J/ApJ/869/66 Search for extraterrestrial intelligence with ATA (Harp+, 2018)
The application of autocorrelation SETI search techniques in an ATA survey.
Harp G.R., Ackermann R.F., Astorga A., Arbunich J., Barrios J.,
Hightower K., Meitzner S., Barott W.C., Nolan M.C., Messerschmitt D.G.,
Vakoch D.A., Shostak S., Tarter J.C.
<Astrophys. J., 869, 66-66 (2018)>
=2018ApJ...869...66H 2018ApJ...869...66H (SIMBAD/NED BibCode)
ADC_Keywords: Interferometry; Radio lines; Exoplanets; QSOs; BL Lac objects;
Pulsars; Masers; Supernova remnants; Solar system; Stars, O; Sun
Keywords: astrobiology; instrumentation: detectors
instrumentation: interferometers; methods: data analysis
planetary systems; quasars: emission lines
Abstract:
We report a novel radio autocorrelation search for extraterrestrial
intelligence. For selected frequencies across the terrestrial
microwave window (1-10GHz), observations were conducted at the Allen
Telescope Array to identify artificial non-sinusoidal periodic signals
with radio bandwidths greater than 4Hz, which are capable of carrying
substantial messages with symbol rates from 4 to 106Hz. Out of 243
observations, about half (101) were directed toward sources with known
continuum flux ≳1Jy over the sampled bandwidth (quasars, pulsars,
supernova remnants, and masers), based on the hypothesis that they
might harbor heretofore undiscovered natural or artificial repetitive,
phase or frequency modulation. The rest of the observations were
directed mostly toward exoplanet stars with no previously discovered
continuum flux. No signals attributable to extraterrestrial technology
were found in this study. We conclude that the maximum probability
that future observations like the ones described here will reveal
repetitively modulated emissions is less than 5% for continuum sources
and exoplanets alike. The paper concludes by describing a new approach
to expanding this survey to many more targets and much greater
sensitivity using archived data from interferometers all over the
world.
Description:
Suppose extraterrestrial intelligence (ETI) were to construct a
powerful transmitter sending information at a bit rate between 103
and 109Hz. These signals can be detectable by autocorrelating the
electric field amplitude and phase, otherwise known as a field
autocorrelation (FAC) detection. Here we present what we believe to be
the first radio search for ETI using FAC detection of complex signals.
The Allen Telescope Array (ATA) is a dual-polarization 42-element
interferometer located in Northern California, comprising 6.1m dishes
and dual-linear polarization feeds that can operate in four
simultaneous frequency bands centered anywhere between 1 and 10GHz.
The signals from many ATA antennas are delayed and summed in a beam
former (Barott et al. 2011RaSc...46.1016B 2011RaSc...46.1016B). Complex-valued (8-bit
real, 8-bit imaginary, hence η∼1) samples from the beam former are
collected at a rate of 8.73MS/s. An anti-aliasing bandpass filter
before the digitizers limits the effective bandwidth to 7MHz. The
phased-array beam diameter can be estimated as 0.1deg/f, where f is
the observation frequency in GHz. All of the source data are freely
available in an internet archive (SETIquest: http://wiki.setiquest.info/).
Data collections were made over approximately 14 months (between 2010
January and 2011 March) and a full listing of all targets and
observation frequencies is presented in Table 3.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table3.dat 91 242 List of observations for this study
--------------------------------------------------------------------------------
See also:
VIII/65 : 1.4GHz NRAO VLA Sky Survey (NVSS) (Condon+ 1998)
IX/29 : ROSAT All-Sky Survey Faint Source Catalog (Voges+ 2000)
VIII/87 : The Allen Telescope Array 20cm Survey (ATATS). I. (Croft+ 2010)
J/A+A/410/847 : Galactic emission at decimeter wavelengths (Platania+, 2003)
J/ApJ/710/L58 : Coronal type II radio bursts in 2002 (Lobzin+, 2010)
J/ApJS/211/24 : Rotation periods of Kepler MS stars (McQuillan+, 2014)
J/A+A/581/L5 : Mid-IR/radio correlation for Ghat galaxies (Garrett+, 2015)
J/AJ/152/181 : SETI observations of exoplanets with the ATA (Harp+, 2016)
J/MNRAS/465/1789 : SCUBA-2 Cosmology Legacy Survey (Geach+, 2017)
J/PASP/129/E4501 : Search for extraterrestrial intelligence (Isaacson+, 2017)
http://wiki.setiquest.info/ : SETIquest homepage
Byte-by-byte Description of file: table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 2 A2 --- Set Set (1)
4- 21 A18 --- ID Source identifier
23- 24 I2 h RAh ? Hour of right ascension (J2000)
26- 27 I2 min RAm ? Minute of right ascension (J2000)
29- 30 I2 s RAs ? Second of right ascension (J2000)
32 A1 --- DE- Sign of declination (J2000)
34- 35 I2 deg DEd ? Degree of declination (J2000)
37- 38 I2 arcmin DEm ? Arcminute of declination (J2000)
40- 41 I2 arcsec DEs ? Arcsecond of declination (J2000)
43- 61 A19 --- Type Object type of the source
63- 66 I4 MHz Freq [611/8200] Frequence of observation
68 A1 --- l_Flux [~<] Flag on flux (∼ = varies)
70- 79 F10.1 Jy Flux [0/1000000]? Flux at observed frequence
81- 91 A11 "Y/M/D" Date Date of observation
--------------------------------------------------------------------------------
Note (1): Set as follows:
Q = Quasars (59 occurrences)
B = Blazars (20 occurrences)
M = Supernova remnants and masers (10 occurrences)
R = Pulsars (20 occurrences)
S = Stars --including Kepler exoplanets, O stars (79 occurrences)
P = Special pointings (17 occurrences)
C1 = Confirmation observations (intentionally away from some particular
source; 13 occurrences)
C2 = Confirmation observations (surveying radio-frequency interference (RFI)
at ATA; 24 occurrences)
--------------------------------------------------------------------------------
History:
From electronic version of the journal
(End) Prepared by Coralie Fix [CDS] 04-Nov-2019