H-alpha and Ca ii Infrared Triplet Variations During a Transit of the 23 Myr Planet V1298 Tau c

Adina D Feinstein,Marshall C Johnson,Jacob L Bean,John H Livingston,Trevor J David,Michael A Gully-Santiago,Rodrigo Luger,Benjamin T Montet

doi:10.3847/1538-3881/ac1f24

Abstract

Abstract Young transiting exoplanets (<100 Myr) provide crucial insight into atmospheric evolution via photoevaporation. However, transmission spectroscopy measurements to determine atmospheric composition and mass loss are challenging due to the activity and prominent stellar disk inhomogeneities present on young stars. We observed a full transit of V1298 Tau c, a 23 Myr, 5.59 R ⊕ planet orbiting a young K0-K1.5 solar analog with GRACES on Gemini North. We were able to measure the Doppler tomographic signal of V1298 Tau c using the Ca ii infrared triplet (IRT) and find a projected obliquity of λ = 5° ± 15°. The tomographic signal is only seen in the chromospherically driven core of the Ca ii IRT, which may be the result of star-planet interactions. Additionally, we find that excess absorption of the Hα line decreases smoothly during the transit. While this could be a tentative detection of hot gas escaping the planet, we find this variation is consistent with similar timescale observations of other young stars that lack transiting planets over similar timescales. We show this variation can also be explained by the presence of starspots with surrounding facular regions. More observations both in and out of the transits of V1298 Tau c are required to determine the nature of the Ca ii IRT and Hα line variations.

Highlights

The tomographic signal is only seen in the chromospherically driven core of the Ca ii infrared triplet (IRT), which may be the result of star-planet interactions
Because we found our spectra to show little variation over the night, we could not use all spectral features to extract a Rossiter-McLaughlin or Doppler tomographic signal
Of the Fraunhofer lines checked, including the Mg i triplet at 517 nm, and Na D1 and D2 (Figure 4), the tomographic signal was only seen in the Ca ii IRT at 849.8, 854.2, and 866.2 nm

Summary

Introduction

Close-in transiting exoplanets have brought into quesas < 100 Myr) has grown to approximately a dozen tion the mechanisms in which they get there. These planets are key to insights into different migratory paths. A low-obliquity understanding planetary migration, atmospheric evoluhints at a smooth disk migration history All independent studies have measured a low obliquity (Addison et al 2020; Hirano et al 2020; Martioli et al 2020; Palle et al 2020), suggesting the planet formed beyond the ice-line within the protoplanetary disk and experienced a smooth migration inward

Results

Discussion

Conclusion