Solar astronomy and the Square Kilometer Array Interferometer

2008 ◽  
pp. 207-217
Author(s):  
Robert Braun
Keyword(s):  
Square Kilometer Array ◽  
Solar Astronomy

scholarly journals Multiconjugate Adaptive Optics for Astronomy

2018 ◽  
Vol 56 (1) ◽  
pp. 277-314 ◽  
Author(s):  
François Rigaut ◽  
Benoit Neichel
Keyword(s):  
Adaptive Optics ◽  
Near Infrared ◽  
Phase Reconstruction ◽  
Large Telescope ◽  
Wavefront Sensors ◽  
Error Sources ◽  
New Concepts ◽  
Year 2000 ◽  
Current Systems ◽  
Solar Astronomy

Since the year 2000, adaptive optics (AO) has seen the emergence of a variety of new concepts addressing particular science needs; multiconjugate adaptive optics (MCAO) is one of them. By correcting the atmospheric turbulence in 3D using several wavefront sensors and a tomographic phase reconstruction approach, MCAO aims to provide uniform diffraction limited images in the near-infrared over fields of view larger than 1 arcmin2, i.e., 10 to 20 times larger in area than classical single conjugated AO. In this review, we give a brief reminder of the AO principles and limitations, and then focus on aspects particular to MCAO, such as tomography and specific MCAO error sources. We present examples and results from past or current systems: MAD (Multiconjugate Adaptive Optics Demonstrator) and GeMS (Gemini MCAO System) for nighttime astronomy and the AO system, at Big Bear for solar astronomy. We examine MCAO performance (Strehl ratio up to 40% in H band and full width at half maximum down to 52 mas in the case of MCAO), with a particular focus on photometric and astrometric accuracy, and conclude with considerations on the future of MCAO in the Extremely Large Telescope and post–HST era.

Solar Astronomy Neglected

Science ◽  
1965 ◽  
Vol 147 (3662) ◽  
pp. 1087-1088
Author(s):  
R. Howard ◽  
R. Leighton ◽  
H. Zirin
Keyword(s):  
Solar Astronomy

Pulsar–black hole binaries as a window on quantum gravity

2017 ◽  
Vol 26 (12) ◽  
pp. 1743004 ◽  
Author(s):  
John Estes ◽  
Michael Kavic ◽  
Matthew Lippert ◽  
John H. Simonetti
Keyword(s):  
Quantum Gravity ◽  
Laser Interferometer ◽  
Mean Square ◽  
Mean Square Deviation ◽  
Space Antenna ◽  
Gravitational Effects ◽  
Arrival Times ◽  
Black Hole Binaries ◽  
Laser Interferometer Space Antenna ◽  
Square Kilometer Array

Pulsars (PSRs) are some of the most accurate clocks found in nature, while black holes (BHs) offer a unique arena for the study of quantum gravity. As such, PSR–BH binaries provide ideal astrophysical systems for detecting effects of quantum gravity. With the success of aLIGO and the advent of instruments like the Square Kilometer Array (SKA) and Evolved Laser Interferometer Space Antenna (eLISA), the prospects for discovery of such PSR–BH binaries are very promising. We argue that PSR–BH binaries can serve as ready-made testing grounds for proposed resolutions to the BH information paradox. We propose using timing signals from a PSR beam passing through the region near a BH event horizon as a probe of quantum gravitational effects. In particular, we demonstrate that fluctuations of the geometry outside a BH lead to an increase in the measured root-mean-square deviation of arrival times of PSR pulsar traveling near the horizon.

scholarly journals ConvoSource: Radio-Astronomical Source-Finding with Convolutional Neural Networks

Galaxies ◽  
2019 ◽  
Vol 8 (1) ◽  
pp. 3
Author(s):  
Vesna Lukic ◽  
Francesco de Gasperin ◽  
Marcus Brüggen
Keyword(s):  
Deep Learning ◽  
Galactic Nuclei ◽  
Correlated Noise ◽  
Artificial Data ◽  
Star Forming ◽  
Gaussian Fitting ◽  
Fitting Method ◽  
Novel Method ◽  
Square Kilometer Array ◽  
Total Integration

Finding and classifying astronomical sources is key in the scientific exploitation of radio surveys. Source-finding usually involves identifying the parts of an image belonging to an astronomical source, against some estimated background. This can be problematic in the radio regime, owing to the presence of correlated noise, which can interfere with the signal from the source. In the current work, we present ConvoSource, a novel method based on a deep learning technique, to identify the positions of radio sources, and compare the results to a Gaussian-fitting method. Since the deep learning approach allows the generation of more training images, it should perform well in the source-finding task. We test the source-finding methods on artificial data created for the data challenge of the Square Kilometer Array (SKA). We investigate sources that are divided into three classes: star forming galaxies (SFGs) and two classes of active galactic nuclei (AGN). The artificial data are given at two different frequencies (560 MHz and 1400 MHz), three total integration times (8 h, 100 h, 1000 h), and three signal-to-noise ratios (SNRs) of 1, 2, and 5. At lower SNRs, ConvoSource tends to outperform a Gaussian-fitting approach in the recovery of SFGs and all sources, although at the lowest SNR of one, the better performance is likely due to chance matches. The Gaussian-fitting method performs better in the recovery of the AGN-type sources at lower SNRs. At a higher SNR, ConvoSource performs better on average in the recovery of AGN sources, whereas the Gaussian-fitting method performs better in the recovery of SFGs and all sources. ConvoSource usually performs better at shorter total integration times and detects more true positives and misses fewer sources compared to the Gaussian-fitting method; however, it detects more false positives.

scholarly journals A universal 21 cm signature of growing massive black holes in the early Universe

2019 ◽  
Author(s):  
S Sazonov ◽  
I Khabibullin
Keyword(s):  
Black Holes ◽  
Early Universe ◽  
Generation X ◽  
Mass Range ◽  
Gravitational Potential Energy ◽  
Next Generation ◽  
Massive Black Holes ◽  
X Ray ◽  
Extreme Uv ◽  
Square Kilometer Array

Abstract There is a hope that looking into the early Universe with next-generation telescopes, one will be able to observe the early accretion growth of supermassive black holes (BHs) when their masses were ∼104–106M⊙. According to the standard accretion theory, the bulk of the gravitational potential energy released by radiatively efficient accretion of matter onto a BH in this mass range is expected to be emitted in the extreme UV–ultrasoft X-ray bands. We demonstrate that such a ’miniquasar’ at z ∼ 15 should leave a specific, localized imprint on the 21 cm cosmological signal. Namely, its position on the sky will be surrounded by a region with a fairly sharp boundary of several arcmin radius, within which the 21 cm brightness temperature quickly grows inwards from the background value of ∼−250 mK to ∼+30 mK. The size of this region is only weakly sensitive to the BH mass, so that the flux density of the excess 21 cm signal is expected to be ∼0.1–0.2 mJy at z ∼ 15 and should be detectable by the Square Kilometer Array. We argue that an optimal strategy would be to search for such signals from high-z miniquasar candidates that can be found and localized with a next-generation X-ray mission such as Lynx. A detection of the predicted 21 cm signal would provide a measurement of the growing BH’s redshift to within Δz/(1 + z) ≲ 0.01.

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