The GAPS Programme at TNG

LIV. A He I survey of close-in giant planets hosted by M-K dwarf stars with GIANO-B^★

¹ INAF – Osservatorio Astrofisico di Torino, Via Osservatorio 20, 10025, Pino Torinese, Italy
e-mail: gloria.guilluy@inaf.it
² INAF – Osservatorio Astronomico di Palermo, Piazza del Parlamento, 1, 90134 Palermo, Italy
³ University of Palermo, Department of Physics and Chemistry – Emilio Segrè, Via Archirafi 36, Palermo, Italy
⁴ DISAT, Università degli Studi dell'Insubria, Via Valleggio 11, 22100 Como, Italy
⁵ INAF – Osservatorio Astronomico di Brera, Via E. Bianchi 46, 23807 Merate, Italy
⁶ Space Research Institute, Austrian Academy of Sciences, Schmiedlstrasse 6, 8042 Graz, Austria
⁷ INAF – Osservatorio Astrofisico di Catania, Via S. Sofia 78, 95123 Catania, Italy
⁸ Fundación Galileo Galilei-INAF, Rambla José Ana Fernandez Pérez 7, 38712 Breña Baja, TF, Spain
⁹ INAF – Osservatorio Astronomico di Roma, Via Frascati 33, 00078 Monte Porzio Catone, Italy
¹⁰ INAF – Osservatorio Astronomico di Trieste, Via Tiepolo 11, 34143 Trieste
¹¹ Instituto de Astrofísica de Canarias (IAC), Calle Vía Láctea s/n, 38200 La Laguna, Tenerife, Spain
¹² Departamento de Astrofísica, Universidad de La Laguna (ULL), 38206 La Laguna, Tenerife, Spain
¹³ INAF – Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio 5, 35122 Padova, Italy
¹⁴ Dipartimento di Fisica e Astronomia Galileo Galilei, Università di Padova, Vicolo dell’Osservatorio 3, 35122 Padova, Italy
¹⁵ Department of Physics, University of Rome “Tor Vergata”, Via della Ricerca Scientifica 1, 00133 Roma, Italy
¹⁶ Max Planck Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany
¹⁷ INAF – Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy

Received: 18 December 2023
Accepted: 1 March 2024

Abstract

Context. Atmospheric escape plays a fundamental role in shaping the properties of exoplanets. The metastable near-infrared (nIR) helium triplet at 1083.3 nm (He I) is a powerful proxy of extended and evaporating atmospheres.

Aims. We used the GIARPS (GIANO-B + HARPS-N) observing mode of the Telescopio Nazionale Galileo to search for He I absorption in the upper atmospheres of five close-in giant planets hosted by the K and M dwarf stars of our sample, namely WASP-69 b, WASP-107 b, HAT-P-11 b, GJ 436 b, and GJ 3470 b.

Methods. We focused our analysis on the nIR He I triplet, performing high-resolution transmission spectroscopy by comparing the in-transit and out-of-transit observations. In instances where nightly variability in the He I absorption signal was identified, we investigated the potential influence of stellar magnetic activity on the planetary absorption signal by searching for variations in the Hα transmission spectrum.

Results. We spectrally resolve the He I triplet and confirm the published detections for WASP-69 b (3.91 ± 0.22%, 17.6σ), WASP-107 b (8.17_−0.76^+0.80%, 10.5σ), HAT-P-11 b (1.36 ± 0.17%, 8.0σ), and GJ 3470 b (1.75_−0.36^+0.39%, 4.7σ). We do not find evidence of extra absorption for GJ 436 b. We observe night-to-night variations in the He I absorption signal for WASP-69 b, associated with variability in Hα, which likely indicates the influence of pseudo-signals related to stellar activity. Additionally, we find that the He I signal of GJ 3470 b originates from a single transit observation, thereby corroborating the discrepancies found in the existing literature. An inspection of the Hα line reveals an absorption signal during the same transit event.

Conclusions. By combining our findings with previous analyses of GIANO-B He I measurements of planets orbiting K dwarfs, we explore potential trends with planetary and stellar parameters that are thought to affect the absorption of metastable He I. Our analysis is unable to identify clear patterns, thus emphasising the necessity for additional measurements and the exploration of potential additional parameters that may be important in controlling He I absorption in planetary upper atmospheres.