H-alpha and Ca II Infrared Triplet Variations During a Transit of the 23 Myr Planet V1298 Tau c. (arXiv:2107.01213v2 [astro-ph.EP] UPDATED)

H-alpha and Ca II Infrared Triplet Variations During a Transit of the 23 Myr Planet V1298 Tau c. (arXiv:2107.01213v2 [astro-ph.EP] UPDATED)
<a href="http://arxiv.org/find/astro-ph/1/au:+Feinstein_A/0/1/0/all/0/1">Adina D. Feinstein</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Montet_B/0/1/0/all/0/1">Benjamin T. Montet</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Johnson_M/0/1/0/all/0/1">Marshall C. Johnson</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bean_J/0/1/0/all/0/1">Jacob L. Bean</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+David_T/0/1/0/all/0/1">Trevor J. David</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Gully_Santiago_M/0/1/0/all/0/1">Michael A. Gully-Santiago</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Livingston_J/0/1/0/all/0/1">John H. Livingston</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Luger_R/0/1/0/all/0/1">Rodrigo Luger</a>

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$R_oplus$
planet orbiting a young K0-K1.5 solar analogue 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 $lambda = 5^circ
pm 15^circ$. 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 H-alpha 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 H-alpha line variations.

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$R_oplus$
planet orbiting a young K0-K1.5 solar analogue 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 $lambda = 5^circ
pm 15^circ$. 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 H-alpha 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 H-alpha line variations.

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