scholarly journals Search for small trans-Neptunian objects by the TAOS project

2006 ◽  
Vol 2 (S236) ◽  
pp. 65-68 ◽  
Author(s):  
W.P. Chen ◽  
C. Alcock ◽  
T. Axelrod ◽  
F.B. Bianco ◽  
Y.I. Byun ◽  
...  
Keyword(s):  
Solar System ◽  
Detection Rate ◽  
Light Curves ◽  
Wide Field ◽  
Stellar Photometry ◽  
Stellar Occultation ◽  
Icy Bodies ◽  
Photometric Measurements ◽  
Readout Scheme ◽  
Effective Analysis

AbstractThe Taiwan-America Occultation Survey (TAOS) aims to determine the number of small icy bodies in the outer reach of the Solar System by means of stellar occultation. An array of 4 robotic small (D=0.5 m), wide-field (f/1.9) telescopes have been installed at Lulin Observatory in Taiwan to simultaneously monitor some thousand of stars for such rare occultation events. Because a typical occultation event by a TNO a few km across will last for only a fraction of a second, fast photometry is necessary. A special CCD readout scheme has been devised to allow for stellar photometry taken a few times per second. Effective analysis pipelines have been developed to process stellar light curves and to correlate any possible flux changes among all telescopes. A few billion photometric measurements have been collected since the routine survey began in early 2005. Our preliminary result of a very low detection rate suggests a deficit of small TNOs down to a few km size, consistent with the extrapolation of some recent studies of larger (30–100 km) TNOs.

An investigation of Pluto’s troposphere using stellar occultation light curves and an atmospheric radiative–conductive–convective model

Icarus ◽  
2011 ◽  
Vol 214 (2) ◽  
pp. 685-700 ◽  
Author(s):  
Angela M. Zalucha ◽  
Xun Zhu ◽  
Amanda A.S. Gulbis ◽  
Darrell F. Strobel ◽  
J.L. Elliot
Keyword(s):  
Light Curves ◽  
Stellar Occultation ◽  
Convective Model

scholarly journals Image Sensory Experience of Artistic Design Based on the Role of Omnidirectional Vision Sensors

2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Zhen Tong
Keyword(s):  
Detection Rate ◽  
Information Dissemination ◽  
Sensory Experience ◽  
Image Texture ◽  
Omnidirectional Vision ◽  
Wide Field ◽  
Vision Sensor ◽  
Visual Sensor ◽  
Sensory Experiences ◽  
Art Design

As a sensor with a wide field of view, the panoramic vision sensor is efficient and convenient in perceiving the characteristic information of the surrounding environment and plays an important role in the experience of artistic design of images. The transformation of visual and other sensory experiences in art design is to integrate sound, image, texture, taste, and smell with each other through reasonable rules, to create more excellent crossborder art design works. To improve the sensory experience that art design works bring to the audience, the combination of vision and other sensory experiences can maximize the advantages of multiple information dissemination methods and combine the omnidirectional visual sensor with the sensory experience of art design images. In the method part, this article introduces the omnidirectional vision sensor, art design image, and sensory experience modes and content and introduces the hyperbolic concave mirror theory and the Micusik perspective projection imaging model. In the experimental part, the experimental environment, experimental objects, and experimental procedures of this article are introduced. In the analysis part, this article analyzes the six aspects of image database dependency test, performance, comparison of different distortion types, false detection rate and missing detection rate, algorithm time-consuming comparison, sensory experience analysis, and feature point screening. Among the feelings of the art design image, for the first image, 87.21% of the audience’s feelings are happy, indicating that the main idea of this image can bring joy to people. In the second image, the audience’s feelings are mostly sad. For the third image, more than half of the audience’s feelings are melancholy. For the fourth image, 69.34% of the audience’s inner feelings are calm. It explains that the difference in the content of art design images can bring different sensory experiences to people.

