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arXiv · 2506.04440

The Age and High Energy Environment of the Very Young Transiting Exoplanet TOI 1227b

Attila Varga·Joel H. Kastner·Alexander S. Binks·Hans Moritz Guenther·Simon J. Murphy
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Abstract

The mid-M star TOI~1227 hosts among the youngest known transiting exoplanets. We have conducted new X-ray imaging and optical spectroscopic observations of TOI 1227 aimed at ascertaining its age and the influence of its high-energy radiation on the exoplanet, TOI 1227b. We obtained a definitive X-ray detection of TOI 1227 with Chandra/HRC-I, and measured its Li and H$α$ lines using ANU SSO 2.3 m telescope (WiFeS) spectroscopy. Through spatiokinematic, isochronal, and SED-based modeling, we have constrained the age of TOI 1227 as lying between 5 Myr and 12 Myr, with a best estimate of $\sim$8 Myr. In the context of this age, we model the evolution of the transiting exoplanet TOI 1227b, using the X-ray luminosity derived from Chandra HRC-I imaging. Our modeling suggests that TOI 1227b is currently undergoing rapid atmospheric mass loss at rates on the order of $\sim 10^{12}$ g s$^{-1}$. The modeling demonstrates that the exoplanet's predicted future evolution depends sensitively on assumptions for total and core planet mass, highlighting the importance of follow-up observations of the TOI 1227 star-exoplanet system to enable measurements of both planetary mass and mass-loss rate.

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Attila Varga, Joel H. Kastner, Alexander S. Binks, Hans Moritz Guenther, Simon J. Murphy. 2025-06-04. The Age and High Energy Environment of the Very Young Transiting Exoplanet TOI 1227b. https://arxiv.org/abs/2506.04440

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