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arXiv · 2305.03255

A search for stellar siblings of the ~ 200 Myr TOI-251b planetary system

Qinghui Sun·Sharon Xuesong Wang·Andrew W. Mann·Benjamin M. Tofflemire·Adam L. Kraus·Tianjun Gan·Madyson G. Barber
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Abstract

Young planets (< 1 Gyr) are helpful for studying the physical processes occurring at the early stage of planet evolution. TOI-251 b is a recently discovered sub-Neptune orbiting a young G dwarf, which has an imprecise age estimation of 40-320 Myr. We select TOI-251 sibling candidates based on kinematics and spatial proximity to TOI-251, and further use the color-magnitude diagram (CMD) to refine the list and to compare to multiple open clusters. We report stellar rotational period for 321 sibling candidates in a 50 pc radius around TOI-251 by analyzing their stellar light curves, and find a color - rotational period sequence that lie in between the Group X (300 Myr) and Pleiades (120 Myr) members, suggesting an age ~ 200 Myr. A quantitative age analysis by using gyrochronology relations give 204 $\pm$ 45 Myr, consistent with the average Li-age of selected siblings (238 $\pm$ 38 Myr) and the Gaia variability age (193$^{102}_{-54}$ Myr). The detection fraction of comoving candidates that have short rotational period is 68.1%, much higher than the typical value in the field (14% - 16% from Kepler). The overdensity of young stars and consistency in age of stellar siblings suggest a potential young association candidate in the Pheonix-Grus constellation. Though TOI-251 b has a radius larger than most of its field-age counterparts, we are uncertain whether TOI-251 is inflated due to a lack of knowledge on the planet's mass.

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Qinghui Sun, Sharon Xuesong Wang, Andrew W. Mann, Benjamin M. Tofflemire, Adam L. Kraus, Tianjun Gan, Madyson G. Barber. 2023-05-05. A search for stellar siblings of the ~ 200 Myr TOI-251b planetary system. https://doi.org/10.3847/1538-4357%2Facd346

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