Seti Observations of Exoplanets With the Allen Telescope Array

Abstract

We report radio SETI observations on a large number of known exoplanets and other nearby star systems using the Allen Telescope Array (ATA). Observations were made over about 19000 hours from May 2009 to Dec 2015. This search focused on narrow-band radio signals from a set totaling 9293 stars, including 2015 exoplanet stars and Kepler objects of interest and an additional 65 whose planets may be close to their Habitable Zone. The ATA observations were made using multiple synthesized beams and an anticoincidence filter to help identify terrestrial radio interference. Stars were observed over frequencies from 1-9 GHz in multiple bands that avoid strong terrestrial communication frequencies. Data were processed in near-real time for narrow-band (0.7-100 Hz) continuous and pulsed signals, with transmitter/receiver relative accelerations from -0.3 to 0.3 m/s 2 . A total of 1.9 x 10 8 unique signals requiring immediate follow-up were detected in observations covering more than 8 x 10 6 star-MHz. We detected no persistent signals from extraterrestrial technology exceeding our frequency-dependent sensitivity threshold of 180 -310 10 -26 W m -2 .

The Breakthrough Listen Search for Intelligent Life: 1.1–1.9 GHz Observations of 692 Nearby Stars

“…This suggests that by using these two results together we can put a joint constraint on a luminosity function of artificial transmitters. Harp et al (2016). j Distance to Kepler30, the maximum distance found for this group.…”

“…An obvious extension to this type of analysis would be to consider the entire distribution of stars within a radio telescope's primary beam, both near and far, when conducting an observation. Harp et al (2016). These values were used in the figure-of-merit calculations.…”

“…The potential spectral similarity between anthropogenic radio-frequency interference (RFI) and extraterrestrial technological transmissions brings additional complications. The sheer immensity of the parameter space that must be explored is a potential explanation to the absence of radio detections of extraterrestrial intelligence, despite numerous previous efforts (Verschuur 1973;Tarter et al 1980;Bowyer et al 1983Bowyer et al , 1995Horowitz et al 1986;Steffes & Deboer 1994;Mauersberger et al 1996;Backus 1998;Werthimer et al 2000;Korpela et al 2011;Siemion et al 2013;Harp et al 2016;Gray & Mooley 2017).…”

Choosing a Maximum Drift Rate in a SETI Search: Astrophysical Considerations

“…Any signal with precisely zero drift rate is not accelerating radially with respect to the receiver, and so is likely also on the Earth's surface. This drift rate based RFI rejection has been performed in SETI searches using the Allen Telescope Array as well as the Breakthrough Listen Project (Harp et al 2016;Sheikh et al 2019 in prep). SETI Table 2.…”

“…Sullivan et al (1978) considered the Doppler drift of signals leaving the Earth, while Cornet & Stride (2003) pointed out that correlating "anomalous microwave phenomena" observed with telescopes such as the ATA to known drift rates within the solar system could allow for localization of a signal to a particular body. Harp et al (2016) notes that orbital or rotational motion of a transmitter in an exoplanetary system can produce a drift rate, but does not quantify what upper limits on this motion might be. In this paper we will take a different approach from these previous studies by calculating maximum drift rates from physically allowable accelerations, informed by knowledge from the last decade of exoplanetary discoveries.…”