114 research outputs found
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
Gravity Spy: Integrating Advanced LIGO Detector Characterization, Machine Learning, and Citizen Science
(abridged for arXiv) With the first direct detection of gravitational waves,
the Advanced Laser Interferometer Gravitational-wave Observatory (LIGO) has
initiated a new field of astronomy by providing an alternate means of sensing
the universe. The extreme sensitivity required to make such detections is
achieved through exquisite isolation of all sensitive components of LIGO from
non-gravitational-wave disturbances. Nonetheless, LIGO is still susceptible to
a variety of instrumental and environmental sources of noise that contaminate
the data. Of particular concern are noise features known as glitches, which are
transient and non-Gaussian in their nature, and occur at a high enough rate so
that accidental coincidence between the two LIGO detectors is non-negligible.
In this paper we describe an innovative project that combines crowdsourcing
with machine learning to aid in the challenging task of categorizing all of the
glitches recorded by the LIGO detectors. Through the Zooniverse platform, we
engage and recruit volunteers from the public to categorize images of glitches
into pre-identified morphological classes and to discover new classes that
appear as the detectors evolve. In addition, machine learning algorithms are
used to categorize images after being trained on human-classified examples of
the morphological classes. Leveraging the strengths of both classification
methods, we create a combined method with the aim of improving the efficiency
and accuracy of each individual classifier. The resulting classification and
characterization should help LIGO scientists to identify causes of glitches and
subsequently eliminate them from the data or the detector entirely, thereby
improving the rate and accuracy of gravitational-wave observations. We
demonstrate these methods using a small subset of data from LIGO's first
observing run.Comment: 27 pages, 8 figures, 1 tabl
Planet Hunters: The First Two Planet Candidates Identified by the Public using the Kepler Public Archive Data
Planet Hunters is a new citizen science project, designed to engage the
public in an exoplanet search using NASA Kepler public release data. In the
first month after launch, users identified two new planet candidates which
survived our checks for false- positives. The follow-up effort included
analysis of Keck HIRES spectra of the host stars, analysis of pixel centroid
offsets in the Kepler data and adaptive optics imaging at Keck using NIRC2.
Spectral synthesis modeling coupled with stellar evolutionary models yields a
stellar density distribution, which is used to model the transit orbit. The
orbital periods of the planet candidates are 9.8844 \pm0.0087 days (KIC
10905746) and 49.7696 \pm0.00039 (KIC 6185331) days and the modeled planet
radii are 2.65 and 8.05 R\oplus. The involvement of citizen scientists as part
of Planet Hunters is therefore shown to be a valuable and reliable tool in
exoplanet detection.Comment: Submitted to MNRAS, added 1 line to table
Planetary Candidates Observed by Kepler, III: Analysis of the First 16 Months of Data
New transiting planet candidates are identified in sixteen months (May 2009 -
September 2010) of data from the Kepler spacecraft. Nearly five thousand
periodic transit-like signals are vetted against astrophysical and instrumental
false positives yielding 1,091 viable new planet candidates, bringing the total
count up to over 2,300. Improved vetting metrics are employed, contributing to
higher catalog reliability. Most notable is the noise-weighted robust averaging
of multi-quarter photo-center offsets derived from difference image analysis
which identifies likely background eclipsing binaries. Twenty-two months of
photometry are used for the purpose of characterizing each of the new
candidates. Ephemerides (transit epoch, T_0, and orbital period, P) are
tabulated as well as the products of light curve modeling: reduced radius
(Rp/R*), reduced semi-major axis (d/R*), and impact parameter (b). The largest
fractional increases are seen for the smallest planet candidates (197% for
candidates smaller than 2Re compared to 52% for candidates larger than 2Re) and
those at longer orbital periods (123% for candidates outside of 50-day orbits
versus 85% for candidates inside of 50-day orbits). The gains are larger than
expected from increasing the observing window from thirteen months (Quarter 1--
Quarter 5) to sixteen months (Quarter 1 -- Quarter 6). This demonstrates the
benefit of continued development of pipeline analysis software. The fraction of
all host stars with multiple candidates has grown from 17% to 20%, and the
paucity of short-period giant planets in multiple systems is still evident. The
progression toward smaller planets at longer orbital periods with each new
catalog release suggests that Earth-size planets in the Habitable Zone are
forthcoming if, indeed, such planets are abundant.Comment: Submitted to ApJS. Machine-readable tables are available at
http://kepler.nasa.gov, http://archive.stsci.edu/kepler/results.html, and the
NASA Exoplanet Archiv
K2-288Bb: A Small Temperate Planet in a Low-mass Binary System Discovered by Citizen Scientists
Original content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.Observations from the Kepler and K2 missions have provided the astronomical community with unprecedented amounts of data to search for transiting exoplanets and other astrophysical phenomena. Here, we present K2-288, a low-mass binary system (M2.0 ± 1.0; M3.0 ± 1.0) hosting a small (R p = 1.9 R â), temperate (T eq = 226 K) planet observed in K2 Campaign 4. The candidate was first identified by citizen scientists using Exoplanet Explorers hosted on the Zooniverse platform. Follow-up observations and detailed analyses validate the planet and indicate that it likely orbits the secondary star on a 31.39-day period. This orbit places K2-288Bb in or near the habitable zone of its low-mass host star. K2-288Bb resides in a system with a unique architecture, as it orbits at >0.1 au from one component in a moderate separation binary (a proj ~ 55 au), and further follow-up may provide insight into its formation and evolution. Additionally, its estimated size straddles the observed gap in the planet radius distribution. Planets of this size occur less frequently and may be in a transient phase of radius evolution. K2-288 is the third transiting planet system identified by the Exoplanet Explorers program and its discovery exemplifies the value of citizen science in the era of Kepler, K2, and the Transiting Exoplanet Survey Satellite
