2021ApJ...920...22S

The radial velocity study by Donati et al. (2016) reported the detection of a close-in giant planet in a 4.93 day orbit around the ∼2 Myr old weak-lined T Tauri star V830 Tau. Because of the stringent timescale constraints that a very young host star like V830 Tau would place on hot-Jupiter formation models and inward-migration mechanisms, independent confirmation of the planet's existence is needed but so far has not been obtained. We present new Chandra X-ray observations of V830 Tau. The Chandra observations in combination with previous XMM-Newton observations reveal strong, variable X-ray emission with an X-ray luminosity spanning the range log L_x = 30.10-30.87 erg s^–1. Chandra High Energy Transmission Grating spectra show emission lines formed over a range of plasma temperatures from ∼4 MK (Ne IX) to ∼16 MK (S XV). At the separation of the reported planet (0.057 au) the X-ray flux is ∼10⁶-10⁷ times greater than the Sun's X-ray flux at Jupiter. We provide estimates of the X-ray ionization and atmospheric heating rates at the planet's separation and identify areas of uncertainty that will need to be addressed in any future atmospheric models.