Determining and using an exoplanet-derived maximum drift rate in radio technosignature searches

Nov 17, 2020 - 11:00 am to 12:00 pm
Sofia Sheikh (Pennsylvania State University) via zoom

A radio transmitter which is accelerating with a non-zero radial component with respect to a receiver will produce a signal that appears to change its frequency over time: a signal with a non-zero “drift rate”. In radio technosignature searches (looking for signs of artificial/technological radio emission beyond Earth) the magnitude of the expected drift rate is unknown a priori, with the exception of the component from the Earth’s own radial acceleration. Therefore we must search a range of potential drift rates up to some maximum via balancing expected accelerations with computational constraints.

This talk will have two parts. First, I examine physical considerations, derived primarily from exoplanets, that constrain the maximum drift rate. I will explain why a normalized drift rate of 200 nHz (eg. 200 Hz/s at 1 GHz) is a physically-motivated guideline for this maximum. Second, I will discuss a novel radio technosignature search that was performed by the inaugural Penn State SETI Graduate Course in 2018: observing exoplanets during mid-transit to look for narrowband drifting signals. I will talk about the current status of the project, and how we are incorporating the new maximum drift rate found above.