Solar system astrometry, Gaia, and the large surveys – a huge step ahead to stellar occultations by distant small solar system bodies

2017 ◽  
Vol 12 (S330) ◽  
pp. 397-398
Author(s):  
J. I. B. Camargo ◽  
M. V. Banda-Huarca ◽  
R. L. Ogando ◽  
J. Desmars ◽  
F. Braga-Ribas ◽  
...  
Keyword(s):  
Solar System ◽  
Outer Solar System ◽  
Stellar Occultation ◽  
Stellar Occultations ◽  
Solar System Bodies

AbstractThe stellar occultation technique is a powerful tool to study distant small solar system bodies. Currently, around 2 500 trans-neptunian objects (TNOs) and Centaurs are known. With the astrometry from Gaia and large surveys like the Large Synoptic Survey Telescope (LSST), accurate predictions of occultation events will be available to tens of thousands of TNOs and Centaurs and boost the knowledge of the outer solar system.

Merging Data from Large and Small Telescopes – Good or Bad? And: How Useful is the Application of Statistical Weights to Time-Series Photometric Measurements?

2003 ◽  
Vol 12 (2) ◽  
Author(s):  
G. Handler
Keyword(s):  
Fourier Transforms ◽  
Light Curves ◽  
Data Sets ◽  
Effective Number ◽  
Spectral Window ◽  
Light Gathering Power ◽  
Data Weighting ◽  
Light Gathering ◽  
Data Points ◽  
Photometric Measurements

AbstractI have investigated the value of the contribution of small telescopes to the success of a whole WET run. To this end, I have applied different data weighting schemes to two extreme WET test data sets. I find that weights proportional to the inverse local scatter in the light curves produce Fourier Transforms of best signal-to-noise. Weighting data stronger than their inverse scatter does not yield optimal results because of the reduction of the effective number of data points.The contribution of the small telescopes to the combined WET results was found to be very important. They do not only improve the spectral window, but they can reduce the noise in the total FT by more than their light gathering power would imply. Some suggestions for the optimal use of small telescopes in the WET are given.

scholarly journals Candidate Periodically Variable Quasars from the Dark Energy Survey and the Sloan Digital Sky Survey

2020 ◽  
Author(s):  
Yu-Ching Chen ◽  
Xin Liu ◽  
Wei-Ting Liao ◽  
A Miguel Holgado ◽  
Hengxiao Guo ◽  
...  
Keyword(s):  
Black Holes ◽  
Dark Energy ◽  
Detection Rate ◽  
Sloan Digital Sky Survey ◽  
Light Curves ◽  
Close Binary ◽  
Single Frequency ◽  
Dark Energy Survey ◽  
Sky Survey ◽  
Energy Survey

Abstract Periodically variable quasars have been suggested as close binary supermassive black holes. We present a systematic search for periodic light curves in 625 spectroscopically confirmed quasars with a median redshift of 1.8 in a 4.6 deg2 overlapping region of the Dark Energy Survey Supernova (DES-SN) fields and the Sloan Digital Sky Survey Stripe 82 (SDSS-S82). Our sample has a unique 20-year long multi-color (griz) light curve enabled by combining DES-SN Y6 observations with archival SDSS-S82 data. The deep imaging allows us to search for periodic light curves in less luminous quasars (down to r ∼23.5 mag) powered by less massive black holes (with masses ≳ 108.5M⊙) at high redshift for the first time. We find five candidates with significant (at >99.74% single-frequency significance in at least two bands with a global p-value of ∼7 × 10−4–3× 10−3 accounting for the look-elsewhere effect) periodicity with observed periods of ∼3–5 years (i.e., 1–2 years in rest frame) having ∼4–6 cycles spanned by the observations. If all five candidates are periodically variable quasars, this translates into a detection rate of ${\sim }0.8^{+0.5}_{-0.3}$% or ${\sim }1.1^{+0.7}_{-0.5}$ quasar per deg2. Our detection rate is 4–80 times larger than those found by previous searches using shallower surveys over larger areas. This discrepancy is likely caused by differences in the quasar populations probed and the survey data qualities. We discuss implications on the future direct detection of low-frequency gravitational waves. Continued photometric monitoring will further assess the robustness and characteristics of these candidate periodic quasars to determine their physical origins.

