E. Gaidos, H. Parviainen, E. Esparza-Borges, A. Fukui, K. Isogai, K. Kawauchi, J. de Leon, M. Mori, F. Murgas, N. Narita, E. Palle, N. Watanabe
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引用次数: 0
Abstract
Context. Rocky planets on ultra-short period orbits can have surface magma oceans and rock-vapour atmospheres in which dust can condense. Observations of that dust can inform us about the composition and surface conditions on these objects.Aims. We constrained the properties and long-term (decade) behaviour of the transiting dust cloud from the evaporating planet K2-22b.Methods.We observed K2-22b around 40 predicted transits with MuSCAT ground-based multi-optical channel imagers, and complemented these data with long-term monitoring by the ground-based ATLAS (2018-2024) and space-based TESS (2021–2023) surveys.Results. We detected signals during 7 transits, none of which showed significant wavelength dependence. The expected number of MuSCAT-detected transits is ≥22, indicating a decline in mean transit depth since the K2 discovery observations in 2014.Conclusions. The lack of a significant wavelength dependence indicates that dust grains are large or the cloud is optically thick. Long-term trends of depth could be due to a magnetic cycle on the host star or to overturn of the planet’s dayside surface magma ocean. The possibility that K2-22b is disappearing altogether is ruled out by the stability of the transit ephemeris against non-gravitational forces, which constrains the mass to be at least comparable to Ceres.
期刊介绍:
Astronomy & Astrophysics is an international Journal that publishes papers on all aspects of astronomy and astrophysics (theoretical, observational, and instrumental) independently of the techniques used to obtain the results.