High-resolution Spectra and Biosignatures of Earth-like Planets Transiting White Dwarfs

Abstract

Abstract With the first observations of debris disks as well as proposed planets around white dwarfs (WDs), the question of how rocky planets around such stellar remnants can be characterized and probed for signs of life becomes tangible. WDs are similar in size to Earth and have relatively stable environments for billions of years after initial cooling, making them intriguing targets for exoplanet searches and terrestrial planet atmospheric characterization. Their small size and the resulting large planet transit signal allows observations with next-generation telescopes to probe the atmosphere of such rocky planets, if they exist. We model high-resolution transmission spectra for planets orbiting WDs as they cool from 6000 to 4000 K, for (i) planets receiving equivalent irradiation to modern Earth, and (ii) planets orbiting at the distance around a cooling WD that allows for the longest continuous time in the habitable zone. All high-resolution transmission spectra are publicly available online and can be used as a tool to prepare and interpret upcoming observations with the James Webb Space Telescope, the Extremely Large Telescopes, as well as mission concepts like Origins, HabEx, and LUVOIR.