Almenara, J. M.; Bonfils, X.; Forveille, T.; Astudillo-Defru, N.; Ciardi, D. R.; Schwarz, R. P.; Collins, K. A.; Cointepas, M.; Lund, M. B.; Bouchy, F.; Charbonneau, D.; Díaz, R. F.; Delfosse, X.; Kidwell, R. C.; Kunimoto, M.; Latham, D. W.; Lissauer, J. J.; Murgas, F.; Ricker, G.; Seager, S.; Vezie, M.; Watanabe, D.
Astronomy and Astrophysics
The Transiting Exoplanet Survey Satellite mission identified a deep and asymmetric transit-like signal with a periodicity of 4.5 days orbiting the M4 dwarf star TOI-3884. The signal has been confirmed by follow-up observations collected by the ExTrA facility and Las Cumbres Observatory Global Telescope, which reveal that the transit is chromatic. The light curves are well modelled by a host star having a large polar spot transited by a 6-RE planet. We validate the planet with seeing-limited photometry, high-resolution imaging, and radial velocities. TOI-3884 b, with a radius of 6.00 ± 0.18 RE, is the first sub-Saturn planet transiting a mid-M dwarf. Owing to the host star's brightness and small size, it has one of the largest transmission spectroscopy metrics for this planet size and becomes a top target for atmospheric characterisation with the James Webb Space Telescope and ground-based telescopes.
Exoplanets and Astrobiology
The search for life in the universe has been driven by recent discoveries of planets around other stars (known as exoplanets), becoming one of the most active fields in modern astrophysics. The growing number of new exoplanets discovered in recent years and the recent advance on the study of their atmospheres are not only providing new valuable