Zodiacal exoplanets in time – XI. The orbit and radiation environment of the young M dwarf-hosted planet K2-25b

ABSTRACT M dwarf stars are high-priority targets for searches for Earth-size and potentially Earth-like planets, but their planetary systems may form and evolve in very different circumstellar environments than those of solar-type stars. To explore the evolution of these systems, we obtained transit...

Full description

Saved in:
Bibliographic Details
Published in:Monthly notices of the Royal Astronomical Society. Letters 2020-10, Vol.498 (1), p.L119-L124
Main Authors: Gaidos, E, Hirano, T, Wilson, D J, France, K, Rockcliffe, K, Newton, E, Feiden, G, Krishnamurthy, V, Harakawa, H, Hodapp, K W, Ishizuka, M, Jacobson, S, Konishi, M, Kotani, T, Kudo, T, Kurokawa, T, Kuzuhara, M, Nishikawa, J, Omiya, M, Serizawa, T, Tamura, M, Ueda, A, Vievard, S
Format: Article
Language:English
Citations: Items that this one cites
Items that cite this one
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:ABSTRACT M dwarf stars are high-priority targets for searches for Earth-size and potentially Earth-like planets, but their planetary systems may form and evolve in very different circumstellar environments than those of solar-type stars. To explore the evolution of these systems, we obtained transit spectroscopy and photometry of the Neptune-size planet orbiting the ≈650-Myr-old Hyades M dwarf K2-25. An analysis of the variation in spectral line shape induced by the Doppler ‘shadow’ of the planet indicates that the planet’s orbit is closely aligned with the stellar equator ($\lambda =-1.7_{-3.7}^{+5.8}$ deg), and that an eccentric orbit found by previous work could arise from perturbations by another planet on a coplanar orbit. We detect no significant variation in the depth of the He i line at 1083 nm during transit. A model of atmospheric escape as an isothermal Parker wind with a solar composition shows that this non-detection is not constraining compared to escape rate predictions of ∼0.1 M⊕  Gyr−1; at such rates, at least several Gyr are required for a Neptune-like planet to evolve into a rocky super-Earth.
ISSN:1745-3925
1745-3933
DOI:10.1093/mnrasl/slaa136