Chandra X-ray Observations of V830 Tau: A T Tauri Star Hosting an Evanescent Planet

TL;DR

This study presents new X-ray observations of the young star V830 Tau, providing insights into its high-energy environment and implications for the potential atmosphere of its proposed close-in giant planet.

Contribution

It offers the first detailed X-ray spectral analysis of V830 Tau and assesses the star's X-ray flux impact on the planet's atmosphere, aiding understanding of planet-star interactions.

Findings

V830 Tau exhibits strong, variable X-ray emission with luminosity log Lx = 30.10 - 30.87 ergs/s.

X-ray spectra indicate plasma temperatures from ~4 MK to ~16 MK.

X-ray flux at the planet's orbit is 10^6 - 10^7 times that of the Sun at Jupiter.

Abstract

A radial velocity study by Donati et al. (2016) reported the detection of a close-in giant planet in a 4.93 d 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 Lx = 30.10 - 30.87 ergs/s. Chandra High Energy Transmission Grating (HETG) 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 ~10$^{6}$ - 10$^{7}$ 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.