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arXiv · 2302.01479

Absence of extended atmospheres in low-mass star radius-gap planets GJ 9827 b, GJ 9827 d and TOI-1235 b

Vigneshwaran Krishnamurthy·Teruyuki Hirano·Eric Gaidos·Bunei Sato·Ravi Kopparapu·Thomas Barclay·Katherine Garcia-Sage·Hiroki Harakawa·Klaus Hodapp·Shane Jacobson·Mihoko Konishi·Takayuki Kotani·Tomoyuki Kudo·Takashi Kurokawa·Masayuki Kuzuhara·Eric Lopez·Jun Nishikawa·Masashi Omiya·Joshua E. Schlieder·Takuma Serizawa·Motohide Tamura·Akitoshi Ueda·Sebastien Vievard
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Abstract

\textit{Kepler} showed a paucity of planets with radii of 1.5 - 2 $\mathrm R_{\oplus}$ around solar mass stars but this radius-gap has not been well studied for low-mass star planets. Energy-driven escape models like photoevaporation and core-powered mass-loss predict opposing transition regimes between rocky and non-rocky planets when compared to models depicting planets forming in gas-poor environments. Here we present transit observations of three super-Earth sized planets in the radius-gap around low-mass stars using high-dispersion InfraRed Doppler (IRD) spectrograph on the Subaru 8.2m telescope. The planets GJ 9827 b and d orbit around a K6V star and TOI-1235 b orbits a M0.5 star. We limit any planet-related absorption in the 1083.3 nm lines of triplet He I by placing an upper-limit on the equivalent width of 14.71 mÅ, 18.39 mÅ, and 1.44 mÅ, for GJ 9827 b (99% confidence), GJ 9827 d (99% confidence) and TOI-1235 b (95% confidence) respectively. Using a Parker wind model, we cap the mass-loss at $>$0.25 $\mathrm M_{\oplus}$ Gyr$^{-1}$ and $>$0.2 $\mathrm M_{\oplus}$ Gyr$^{-1}$ for GJ 9827 b and d, respectively (99% confidence), and $>$0.05 $\mathrm M_{\oplus}$ Gyr$^{-1}$ for TOI-1235 b (95\% confidence) for a representative wind temperature of 5000 K. Our observed results for the three planets are more consistent with the predictions from photoevaporation and/or core-powered mass-loss models than the gas-poor formation models. However, more planets in the radius-gap regime around the low-mass stars are needed to robustly predict the atmospheric evolution in planets around low-mass stars.

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Vigneshwaran Krishnamurthy, Teruyuki Hirano, Eric Gaidos, Bunei Sato, Ravi Kopparapu, Thomas Barclay, Katherine Garcia-Sage, Hiroki Harakawa, Klaus Hodapp, Shane Jacobson, Mihoko Konishi, Takayuki Kotani, Tomoyuki Kudo, Takashi Kurokawa, Masayuki Kuzuhara, Eric Lopez, Jun Nishikawa, Masashi Omiya, Joshua E. Schlieder, Takuma Serizawa, Motohide Tamura, Akitoshi Ueda, Sebastien Vievard. 2023-03-17. Absence of extended atmospheres in low-mass star radius-gap planets GJ 9827 b, GJ 9827 d and TOI-1235 b. https://doi.org/10.1093/mnras%2Fstad404

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