A 1.1 to 1.9 GHz SETI Survey of the Kepler Field: I. A Search for Narrow-band Emission from Select Targets (1302.0845v1)

Abstract: We present a targeted search for narrow-band (< 5 Hz) drifting sinusoidal radio emission from 86 stars in the Kepler field hosting confirmed or candidate exoplanets. Radio emission less than 5 Hz in spectral extent is currently known to only arise from artificial sources. The stars searched were chosen based on the properties of their putative exoplanets, including stars hosting candidates with 380 K > T_eq > 230 K, stars with 5 or more detected candidates or stars with a super-Earth (R_p < 3 R_earth) in a > 50 day orbit. Baseband voltage data across the entire band between 1.1 and 1.9 GHz were recorded at the Robert C. Byrd Green Bank Telescope between Feb--Apr 2011 and subsequently searched offline. No signals of extraterrestrial origin were found. We estimate that fewer than ~1% of transiting exoplanet systems host technological civilizations that are radio loud in narrow-band emission between 1-2 GHz at an equivalent isotropically radiated power (EIRP) of ~1.5 x 10^21 erg s^-1, approximately eight times the peak EIRP of the Arecibo Planetary Radar, and we limit the the number of 1-2 GHz narrow-band-radio-loud Kardashev type II civilizations in the Milky Way to be < 10^-6 M_solar^-1. Here we describe our observations, data reduction procedures and results.

Overview of a SETI Survey of the Kepler Field

The paper presents a targeted Search for Extraterrestrial Intelligence (SETI) survey, meticulously analyzing narrow-band drifting sinusoidal radio emissions from 86 stars within the Kepler field known to host either confirmed or candidate exoplanets. This survey focuses on a frequency band between 1.1 and 1.9 GHz utilizing the Robert C. Byrd Green Bank Telescope. This paper was driven by the understanding that artificial sources are currently the sole emitters of radio signals narrower than 5 Hz in the spectral region, hence narrowing the search down to possible technological origin sources.

Methodology

• Target Selection: The targets were selected based on certain exoplanetary properties, including but not limited to equilibrium temperature constraints, presence of five or more exoplanet candidates, or super-Earths in extended orbits. This methodological choice allows for optimizing detection of potential signals from advanced technological civilizations.
• Detection Mechanism: SETI observations utilized the Green Bank Ultimate Pulsar Processor digital backend in a "baseband recording" mode to capture the full band of 800 MHz for offline analysis. The observational strategy involved alternating 'on-source' and 'off-source' pointings to distinguish potential extraterrestrial signals from terrestrial interference.

Results

The analysis identified no signals that could be attributed to extraterrestrial origin. The research concludes that fewer than 1% of transiting exoplanet systems might host civilizations that are radio loud in narrow-band emissions within the survey frequency range and an EIRP comparable to or greater than eight times Arecibo’s peak radar power.

Discussion and Implications

Despite the lack of detection, the implications are significant. The data offer stringent limits on the presence of radio-loud advanced civilizations within the surveyed region, suggesting that Kardashev Type II civilizations detectable at radio frequencies may be exceedingly rare in the Milky Way. From a methodological standpoint, this work highlights the effectiveness of cadence-based observation techniques in mitigating interference and provides a measure of range and sensitivity relative to terrestrial technologies such as the Arecibo Planetary Radar. It projects further SETI endeavors into the utilization of upcoming technological advancements and more sensitive instruments like the Square Kilometer Array.

Future Directions

The paper notes that technological advancements, especially in semiconductor technologies, will enable more exhaustive exploration of the electromagnetic spectrum. This future capability will facilitate comprehensive surveys across broader frequencies and target classes, enhancing the potential of detecting extraterrestrial life forms or their technological signatures. Therefore, the continuation of such rigorous scientific astronomical inquiries, augmented by future innovations, holds promise in increasing the likelihood of identifying signals from extraterrestrial intelligent life.