LSST: from Science Drivers to Reference Design and Anticipated Data Products
(Abridged) We describe here the most ambitious survey currently planned in
the optical, the Large Synoptic Survey Telescope (LSST). A vast array of
science will be enabled by a single wide-deep-fast sky survey, and LSST will
have unique survey capability in the faint time domain. The LSST design is
driven by four main science themes: probing dark energy and dark matter, taking
an inventory of the Solar System, exploring the transient optical sky, and
mapping the Milky Way. LSST will be a wide-field ground-based system sited at
Cerro Pach\'{o}n in northern Chile. The telescope will have an 8.4 m (6.5 m
effective) primary mirror, a 9.6 deg field of view, and a 3.2 Gigapixel
camera. The standard observing sequence will consist of pairs of 15-second
exposures in a given field, with two such visits in each pointing in a given
night. With these repeats, the LSST system is capable of imaging about 10,000
square degrees of sky in a single filter in three nights. The typical 5
point-source depth in a single visit in will be (AB). The
project is in the construction phase and will begin regular survey operations
by 2022. The survey area will be contained within 30,000 deg with
, and will be imaged multiple times in six bands, ,
covering the wavelength range 320--1050 nm. About 90\% of the observing time
will be devoted to a deep-wide-fast survey mode which will uniformly observe a
18,000 deg region about 800 times (summed over all six bands) during the
anticipated 10 years of operations, and yield a coadded map to . The
remaining 10\% of the observing time will be allocated to projects such as a
Very Deep and Fast time domain survey. The goal is to make LSST data products,
including a relational database of about 32 trillion observations of 40 billion
objects, available to the public and scientists around the world.Comment: 57 pages, 32 color figures, version with high-resolution figures
available from https://www.lsst.org/overvie
Galaxy Formation Theory
We review the current theory of how galaxies form within the cosmological
framework provided by the cold dark matter paradigm for structure formation.
Beginning with the pre-galactic evolution of baryonic material we describe the
analytical and numerical understanding of how baryons condense into galaxies,
what determines the structure of those galaxies and how internal and external
processes (including star formation, merging, active galactic nuclei etc.)
determine their gross properties and evolution. Throughout, we highlight
successes and failings of current galaxy formation theory. We include a review
of computational implementations of galaxy formation theory and assess their
ability to provide reliable modelling of this complex phenomenon. We finish
with a discussion of several "hot topics" in contemporary galaxy formation
theory and assess future directions for this field.Comment: 58 pages, to appear in Physics Reports. This version includes minor
corrections and a handful of additional reference
Planet Hunters TESS. V. A Planetary System Around a Binary Star, Including a Mini-Neptune in the Habitable Zone
We report on the discovery and validation of a transiting long-period mini-Neptune orbiting a bright (V = 9.0 mag) G dwarf (TOI 4633; R = 1.05 R â, M = 1.10 M â). The planet was identified in data from the Transiting Exoplanet Survey Satellite by citizen scientists taking part in the Planet Hunters TESS project. Modelling of the transit events yields an orbital period of 271.9445 ± 0.0040 days and radius of 3.2 ± 0.20 R â. The Earth-like orbital period and an incident flux of 1.56â0.16+0.20 F â places it in the optimistic habitable zone around the star. Doppler spectroscopy of the system allowed us to place an upper mass limit on the transiting planet and revealed a non-transiting planet candidate in the system with a period of 34.15 ± 0.15 days. Furthermore, the combination of archival data dating back to 1905 with new high angular resolution imaging revealed a stellar companion orbiting the primary star with an orbital period of around 230 yr and an eccentricity of about 0.9. The long period of the transiting planet, combined with the high eccentricity and close approach of the companion star makes this a valuable system for testing the formation and stability of planets in binary systems
The K2-138 system:a near-resonant chain of five sub-neptune planets discovered by citizen scientists
K2-138 is a moderately bright (V = 12.2, K = 10.3) main-sequence K star observed in Campaign 12 of the NASA K2 mission. It hosts five small (1.6â3.3 ) transiting planets in a compact architecture. The periods of the five planets are 2.35, 3.56, 5.40, 8.26, and 12.76 days, forming an unbroken chain of near 3:2 resonances. Although we do not detect the predicted 2â5 minute transit timing variations (TTVs) with the K2 timing precision, they may be observable by higher-cadence observations with, for example, Spitzer or CHEOPS. The planets are amenable to mass measurement by precision radial velocity measurements, and therefore K2-138 could represent a new benchmark system for comparing radial velocity and TTV masses. K2-138 is the first exoplanet discovery by citizen scientists participating in the Exoplanet Explorers project on the Zooniverse platform
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