Supervision

Stellar magnetism plays a fundamental role from the birth of stars to their death, influencing the evolution of stars of all masses. Magnetic fields regulate angular momentum transport, thereby controlling stellar rotation and the internal dynamo. They govern chromospheric and coronal activity, producing flares and stellar winds that sculpt the circumstellar environment. For exoplanets orbiting a magnetic star, this magnetism determines atmospheric erosion by stellar wind and impacts their potential habitability.

High-resolution spectroscopy and spectropolarimetry are the most powerful tools we have for the direct detection and characterization of stellar magnetic fields through the Zeeman effect. These techniques measure the splitting and polarization of spectral lines induced by magnetic fields, providing both field strength and topology. Instruments like ESPaDOnS, Neo-Narval, SPIRou, HARPSpol, CRIRES+, PEPSI have revolutionized stellar magnetism studies across optical and near-infrared wavelengths. Combined with Zeeman-Doppler imaging, spectropolarimetry enables the mapping of the surface magnetic field.

One of these instruments, HARPSpol, has been in operation since 2011 at the 3.6-meter Telescope at the European Southern Observatory, La Silla, Chile. We have recently re-reduced all of the data taken with the instrument, and incorporated it in the PolarBase database. A significant portion of this data has not been explored or published, and we believe that there are very interesting datasets waiting to be analyzed.

For this project, we propose the following

1. Develop data-mining tools to explore the data and connect to various databases to gain insights on the datasets. Connecting with databases such as Telbib, Simbad, Vizier, we will investigate which datasets have been published, and find stellar parameters for all the stars observed. We will select the most promising data for analysis
2. We will analyse the polarized spectra of potentially interesting datasets and attempt to detect magnetic field signatures. If we obtain magnetic field detections, we will characterize the magnetic field, either by computing mean field values, or we will map the magnetic field if we have good enough observations.
3. We will make use of the vast number of stellar objects observed so far with HARPSpol to explore potential magnetic trends across the Hertzsprung-Russell diagram that have not been highlighted with smaller stellar samples.

Understanding exoplanetary systems is crucial for addressing fundamental questions about planetary formation, evolution, and habitability. Magnetic fields play a key role in shielding planetary atmospheres from stellar winds and cosmic radiation, potentially determining whether life can emerge and persist. However, despite thousands of confirmed exoplanets, we have not yet detected directly an exoplanetary magnetic field.

On the one hand, radio observations attempt to detect maser emissions, analogous to Jupiter's auroral radio emissions. While promising, these indirect techniques have yielded ambiguous results and require strong assumptions about planetary magnetic field configurations.

On the other hand, high-resolution near-infrared spectropolarimetry offers the most direct path to detecting exoplanetary magnetic fields. The Zeeman effect splits and polarizes spectral lines in the presence of a magnetic field, producing circular polarization signatures (Stokes V) proportional to the field strength. If a Stokes V signal is detected, it is a clear and direct detection of a magnetic field.

High-resolution spectropolarimeters (state-of-the-art instrument installed at the largest telescope such as the Canada-France-Hawaii Telescope or the Very Large Telescope) can resolve these signatures. The near-infrared domain is particularly advantageous: cooler stars and giant planets emit predominantly at these wavelengths.

This internship focuses on analyzing transit observations which we have obtained with SPIRou at the Canada-France-Hawaii Telescope and CRIRES+ at ESO's Very Large Telescope. You will help develop specialized data reduction pipelines to extract circular polarization signals during exoplanet transits. We aim to isolate the planetary magnetic field contribution. Success would constitute the first direct detection of an exoplanetary magnetic field, opening a new observational window into exoplanet science.