088287

Photoevaporative mass loss is key to sculpting the properties of short period transiting exoplanets comma yet current models have large uncertainties. One of the biggest sources of uncertainty is the high-energy openParX-ray and extreme UVclosePar spectrum of the star. Stellar EUV cannot be measured due to interstellar absorption comma and must be inferred from the X-ray luminosity. We propose a survey to measure the X-ray spectra of four young comma active stars hosting small openPar< 3.5 R_EarthclosePar planets. This regime is the most critical for understanding exoplanet demographics comma and our targets are the most observationally favorable for detecting exospheric absorption. The spectra measured by XMM-Newton will be crucial in understanding photoevaporation from these exceptional planets.