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Thesis defense by Neda Heidari

29 November 2022 à 13h00 - 17h00

“Overcoming the stellar activity impact on exoplanet detection and

The defense will be held in English. Please find below the Ph.D. thesis abstract and the jury

Lien zoom:

Low-mass planets, with a mass of lower than 30 Earth masses, have an
extraordinarily diverse range in terms of compositions. Their bulk
density, derived by combining radial velocity and photometric data,
ranges from massive rocky super-Earth with iron‐rich cores to
low-density objects with deep gaseous atmospheres. The extremely diverse
composition of these planets raises several questions regarding theories of
atmospheric loss and planetary formation. Our ability to answer these
questions is currently limited by the low number of low-mass planets for
which fundamental properties have been accurately characterized. The
goal of this thesis is to contribute to the study of the diversity of
low-mass planets’ composition, by increasing the sample of precisely
characterized low-mass planets, and making the link between the
observations and the
formation paths of these bodies. More specifically, this thesis focuses on
overcoming two main challenges: 1) instrumental limitations, to improve
radial velocity data reduction and processing to facilitate the
detection of low-mass planets, and 2) detecting low-mass planets and
characterizing them.

When using the radial velocity method, a highly precise data reduction
system, that can
treat the possible systematic sources of errors, is required to reach
the instrumental limit of detecting low-mass planets. Therefore, first I
focused on troubleshooting and improving the SOPHIE Data Reduction
Software (DRS). These attempts led to a great improvement of 22 cm/s in
mean RVs RMS, and 18.57 m/s in mean FWHM RMS. Then, I faced the
challenge of low-mass planet detection and accurately characterizing
them. I carried out the photometry and radial velocity analysis of the
SOPHIE SP1 targets, a dedicated program to probe low-mass planet
detections. These attempts resulted in the discovery and full
characterization of two transiting low-mass planets and several other
candidates. The techniques developed and the results obtained in this
thesis will greatly contribute to the accurate detection and
characterization of planets by SOPHIE. Discovered
low-mass planets will contribute to a deeper understanding of the
low-mass planet populations.


Jury members:

Magali Deleuil (President of the jury, LAM)
Anne-Marie Lagrange (reviewer, LESIA)
Claude Catala (reviewer, LESIA)
Lionel BIGOT (examiner, OCA)
Monika Lendl (examiner, Geneva Observatory)
Isabelle Boisse (Ph.D. supervisor, LAM)
Farrokh Vakili (Ph.D. supervisor, OCA).


29 November 2022
13h00 - 17h00
Event Category:


Amphi du LAM