A Search for Planetary Metastable Helium Absorption in the V1298 Tau System

Early in their lives, planets endure extreme amounts of ionizing radiation from host stars. For with primordial hydrogen and helium-rich envelopes, this can lead to substantial mass loss. Direct observations atmospheric escape young planetary systems help elucidate critical stage evolution. In work, we search for metastable helium absorption---a tracer tenuous gas escaping atmospheres---during transits three orbiting the solar analogue V1298 Tau. We characterize stellar line using HET/HPF, find that it evolves substantially on timescales days months. The is stable hour-long except one set spectra taken during decay phase a flare, where absoprtion increased time. Utilizing beam-shaping diffuser narrowband filter centered feature, observe four Palomar/WIRC: two partial planet d ($P = 12.4$ days), transit b 24.1$ full c 8.2$ days). do not detect c, no evidence excess absorption b, $\Delta R_\mathrm{b}/R_\star<0.019$ our bandpass. tentative signal R_\mathrm{d}/R_\star 0.0205\pm0.054$, but best-fit model requires (-100$\pm$14 min) transit-timing offset two-month timescale. Nevertheless, data suggest Tau may have high present-day mass-loss rate, making priority target follow-up observations.