Exoplanet Atmospheres

The chemical composition and loss of mass from an exoplanet's atmosphere depends on the ultraviolet, extreme-ultraviolet, and X-radiation from the host star and the interaction between the stellar wind and gas in the planet's exosphere. The photochemistry of such important molecules as water, oxygen, ozone, methane, and carbon dioxide in the atmospheres of exoplanets depends critically on the UV and extreme-UV radiation of their host stars. We have observed the UV radiation of K and M dwarf host stars for which the Lyman-alpha radiation dominates the UV spectrum but is largely absorbed by the interstellar medium. We show how to reconstruct the intrinsic Lyman-alpha flux and infer the unobservable extreme-UV radiation of host stars. The these data show the quantitative effects of UV and Lyman-alpha radiation on the chemistry of exoplanets.

Research Objectives:

Observe and place in the HST archives very high quality UV spectra of K and M dwarfs host stars of known exoplanets.
Reconstruct the intrinsic Lyman-alpha line profiles and fluxes of exoplanet host stars.
Estimate the extreme-UV radiation of exoplanet host stars.
Compute photochemistry models of exoplanets of M dwarf host stars with measured UV fluxes, reconstructed Lyman-alpha fluxes, and estimated extreme-UV fluxes.
Develop scaling laws that relate different flux regions of exoplanet host stars.

Important Results and Discoveries:

Obtained ultraviolet spectra of stars with exoplanets as a part of major observing programs (e.g., MUSCLES and Mega-MUSCLES) with HST.
Provided empirical results concerning the effect of Lyman-alpha emission on the chemical composition of exoplanet atmospheres.
Developed a technique for estimating the unobservable extreme ultraviolet emission of stars that drives the mass-loss rates from exoplanet atmospheres.
Wrote the book "Host Stars and their Effects on Exoplanet Atmospheres" as a guide to exoplanet atmosphere modelers concerning the stellar radiation and phenomena that should take into account.

Papers published in refereed journals since 2000:

Wood, B.E., Muller, H.R., Redfield, S., Linsky, J.L., et al.: 2021, "New Observational Constraints on the Winds of M dwarf Stars", Asatrophysical Journal, 915, 37
Carleo, I., Youngblood, A., Redfield, S., Linsky, J.L., et al.: 2021, "A multiwavelength look at the GJ 9827b system: No evidence of extended atmospheres in GJ 9828b and d from HST and CARMENES data", Astronomical Journal, 161, 136C
Melbourne, K., Youngblood, A., France, K., Linsky, J.L., et al.: 2020 "Estimating the ultraviolet emission of M dwarfs with exoplanets from Ca II and Halpha", Astronomical Journal, 160, 269M
Miguel, Y., Kaltenegger, L., Linsky, J.L., and Rugheimer, S.: 2015, "The effect of Lyman-alpha radiation on mini-Neptune atmospheres around M stars: application to GJ 436b", Monthly Notices of the Royal Astronomical Society, 446, 345
Rugheimer, S., Kaltenegger, L., Segura, A., Linsky, J., and Mohanty, S.: 2015, "Effect of UV radiation on the spectral fingerprints of Earth-like planets orbiting M dwarfs", Astrophysical Journal, 809, 57
Cowan, N.B., Green, T., Angerhausen, D., Linsky, J.L., et al.: 2015, "Characterizing transiting planet atmospheres through 2025", Publ. Astronomical Society Pacific, 127, 311
Linsky, J.L.: 2014, "The radiation environment of exoplanet atmospheres", Challenges, 5, 351
Kulow, J.R., France, K., Linsky, J.L., and Parke Loyd, R.O.: 2014, "Lyman alpha spectroscopy and the neutral hydrogen tail of the hot Neptune GJ 436b", Astrophysical Journal, 786, 132
France, K., Linsky, J.L., and Parke Loyd, R.O.: 2014, "The ultraviolet radiation environment in the habitable zones around low-mass exoplanet host stars", Astrophysics and Space Science, 354, 3
Tian, F., France, K., Linsky, J.L. et al.: 2014, "High stellar FUV/NUV ration and oxygen contents in the atmospheres of potentially habitable planets", Earth and Planetary Science Letters, 385, 22
Lammer, H., Blanc, M., Linsky, J.L. et al.: 2013, "The science of exoplanets and their systems", Astrobiology, 13, 9
France, K., Froning, C.S., Linsky, J.L. et al.: 2013, "The ultraviolet radiation environment around M dwarf exoplanet host stars", Astrophysical Journal, 763, 149
Linsky, J.L., Yang, H., France, K. et al.: 2010, "Observations of mass loss from the transiting exoplanet HD 209458b", Astrophysical Journal, 717, 1291
France, K., Stocke, J.T., Yang, H., Linsky, J.L. et al.: 2010, "Searching for far-ultraviolet auroral/dayglow emission from HD209458b", Astrophysical Journal, 712, 1277
Gomez de Castro, A.I., Lecavelier, A., d'Avillez, M., Linsky, J.L., and Cernicharo, J.: 2006, "The formation of planetary systems from the ISM to planets", Astrophysics and Space Science, 303, 33

Review papers and conference papers since 2000:

Herbst, K., Baalmann, L.R., Bykov, A., Linsky, J.L., et al.: 2022, "Astrospheres of planet-hosting cool stars and beyond: when modeling meets observations", Space Science Reviews, 218, 29H

Linsky, J.L.: 2019, "Host Stars and their Effects on Exoplanet Atmospheres", book published by Springer

Linsky, J.L. and Guedel, M.: 2015, "Exoplanet host star radiation and plasma environment", in Characterizing Stellar and Exoplanetary Environments ed. H. Lammer and M. Khodachenko, Astrophysics and Space Science Library 411, 3

Fossati, L., Haswell, C.A., Linsky, J.L. and Kislyakova, K. G.: 2015, "Observations of exoplanet atmospheres and surrounding environments", in Characterizing Stellar and Exoplanetary Environments ed. H. Lammer and M. Khodachenko, Astrophysics and Space Science Library 411, 59

Linsky, J.L., France, K., and Ayres, T.R.:2015, "Predicting the extreme-UV and Lyman-alpha fluxes received by exoplanets from their host stars",in 18th Cambridge Workshop on Cool Stars, Stellar Systems, and the Sun, ed. G. van Belle and H.C. Harris, p. 831

Linsky, J.L., France, K., and Ayres, T.: 2014, "Reconstructing the stellar UV and EUV emission that controls the chemistry of exoplanet atmospheres" in Formation, Detection, and Characterization of Extrasolar Habitable Planets, Proc. IAU Symposium No. 293 Return to main page