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2022 ◽  
Author(s):  
Peter Ma ◽  
Cherry Ng ◽  
Leandro Rizk ◽  
Steve Croft ◽  
Andrew Siemion ◽  
...  

Abstract The goal of the Search for Extraterrestrial Intelligence (SETI) is to quantify the prevalence of technological life beyond Earth via their “technosignatures". One theorized technosignature are narrowband Doppler drifting radio signals. The principal challenge in conducting SETI in the radio domain is developing a generalized technique to reject human radio frequency interference (RFI) that dominate the features across the band in searches for technosignatures. Here, we present the first comprehensive deep-learning based technosignature search to date, returning 8 promising ETI signals-of-interest for re-observation as part of the Breakthrough Listen initiative. The search comprises 820 unique targets observed with the Robert C. Byrd Green Bank Telescope, totaling over 480 hr of on-sky data. We implement a novel β−Convolutional Variational Autoencoder with an embedded discriminator combined with Random Forest Decision Trees to classify technosignature candidates in a semiunsupervised manner. We compare our results with prior classical techniques on the same dataset and conclude that our algorithm returns more convincing and novel signals-of-interest with a manageable false positive rate. This new approach presents itself as a leading solution in accelerating SETI and other transient research into the age of data-driven astronomy.


2021 ◽  
Vol 21 (11) ◽  
pp. 276
Author(s):  
Somaye Soomandar ◽  
Abbas Abedi

Abstract We investigate a short-period W UMa binary KIC 9026766 with an orbital period of 0.2721278d in the Kepler field of view. By applying an automated q-search for the folded light curve and producing a synthetic light curve for this object based on the PHOEBE code, we calculate the fundamental stellar parameters. We also analyze the O − C curve of the primary minima. The orbital period changes can be attributed to the combination of an upward quadratic function and light-travel time effect (LTTE) due to a possible third body with a minimum mass of 0.029 M ⊙ and an orbital period of 972.5866 ±0.0041d. The relative luminosity of the primary and secondary eclipses (Min I − Min II) is calculated. The periodogram of the residuals of the LTTE and Min I − Min II show peaks with the same period of 0.8566d. The background effect of two nearby stars on our target is the possible reason for this signal. By considering the amplitudes and periods of the remaining signals in the O − C curve of minima, spot motion is possible.


2021 ◽  
Vol 922 (2) ◽  
pp. 105
Author(s):  
Yong Yang ◽  
Jingkun Zhao ◽  
Jiajun Zhang ◽  
Xianhao Ye ◽  
Gang Zhao

Abstract We revisit the moving groups (MGs) in the solar neighborhood with a sample of 91,969 nearby stars constructed from LAMOST DR7. Using the wavelet technique and Monte Carlo simulations, five MGs together with a new candidate located at V≃−130 km s−1 are detected simultaneously in V − U 2 + 2 V 2 space. Taking into account the other known MGs, we conclude that MGs in the Galactic disk are spaced by approximately 15–25 km s−1 along V velocity. The origin of detected MGs is analyzed through the distributions of [Fe/H]−[Mg/Fe] and ages. Our results support attributing the origin to the continuous resonant mechanisms probably induced by the bar or spiral arms of the Milky Way.


2021 ◽  
Vol 162 (6) ◽  
pp. 252
Author(s):  
Stephen Kerby ◽  
Jason T. Wright

Abstract Several recent works have proposed a “stellar relay” transmission system in which a spacecraft at the focus of a star’s gravitational lens achieves dramatic boosts in the gain of an outgoing or incoming interstellar transmission. We examine some of the engineering requirements of a stellar relay system, evaluate the long-term sustainability of a gravitational relay, and describe the perturbations and drifts that must be actively countered to maintain a relay-star-target alignment. The major perturbations on a relay-Sun-target alignment are the inwards gravity of the Sun and the reflex motion of the Sun imparted by the planets. These ∼m s−1 yr−1 accelerations can be countered with modern propulsion systems over century-long timescales. This examination is also relevant for telescope designs aiming to use the Sun as a focusing element. We additionally examine prospects for an artifact SETI search to observe stellar relays placed around the Sun by an extraterrestrial intelligence and suggest certain nearby stars that are relatively unperturbed by planetary systems as favorable nodes for a stellar relay communications system.


