The GAPS Programme at TNG

XXIX. No detection of reflected light from 51 Peg b using optical high-resolution spectroscopy^★,★★

¹ INAF – Osservatorio Astrofisico di Catania, Via S.Sofia 78, 95123 Catania, Italy
e-mail: gaetano.scandariato@inaf.it
² INAF – Osservatorio Astronomico di Brera, Via E. Bianchi 46, 23807 Merate, Italy
³ Dipartimento di Fisica e Astronomia Galileo Galilei, Università di Padova, Vicolo dell’Osservatorio 3, 35122 Padova, Italy
⁴ INAF – Osservatorio Astronomico di Roma, Via Frascati 33, 00040 Monte Porzio Catone (RM), Italy
⁵ INAF – Osservatorio Astrofisico di Torino, Via Osservatorio 20, 10025 Pino Torinese, Italy
⁶ INAF – Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio 5, 35122 Padova, Italy
⁷ INAF – Osservatorio Astronomico di Capodimonte, Salita Moiariello 16, 80131 Napoli, Italy
⁸ INAF – Osservatorio Astronomico di Trieste, Via Tiepolo 11, 34143 Trieste, Italy
⁹ Thüringer Landessternwarte Tautenburg, Sternwarte 5, 07778 Tautenburg, Germany
¹⁰ Dipartimento di Fisica G. Occhialini, Università degli Studi di Milano-Bicocca, Piazza della Scienza 3, 20126 Milano, Italy
¹¹ INAF – Osservatorio Astronomico di Palermo, Piazza del Parlamento, 1, 90134 Palermo, Italy
¹² Department of Physics, University of Rome “Tor Vergata”, Via della Ricerca Scientifica 1, 00133 Rome, Italy
¹³ Max Planck Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany
¹⁴ Aix-Marseille Univ, CNRS, CNES, LAM, Marseille, France
¹⁵ INAF – Osservatorio Astrofisico di Arcetri, Largo Enrico Fermi 5, 50125 Firenze, Italy
¹⁶ Dip. di Fisica, Sapienza, Universitá di Roma, Piazzale Aldo Moro, 2, 00185 Roma, Italy
¹⁷ Astronomy Department and Van Vleck Observatory, Wesleyan University, Middletown, CT 06459, USA
¹⁸ Fundación Galileo Galilei – INAF, Rambla José Ana Fernandez Pérez 7, 38712 Breña Baja, TF, Spain
¹⁹ INAF – Osservatorio Astronomico di Cagliari & REM, Via della Scienza, 5, 09047 Selargius CA, Italy

Received: 27 August 2020
Accepted: 17 December 2020

Abstract

Context. The analysis of exoplanetary atmospheres by means of high-resolution spectroscopy is an expanding research field which provides information on the chemical composition, thermal structure, atmospheric dynamics, and orbital velocity of exoplanets.

Aims. In this work, we aim to detect the light reflected by the exoplanet 51 Peg b by employing optical high-resolution spectroscopy.

Methods. To detect the light reflected by the planetary dayside, we used optical High Accuracy Radial velocity Planet Searcher and High Accuracy Radial velocity Planet Searcher for the Northern hemisphere spectra taken near the superior conjunction of the planet, when the flux contrast between the planet and the star is maximum. To search for the weak planetary signal, we cross-correlated the observed spectra with a high signal-to-noise ratio stellar spectrum.

Results. We homogeneously analyze the available datasets and derive a 10⁻⁵ upper limit on the planet-to-star flux contrast in the optical.

Conclusions. The upper limit on the planet-to-star flux contrast of 10⁻⁵ translates into a low albedo of the planetary atmosphere (A_g ≲ 0.05−0.15 for an assumed planetary radius in the range of 1.5−0.9 R_Jup, as estimated from the planet’s mass).