109 research outputs found
All-sky Radio SETI
Over the last decade, Aperture Arrays (AA) have successfully replaced
parabolic dishes as the technology of choice at low radio frequencies - good
examples are the MWA, LWA and LOFAR. Aperture Array based telescopes present
several advantages, including sensitivity to the sky over a very wide
field-of-view. As digital and data processing systems continue to advance, an
all-sky capability is set to emerge, even at GHz frequencies. We argue that
assuming SETI events are both rare and transitory in nature, an instrument with
a large field-of-view, operating around the so-called water-hole (1-2 GHz),
might offer several advantages over contemporary searches. Sir Arthur C. Clarke
was the first to recognise the potential importance of an all-sky radio SETI
capability, as presented in his book, Imperial Earth. As part of the global SKA
(Square Kilometre Array) project, a Mid-Frequency Aperture Array (MFAA)
prototype known as MANTIS (Mid- Frequency Aperture Array Transient and
Intensity-Mapping System) is now being considered as a precursor for SKA-2.
MANTIS can be seen as a first step towards an all-sky radio SETI capability at
GHz frequencies. This development has the potential to transform the field of
SETI research, in addition to several other scientific programmes.Comment: 7 pages, 4 figures, accepted for publication, Proceedings of Science,
workshop on "MeerKAT Science: On the Pathway to the SKA", held in
Stellenbosch 25-27 May 2016. Comments welcom
Fast Radio Burst 121102 Pulse Detection and Periodicity: A Machine Learning Approach
We report the detection of 72 new pulses from the repeating fast radio burst
FRB 121102 in Breakthrough Listen C-band (4-8 GHz) observations at the Green
Bank Telescope. The new pulses were found with a convolutional neural network
in data taken on August 26, 2017, where 21 bursts have been previously
detected. Our technique combines neural network detection with dedispersion
verification. For the current application we demonstrate its advantage over a
traditional brute-force dedis- persion algorithm in terms of higher
sensitivity, lower false positive rates, and faster computational speed.
Together with the 21 previously reported pulses, this observa- tion marks the
highest number of FRB 121102 pulses from a single observation, total- ing 93
pulses in five hours, including 45 pulses within the first 30 minutes. The
number of data points reveal trends in pulse fluence, pulse detection rate, and
pulse frequency structure. We introduce a new periodicity search technique,
based on the Rayleigh test, to analyze the time of arrivals, with which we
exclude with 99% confidence pe- riodicity in time of arrivals with periods
larger than 5.1 times the model-dependent time-stamp uncertainty. In
particular, we rule out constant periods >10 ms in the barycentric arrival
times, though intrinsic periodicity in the time of emission remains plausible.Comment: 32 pages, 10 figure
Background Contamination of the Project Hephaistos Dyson Spheres Candidates
Project Hephaistos recently identified seven M-dwarfs as possible Dyson Spheres (DS) candidates. We have cross-matched three of these candidates (A, B and G) with radio sources detected in various all-sky surveys. The radio sources are offset from the Gaia stellar positions by ∼4.9, ∼0.4 and ∼5.″0 for candidates A, B, and G respectively. We propose that Dust obscured galaxies (DOGs) lying close to the line-of-sight of these M-dwarf stars significantly contribute to the measured WISE mid-IR flux densities in the WISE W3 and W4 wave bands. These three stars have therefore been misidentified as DS candidates. We also note that with an areal sky density of 9 × 10−6 per square arcsecond, Hot DOGs can probably account for the contamination of all 7 DS candidates drawn from an original sample of 5 million stars
A Deep Neural Network Based Reverse Radio Spectrogram Search Algorithm
Modern radio astronomy instruments generate vast amounts of data, and the
increasingly challenging radio frequency interference (RFI) environment
necessitates ever-more sophisticated RFI rejection algorithms. The "needle in a
haystack" nature of searches for transients and technosignatures requires us to
develop methods that can determine whether a signal of interest has unique
properties, or is a part of some larger set of pernicious RFI. In the past,
this vetting has required onerous manual inspection of very large numbers of
signals. In this paper we present a fast and modular deep learning algorithm to
search for lookalike signals of interest in radio spectrogram data. First, we
trained a B-Variational Autoencoder on signals returned by an energy detection
algorithm. We then adapted a positional embedding layer from classical
Transformer architecture to a embed additional metadata, which we demonstrate
using a frequency-based embedding. Next we used the encoder component of the
B-Variational Autoencoder to extract features from small (~ 715,Hz, with a
resolution of 2.79Hz per frequency bin) windows in the radio spectrogram. We
used our algorithm to conduct a search for a given query (encoded signal of
interest) on a set of signals (encoded features of searched items) to produce
the top candidates with similar features. We successfully demonstrate that the
algorithm retrieves signals with similar appearance, given only the original
radio spectrogram data. This algorithm can be used to improve the efficiency of
vetting signals of interest in technosignature searches, but could also be
applied to a wider variety of searches for "lookalike" signals in large
astronomical datasets.Comment: 8 pages, 8 figure
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