Far Ultraviolet Radiation Environments of FGKM Dwarfs
Fernando Cruz Aguirre; University of Colorado Boulder
Far ultraviolet (FUV; 912 – 1700 Å) spectroscopic observations of F, G, K, and M dwarf stars allow for the study of several chromospheric and transition region emission features, which drive photochemistry in the atmospheres of exoplanets. Atmospheric composition models and proper interpretation of observed spectral features depend heavily on accurate stellar inputs. An observational challenge with stellar H I Lyα (1216 Å) and O I triplet (1302, 1305, and 1306 Å) emission comes from geocoronal emission, or airglow, from the Earth’s exosphere. The orbit of the Hubble Space Telescope (HST) lies within the exosphere, making all observations with the Cosmic Origins Spectrograph (COS) contaminated by airglow. A subtraction method was developed using archival airglow observations, and a community tool has been created to perform the airglow subtractions. Using this tool, ~100 Lyα and O I triplet profiles of FGKM dwarfs were recovered, and several power law relationships were developed for predicting Lyα and O I emission. In addition to HST/COS observations, dedicated sounding rocket missions also allow for capturing the FUV radiation environment of dwarf stars. The SISTINE-2 sounding rocket payload observed Procyon A (F5 IV-V), simultaneously capturing several key emission features across a broad FUV bandpass (1010 – 1565 Å). Flight data is combined with archival data and stellar models to develop the first full panchromatic spectrum of a mid-F type star. This spectrum, along with power laws for predicting Lyα and O I triplet emission, are now available to model and interpret interactions between host stars and their planets.
Fernando Cruz Aguirre is a doctoral candidate at the University of Colorado, Boulder. He is part of the Colorado Ultraviolet Spectroscopy Program, a group of scientists and engineers who develop UV instruments and technologies. Fernando was the lead graduate student on the second flight of the SISTINE sounding rocket, which was designed to investigate the FUV radiation environments around main sequence dwarf stars. In addition to his instrumentation experience, Fernando also led a large archival HST program focused on recovering airglow contaminated FUV spectra of FGKM dwarf stars. Currently, Fernando is expanding his mission development skills as part of the inaugural session of the Astrophysics Mission Design School.