The MOPYS project: A survey of 70 planets in search of extended He i and H atmospheres. No evidence of enhanced evaporation in young planets

Abstract

During the first billion years of their life, exoplanet atmospheres are modified by different atmospheric escape phenomena that can strongly affect the shape and morphology of the exoplanet itself. These processes can be studied with Lyalpha , Halpha , and/or He i triplet observations. We present high-resolution spectroscopy observations from CARMENES and GIARPS checking for He i and Halpha signals in 20 exoplanetary atmospheres: V1298\,Tau\,c, K2-100\,b, HD\,63433\,b, HD\,63433\,c, HD\,73583\,b, HD\,73583\,c, K2-77\,b, TOI-2076\,b, TOI-2048\,b, HD\,235088\,b, TOI-1807\,b, TOI-1136\,d, TOI-1268\,b, TOI-1683\,b, TOI-2018\,b, MASCARA-2\,b, WASP-189\,b, TOI-2046\,b, TOI-1431\,b, and HAT-P-57\,b. We report two new high-resolution spectroscopy He i detections for TOI-1268\,b and TOI-2018\,b, and a Halpha detection for TOI-1136\,d. Furthermore, we detect hints of He i for HD\,63433\,b, and Halpha for HD\,73583\,b and c, which need to be confirmed. The aim of the Measuring Out-flows in Planets orbiting Young Stars (MOPYS) project is to understand the evaporating phenomena and test their predictions from the current observations. We compiled a list of 70 exoplanets with He i and/or Halpha observations, from this work and the literature, and we considered the He i and Halpha results as proxy for atmospheric escape. Our principal results are that 0.1--1Gyr planets do not exhibit more He i or Halpha detections than older planets, and evaporation signals are more frequent for planets orbiting sim 1--3\,Gyr stars. We provide new constraints to the cosmic shoreline, the empirical division between rocky planets and planets with atmosphere, by using the evaporation detections and we explore the capabilities of a new dimensionless parameter He /R_ Hill $, to explain the He i triplet detections. Furthermore, we present a statistically significant upper boundary for the He i triplet detections in the $T_ eq $ versus $ p $ parameter space. Planets located above that boundary are unlikely to show He i absorption signals.