Model of the Search For Extraterrestrial Intelligence with Coronagraphic Imaging

We present modeled detection limits of the Gemini Planet Imager (GPI) and the Wide-Field Infrared Space Telescope (WFIRST) to an optical and infrared laser which could be used by an extraterrestrial civilization to signal their presence. GPI and WFIRST could utilize a coronagraph to search for extraterrestrial intelligence (SETI) in the present and future. We use archival data for GPI stars and simulated WFIRST observations to find the detectable flux ratio of a laser signal to residual scattered starlight around the target star. This flux ratio is then converted to detectable power as a function of distance from the parent star. For GPI, we assume a monochromatic laser wavelength of 1.55 $μ$m, and a wavelength of 575 nm for WFIRST. We assume the lasers are projected through a 10-m aperture, and that the intensity of the laser beam follows a Gaussian profile. Our analysis is performed on 6 stars with spectral types later than F within 20 pc (with an emphasis on solar analogs at different distances). The most notable result is the detection limit for $τ$ Ceti, a G5V star with four known exoplanets, two of those within the habitable zone (HZ). The result shows that a 24 kW laser is detectable from $τ$ Ceti from outside of the HZ with GPI and a 7.3 W laser is detectable from within $τ$ Ceti's HZ by WFIRST.

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