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

Publication date: 
Main author: 
Palle, E.
IAA authors: 
Lampón, M.;López-Puertas, M.;Lara, L. M.;Amado, P. J.
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.
Astronomy and Astrophysics
Publication type: 
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<SUP>3</SUP>S) absorption. On one of the nights, the He I region was heavily contaminated by OH<SUP>-</SUP> 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<SUP>3</SUP>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<SUB>p</SUB>(λ)/R<SUB>p</SUB> = 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<SUP>3</SUP>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<SUP>10</SUP> g s<SUP>-1</SUP> for T = 6000 K to 10 × 10<SUP>10</SUP> g s<SUP>-1</SUP> 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.
ADS Bibcode: 
planetary systems;planets and satellites: atmospheres;planet-star interactions;planets and satellites: general;planets and satellites: individual: GJ 3470b;Astrophysics - Earth and Planetary Astrophysics;Astrophysics - Solar and Stellar Astrophysics