GIARPS explores the enigmatic nature of TOI-5398 b atmospheric signal

A recent study within the GAPS collaboration (Global Architecture of Planetary Systems ) used two of the instruments permanently mounted on Telescopio Nazionale Galileo to study the atmospheres of the extrasolar planet TOI-5398 b.

Namely, HARPS-N (High Accuracy Radial velocity Planet Searcher in North hemisphere) and GIANO-B (near-IR high-resolution echelle spectrograph of the TNG) were used in the GIARPS configuration to characterize the atmospheric properties of TOI-5398 b, a warm Saturn with a 10.59-day orbit around a young (650 Myr) G-type star. The system also hosts a smaller inner planet, TOI-5398 c, with a 4.77-day orbit. Both planets are ideal for atmospheric studies due to their proximity to the host star, which drives strong photo-evaporation, especially in planet b, whose strong emission lines detected in its atmosphere by transmission spectroscopy makes it a prime target.

Atmospheric characterization is key to understanding exoplanetary systems, offering insights into the planets current and past conditions. By analyzing key lines like H alpha and the He I triplet, it is possible to trace the evolution of planets through atmospheric photo-evaporation. In this context, the detection of Hα and He I triplets, as well as the Na I doublet, contributed valuable data to confirm theoretical predictions regarding atmospheric escape in exoplanets. This research also offered a clearer picture of the height distribution of atmospheric elements, showing that He I and Na I lie in outer atmospheric layers, while Hα is more centrally located.

The study's novelty lies in confirming these features in a warm Saturn-like planet rather than an ultra-hot Jupiter. Additionally, the detection of the Na I doublet in this relatively cold atmosphere (947 K) adds to the knowledge base of atmospheric compositions in cooler exoplanets. The combination of He I and Hα in a single system is rare and helps further to substantiate models predicting photo-evaporation effects.

Useful links

Link to the paper: https://arxiv.org/abs/2410.15917
Information about the planetary system: https://www.media.inaf.it/2024/02/13/il-piu-giovane-sistema-multi-planetario-compatto/

Simulated absorption profiles for both planets changing the He/H number abundance. The green line corresponds to the He I observed signal with 1σ error bars. The blue and red bands correspond to the simulations obtained for the two planets, varying the X-ray luminosity by a factor of two. As it can be seen, according to the simulations the observed signal cannot arise from planet c. More information in the paper.

Artistic image of TOI5398b and its star. Credits: Nasa

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Home General Info News Telescope & Instruments Observing Time Allocations & Schedules Publications Seminars Weather Webcam Outreach Gallery Links	GIARPS explores the enigmatic nature of TOI-5398 b atmospheric signal A recent study within the GAPS collaboration (Global Architecture of Planetary Systems ) used two of the instruments permanently mounted on Telescopio Nazionale Galileo to study the atmospheres of the extrasolar planet TOI-5398 b. Namely, HARPS-N (High Accuracy Radial velocity Planet Searcher in North hemisphere) and GIANO-B (near-IR high-resolution echelle spectrograph of the TNG) were used in the GIARPS configuration to characterize the atmospheric properties of TOI-5398 b, a warm Saturn with a 10.59-day orbit around a young (650 Myr) G-type star. The system also hosts a smaller inner planet, TOI-5398 c, with a 4.77-day orbit. Both planets are ideal for atmospheric studies due to their proximity to the host star, which drives strong photo-evaporation, especially in planet b, whose strong emission lines detected in its atmosphere by transmission spectroscopy makes it a prime target. Atmospheric characterization is key to understanding exoplanetary systems, offering insights into the planets current and past conditions. By analyzing key lines like H alpha and the He I triplet, it is possible to trace the evolution of planets through atmospheric photo-evaporation. In this context, the detection of Hα and He I triplets, as well as the Na I doublet, contributed valuable data to confirm theoretical predictions regarding atmospheric escape in exoplanets. This research also offered a clearer picture of the height distribution of atmospheric elements, showing that He I and Na I lie in outer atmospheric layers, while Hα is more centrally located. The study's novelty lies in confirming these features in a warm Saturn-like planet rather than an ultra-hot Jupiter. Additionally, the detection of the Na I doublet in this relatively cold atmosphere (947 K) adds to the knowledge base of atmospheric compositions in cooler exoplanets. The combination of He I and Hα in a single system is rare and helps further to substantiate models predicting photo-evaporation effects. Useful links Link to the paper: https://arxiv.org/abs/2410.15917 Information about the planetary system: https://www.media.inaf.it/2024/02/13/il-piu-giovane-sistema-multi-planetario-compatto/ Simulated absorption profiles for both planets changing the He/H number abundance. The green line corresponds to the He I observed signal with 1σ error bars. The blue and red bands correspond to the simulations obtained for the two planets, varying the X-ray luminosity by a factor of two. As it can be seen, according to the simulations the observed signal cannot arise from planet c. More information in the paper. Artistic image of TOI5398b and its star. Credits: Nasa
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