A He I upper atmosphere around the warm Neptune GJ 3470 b

High resolution transit spectroscopy has proven to be a reliable technique for the characterization of the chemical composition of exoplanet atmospheres. Taking advantage of the broad spectral coverage of the CARMENES spectrograph, we initiated a survey aimed at characterizing a broad range of plane...

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Bibliographic Details
Published in:Astronomy and astrophysics (Berlin) 2020-06, Vol.638, p.A61
Main Authors: Palle, E., Nortmann, L., Casasayas-Barris, N., Lampón, M., López-Puertas, M., Caballero, J. A., Sanz-Forcada, J., Lara, L. M., Nagel, E., Yan, F., Alonso-Floriano, F. J., Amado, P. J., Chen, G., Cifuentes, C., Cortés-Contreras, M., Czesla, S., Molaverdikhani, K., Montes, D., Passegger, V. M., Quirrenbach, A., Reiners, A., Ribas, I., Sánchez-López, A., Schweitzer, A., Stangret, M., Zapatero Osorio, M. R., Zechmeister, M.
Format: Article
Language:English
Subjects:
Absorption
Atmospheric models
Chemical composition
Extrasolar planets
Gas giant planets
Light curve
Night
Planetary atmospheres
Planetary systems
Radiative transfer
Signal to noise ratio
Transit
Upper atmosphere
Weather
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Summary:High resolution transit spectroscopy has proven to be a reliable technique for the characterization of the chemical composition of exoplanet atmospheres. Taking advantage of the broad spectral coverage of the CARMENES spectrograph, we initiated a survey aimed at characterizing a broad range of planetary systems. Here, we report our observations of three transits of GJ 3470 b with CARMENES in search of He (2 3 S) absorption. On one of the nights, the He  I region was heavily contaminated by OH − telluric emission and, thus, it was not useful for our purposes. The remaining two nights had a very different signal-to-noise ratio (S/N) due to weather. They both indicate the presence of He (2 3 S) absorption in the transmission spectrum of GJ 3470 b, although a statistically valid detection can only be claimed for the night with higher S/N. For that night, we retrieved a 1.5 ± 0.3% absorption depth, translating into a R p ( λ )∕ R p = 1.15 ± 0.14 at this wavelength. Spectro-photometric light curves for this same night also indicate the presence of extra absorption during the planetary transit with a consistent absorption depth. The He (2 3 S) absorption is modeled in detail using a radiative transfer code, and the results of our modeling efforts are compared to the observations. We find that the mass-loss rate, Ṁ , is confined to a range of 3 × 10 10 g s −1 for T = 6000 K to 10 × 10 10 g s −1 for T = 9000 K. We discuss the physical mechanisms and implications of the He  I detection in GJ 3470 b and put it in context as compared to similar detections and non-detections in other Neptune-size planets. We also present improved stellar and planetary parameter determinations based on our visible and near-infrared observations.
ISSN:0004-6361
1432-0746
DOI:10.1051/0004-6361/202037719