres of stars. Lower radio frequencies allow us to explore outer stellar envelopes, coronal mass ejections (CMEs), and various other acceleration and instability processes. Star-planet interactions and their associated auroral emissions are expected to produce strongly circularly polarized sources at frequencies of around ~100 MHz via the cyclotron maser instability (CMI). However, only the planets in our solar system have been studied in detail in radio waves. CMI produces intense, anisotropically collimated, entirely elliptical or strongly circularly polarized, low-frequency, broadband radio bursts (see (Zarka, 1998) for a review). This thesis aims to deepen our understanding of stellar environments and star-planet interactions by studying their low-frequency radio emissions. Using the LoTSS-wide and LoTSS-deep surveys conducted by LOFAR at 120-165 MHz (Shimwell et al., 2017; Tasse et al., 2021; Shimwell et al., 2022), we will develop advanced methods for detecting and analyzing stellar radio bursts, improving on the approach developed for analyzing the first LoTSS DR1-2 releases. This work will significantly increase the size of the samples studied and better constrain the properties of the emitting stellar populations and the physical mechanisms responsible for these emissions. The arrival of LOFAR 2.0 in 2026 will offer more sensitive observations at lower frequencies, expanding the capabilities for analyzing radio emissions. This work will prepare for the operation of the Square Kilometer Array (SKA) starting around 2030, which will enable advanced synthesis of dynamic spectra, opening up access to even weaker and rarer phenomena. This project thus aims to study a largely unexplored parameter space. This work heralds a new era in the study of star-planet plasma interactions, with major implications for understanding stellar environments, the magnetic fields of exoplanets, and their habitability. Thanks to our newly developed method, which allows us to track very large samples of stellar systems simultaneously from data produced by radio interferometers, we have produced hundreds of thousands of dynamic spectra (in time-frequency) since 2016 from LOFAR data. Two initial articles present promising discoveries: the identification of a population of stars emitting highly circularly polarized radio bursts, some potentially produced by star-planet interactions (Tasse et al., 2025), and the discovery of the first type II stellar burst (Callingham et al., 2025). The proposed thesis aims to deepen this analysis, extend its scope, and overcome the limitations of the preliminary work:

• Analysis of data from the LoTSS-deep survey, which offers much longer integration times (hundreds of hours per pointing, compared to only 8 hours in our preliminary studies), allowing individual systems to be tracked over longer timescales in order to search for long-term variations or periodic signatures in radio emissions.
• Application of our method to the analysis of the second half of the LoTSS-wide data, recently pre-processed (synthesis of images and dynamic spectra), doubling the size of the studied sample and thus offering the opportunity to explore the statistics of low-frequency radio emissions over a much larger population (distribution of the different types of radio bursts detected, identification of the physical mechanisms underlying these emissions).
• Particular attention will be paid to the Kepler fields, which contain thousands of known low-mass planets, and more generally to a dozen fields located in the Galactic plane.
• Finally, it will be possible to analyze the variability of dynamic spectra, in particular to compare them with the most recent physical predictions (Mauduit et al., 2023; Mauduit, 2024), backed by a new database of stellar magnetic fields (and a method for estimating unmeasured fields), in order to identify the laws governing these radio emissions.
• Methodologically, we will study the effect of residual calibration errors by synthesizing dynamic spectra at varying distances from bright sources in the field of view, in order to construct an optimal and effective detection criterion that can be used on other radio telescopes (notably SKA).