Author(s):  
J. A. Moore ◽  
B. Gendre ◽  
D. M. Coward ◽  
H. Crisp ◽  
A. Klotz

The 1.0 metre f/4 fast-slew Zadko Telescope was installed in June 2008 approximately seventy kilometres north of Perth at Yeal, in the Shire of Gingin, Western Australia. Since the Zadko Telescope has been in operation it has proven its worth by detecting numerous Gamma Ray Burst afterglows, two of these being the most distant 'optical transients' imaged by an Australian telescope. Other projects include a contract with the European Space Agency (ESA) to image potentially hazardous near Earth asteroids (2019), monitoring space weather on nearby stars (2019), and photometry of a transit of Saturn's moon Titan (2018). Another active Zadko Telescope project is tracking Geostationary satellites and attempting to use photometry to classify various space debris (defunct satellites). The Zadko Telescope's importance as a potential tool for education, training, and public outreach cannot be underestimated, as the global awareness of the importance of astronomy (and space science) as a context for teaching science continues to increase. An example of this was the national media coverage of its contribution to the discovery of colliding neutron stars in 2017, capturing the imagination of the public. In this proceeding, I will focus on the practical aspects of managing a robotic Observatory, focusing on the sustainability of the Observatory and the technical management involved in hosting different commercial projects. I will review the evolution of the Observatory, from its early, single instrument, state to its current multi-telescope and multi-instrument capabilities. I will finish by outlining the future of the Observatory and the site.


Author(s):  
Kevin Wagner ◽  
Steve Ertel ◽  
Jordan Stone ◽  
Jarron Leisenring ◽  
Dániel Apai ◽  
...  

2021 ◽  
Author(s):  
Rory Bowens ◽  
Michael Meyer ◽  
Christian Delacroix ◽  
Olivier Absil ◽  
Roy van Boekel ◽  
...  

<p>Direct imaging is a powerful exoplanet discovery technique that is complimentary to other techniques with great promise in the era of 30-meter class telescopes. Space-based transit surveys have revolutionized our understanding of the frequency of planets at small orbital radii around sun-like stars. The next generation of extremely large ground-based telescopes will have the angular resolution and sensitivity to directly image planets with R < 4 Earth radii around the very nearest stars. Here we predict yields from a direct imaging survey of a volume-limited sample of sun-like stars with the Mid-Infrared ELT Imager and Spectrograph (METIS) instrument, planned for the 39-m European Southern Observatory (ESO) Extremely Large Telescope (ELT) that is expected to be operational towards the end of the decade. Using Kepler occurrence rates, a sample of stars with spectral types A-K within 6.5 pc, and simulated contrast curves based on an advanced model of what is achievable from coronagraphic imaging with adaptive optics, we estimate the expected yield from METIS using Monte Carlo simulations. We find the METIS expected yield of small planets in the N2 band (10.10 - 12.40 μm) is 1.15 planets which is greater than similar observations in the L (3.70 - 3.95 μm) and M (4.70 - 4.90 μm) bands. We also determine a 42% chance of detecting at least one Jovian planet in the background limited regime assuming a 1-hour integration. We calculate the yield per star and estimate optimal observing revisit times to increase the yield. We also analyze this survey if performed in the northern hemisphere and find there are additional targets worth considering. Finally, we present an observing strategy in order to maximize the possible yield for limited telescope time, resulting in 1.52 expected planets in the N2 band.</p>


Author(s):  
John H D Harrison ◽  
Amy Bonsor ◽  
Mihkel Kama ◽  
Andrew M Buchan ◽  
Simon Blouin ◽  
...  

Abstract White dwarfs that have accreted planetary bodies are a powerful probe of the bulk composition of exoplanetary material. In this paper, we present a Bayesian model to explain the abundances observed in the atmospheres of 202 DZ white dwarfs by considering the heating, geochemical differentiation, and collisional processes experienced by the planetary bodies accreted, as well as gravitational sinking. The majority (>60%) of systems are consistent with the accretion of primitive material. We attribute the small spread in refractory abundances observed to a similar spread in the initial planet-forming material, as seen in the compositions of nearby stars. A range in Na abundances in the pollutant material is attributed to a range in formation temperatures from below 1,000 K to higher than 1,400 K, suggesting that pollutant material arrives in white dwarf atmospheres from a variety of radial locations. We also find that Solar System-like differentiation is common place in exo-planetary systems. Extreme siderophile (Fe, Ni or Cr) abundances in 8 systems require the accretion of a core-rich fragment of a larger differentiated body to at least a 3σ significance, whilst one system shows evidence that it accreted a crust-rich fragment. In systems where the abundances suggest that accretion has finished (13/202), the total mass accreted can be calculated. The 13 systems are estimated to have accreted masses ranging from the mass of the Moon to half that of Vesta. Our analysis suggests that accretion continues for 11Myrs on average.


Author(s):  
A. Grandjean ◽  
A.-M. Lagrange ◽  
N. Meunier ◽  
P. Rubini ◽  
S. Desidera ◽  
...  
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