2019PASP..131c4502H

In recent papers, Borra in 2013 and 2017, and Borra & Trottier in 2016, those authors claimed that the discovery of ultrashort (10^–12 s) optical pulses originating from stars and galaxies may be sent by extraterrestrial intelligence. I show that these signals are not astrophysical or instrumental in nature, but that they originate due to the nonrandom spacings of spectral absorption lines. They can be shown to arise in their clearest form in synthetic solar spectra, as these do not suffer from noise.