Exoplanets from a High Energy perspective

High energy stellar phenomena, such as stellar flares and UV irradiation, are crucial conditions for planet habitability and suspected to play a role in the atmospheric evolution of rocky planets. UV and X-ray transit measurements can also provide information about atmospheric evaporation and composition. The UM SPICEs group takes a multi-faceted approach to characterizing exoplanets with X-ray and UV observational facilities.

  • How do the high energy properties of the host star affect the evolution of an exoplanet’s atmosphere? Utilizing the X-ray and UV capabilities of the Neil Gehrels Swift Observatory and XMM-Newton, we fill gaps in the available databases of UV and X-ray properties of exoplanet hosting stars and use planet evolutionary codes to characterize the past and future mass loss of these planets (King et al. 2019, 2021).
  • What can we learn from measuring exoplanet transits in the near UV? Measuring UV transits might provide insights into key physical processes shaping exoplanet atmospheres: evaporation, photochemistry in the upper atmosphere, and haze formation. Working to extend the current capabilities of UV enabled telescopes, Swift and XMM-Newton, we have measured NUV transits from HD 189733b, XO-3b, and KELT-3b (King et al. 2021, Corrales et al. 2021). Searching for trends in NUV transit depths provides insight into the physical mechanisms for NUV absorption and their influence on exoplanet demographics. Our group continues to work on statistical and instrument techniques to increase the utility of Swift and XMM-Newton for measuring NUV transits.
  • What is the composition of aerosols in exoplanet atmospheres? Understanding the composition and sizes of photochemically produced hazes and condensates (clouds) provides one of the most difficult challenges for interpreting observations of exoplanet atmospheres. Our latest projects will provide optical properties of new potential aerosol species to the exoplanet community, examine how aerosol signatures in exoplanet transmission spectra can provide insights into atmospheric chemistry and formation scenarios, and determine whether aerosols are responsible for the tentative NUV transit trends observed in Corrales et al. (2021).

Links to papers:

The XUV irradiation and likely atmospheric escape of the super-Earth π Men c
EUV irradiation of exoplanet atmospheres occurs on Gyr time-scales

The near-UV transit of HD 189733b with the XMM-Newton optical monitor
Five New Hot Jupiter Transits Investigated with Swift-UVOT