scholarly journals Extrasolar planet detections with gravitational microlensing

2007 ◽  
Vol 3 (S249) ◽  
pp. 25-30
Author(s):  
Shude Mao ◽  
Eamonn Kerins ◽  
Nicholas J. Rattenbury
Keyword(s):  
Light Curve ◽  
Real Time ◽  
Extrasolar Planets ◽  
Light Curves ◽  
Extrasolar Planet ◽  
Galactic Centre ◽  
Wide Field ◽  
High Magnification ◽  
Gravitational Microlensing

AbstractMicrolensing light curves due to single stars are symmetric and typically last for a month. So far about 4000 microlensing events have been discovered in real-time, the vast majority toward the Galactic centre. The presence of planets around the primary lenses induces deviations in the usual light curve which lasts from hours (for an Earth-mass [M⊕] planet) to days (for a Jupiter-mass [Mj] planet). Currently the survey teams, OGLE and MOA, discover and announce microlensing events in real-time, and follow-up teams (together with the survey teams) monitor selected events intensively (usually with high magnification) in order to identify anomalies caused by planets. So far four extrasolar planets have been discovered using the microlensing technique, with half a dozen new planet candidates identified in 2007 (yet to be published). Future possibilities include a network of wide-field 2m-class telescopes from the ground (which can combine survey and follow-up in the same setup) and a 1m-class survey telescope from space.

scholarly journals Near-Eddington Luminosity Flares from Quiescent Supermassive Black Holes

2009 ◽  
Vol 5 (S267) ◽  
pp. 319-324
Author(s):  
Suvi Gezari
Keyword(s):  
Black Hole ◽  
Thermal Emission ◽  
Rare Event ◽  
Light Curves ◽  
Spectral Energy ◽  
Wide Field ◽  
Tidal Disruption ◽  
X Ray ◽  
Solar Type ◽  
Detection Capabilities

AbstractA dormant supermassive black hole lurking in the center of a galaxy will be revealed when a star passes within its tidal disruption radius, is disrupted, and a flare of electromagnetic radiation is emitted when the bound stellar debris is accreted. Although the tidal disruption of a star is a rare event in a galaxy, ~ 10−4 yr−1, observational candidates have emerged in all-sky X-ray and deep UV surveys in the form of luminous UV/X-ray flares from otherwise quiescent galaxies. We present the light curves and broadband properties of three tidal disruption candidates discovered in the UV by GALEX, and find that (1) the light curves are well-fitted by the power-law decline expected for the fallback of debris from a tidally disrupted solar-type star, and (2) the UV/optical spectral energy distributions can be attributed to thermal emission from an envelope of debris located at ten times the tidal disruption radius of the central black hole. We use the observed peak absolute optical magnitudes of the flares to predict the detection capabilities of the next generation of wide-field optical synoptic surveys.

scholarly journals Classification of ASKAP VAST Radio Light Curves

2011 ◽  
Vol 7 (S285) ◽  
pp. 397-399 ◽  
Author(s):  
Umaa Rebbapragada ◽  
Kitty Lo ◽  
Kiri L. Wagstaff ◽  
Colorado Reed ◽  
Tara Murphy ◽  
...  
Keyword(s):  
Best Practices ◽  
Light Curve ◽  
Field Survey ◽  
Classification Performance ◽  
Light Curves ◽  
Classification Algorithms ◽  
Wide Field ◽  
Radio Transients ◽  
Instrument Sensitivity

AbstractThe VAST survey is a wide-field survey that observes with unprecedented instrument sensitivity (0.5 mJy or lower) and repeat cadence (a goal of 5 seconds) that will enable novel scientific discoveries related to known and unknown classes of radio transients and variables. Given the unprecedented observing characteristics of VAST, it is important to estimate source classification performance, and determine best practices prior to the launch of ASKAP's BETA in 2012. The goal of this study is to identify light-curve characterization and classification algorithms that are best suited for archival VAST light-curve classification. We perform our experiments on light-curve simulations of eight source types and achieve best-case performance of approximately 90% accuracy. We note that classification performance is most influenced by light-curve characterization rather than classifier algorithm.

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