Search NASA⌕ Search

SEARCH · Search NASA

Results for “radio detection”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 577 records · Page 32
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Search and identification of transient and variable radio sources using MeerKAT observations: a case study on the MAXI J1820+070 field

ABSTRACT Many transient and variable sources detected at multiple wavelengths are also observed to vary at radio frequencies. However, these samples are typically biased towards sources that are initially detected in wide-field optical, X-ray, or gamma-ray surveys. Many sources that are insufficiently bright at higher frequencies are therefore missed, leading to potential gaps in our knowledge of these sources and missing populations that are not detectable in optical, X-rays, or gamma-rays. Taking advantage of new state-of-the-art radio facilities that provide high-quality wide-field images with fast survey speeds, we can now conduct unbiased surveys for transient and variable sources at radio frequencies. In this paper, we present an unbiased survey using observations obtained by MeerKAT, a mid-frequency (∼GHz) radio array in South Africa’s Karoo Desert. The observations used were obtained as part of a weekly monitoring campaign for X-ray binaries (XRBs) and we focus on the field of MAXI J1820+070. We develop methods to efficiently filter transient and variable candidates that can be directly applied to other data sets. In addition to MAXI J1820+070, we identify four likely active galactic nuclei, one source that could be a Galactic source (pulsar or quiescent XRB) or an AGN, and one variable pulsar. No transient sources, defined as being undetected in deep images, were identified leading to a transient surface density of <3.7 × 10−2 deg−2 at a sensitivity of 1 mJy on time-scales of 1 week at 1.4 GHz.

Rowlinson, A. (ORCID:0000000211957022)↗
DOE OSTI2020

Multiwavelength Observations of 2HWC J1928+177: Dark Accelerator or New TeV Gamma-Ray Binary?

2HWC J1928+177 is a Galactic TeV gamma-ray source detected by the High Altitude Water Cherenkov (HAWC) Observatory up to ~56 TeV. The HAWC source, later confirmed by the High Energy Stereoscopic System, still remains unidentified as a dark accelerator since there is no apparent supernova remnant or pulsar wind nebula detected in the lower-energy bands. The radio pulsar PSR J1928+1746, coinciding with the HAWC source position, has no X-ray counterpart. In this work, our SED modeling shows that inverse Compton scattering in the putative pulsar wind nebula can account for the TeV emission only if the unseen nebula is extended beyond $r\sim 4^{\prime} $. Alternatively, TeV gamma-rays may be produced by hadronic interactions between relativistic protons from an undetected supernova remnant associated with the radio pulsar and a nearby molecular cloud G52.9+0.1. NuSTAR and Chandra observations detected a variable X-ray point source within the HAWC error circle, potentially associated with a bright infrared (IR) source. The X-ray spectra can be fitted with an absorbed power-law model with N H = (9 ± 3) × 10 22 cm –2 and Γ X = 1.6 ± 0.3 and exhibit long-term X-ray flux variability over the last decade. If the X-ray source, possibly associated with the IR source (likely an O star), is the counterpart of the HAWC source, it may be a new TeV gamma-ray binary powered by collisions between the pulsar wind and stellar wind. Follow-up X-ray observations are warranted to search for diffuse X-ray emission and determine the nature of the HAWC source.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2024

Radioimaging for real-time tracking of high-voltage breakdown

Development of a radioimaging diagnostic for high-voltage component reliability testing and electrical breakdown computational model validation is described. Radioimaging has its roots in radio astronomy, where aperture synthesis (also known as synthesis imaging) has been utilized for decades to image radio sources far from Earth. Radioimaging as described herein, in contrast, seeks to image radio sources in close proximity to its receivers (i.e., in a laboratory environment). Here it is shown that corona discharge, a non-destructive precursor to catastrophic (thermal) arc discharge, electromagnetically radiates strongly within a 250 kHz – 2.5 GHz bandwidth, and is readily detected and located by postprocessing the received radio signals. The ability of radioimaging to detect both corona and arc discharge (grouped together herein as high voltage breakdown or HVB) makes it a valuable tool for 100% HVB detection in materials, components, and devices, and has the ability to indicate electrical weakness (via corona detection) prior to a destructive arc discharge event. Radioimaging enables HVB to be located both internal and external to dielectric components under test in near-real-time, with multiple and/or extended HVB events located simultaneously. In contrast, existing non-destructive diagnostics (at the time of this writing) either indicate electrical breakdown without resolving failure locations (e.g., current, voltage, and chemical measurements), locate external HVB (e.g., high-speed optical and ultraviolet (UV) measurements or photography), or locate both external and internal HVB but with low fidelity (e.g., a single HVB source can be located by existing time-of-arrival (TOA) UHF or acoustic emissions). Radioimaging instead creates a sequence of high-fidelity images similar to an optical high-speed camera but at radiofrequencies (RF), and is not limited to two-dimensions. Moreover, radioimaging has already served one internal and two external industry customers, the results of which are detailed in this report. The radioimaging results described herein were part of a three-year effort funded by the Sandia Lab Directed Research and Development (LDRD) program within the Radiation, Electromagnetic, High Energy Density Science (REHEDS) investment area.

47 OTHER INSTRUMENTATION↗
DOE OSTI2022

Discovery of a bright extended X-ray jet in RGB J1512+020A

ABSTRACT We report the discovery of a bright, extended X-ray jet in the quasar RGB J1512+020A (z = 0.22). Chandra observations show the X-ray core and 13 arcsec (∼45 kpc projected) extended emission coincident with the radio jet. The jet stands out as one of brightest X-ray jets (LX ∼ 7 × 1043 erg s−1) at low redshift (z < 0.5) discovered so far, with remarkably large X-ray to radio luminosity ratios (LX/Lr up to ∼50). We identified four main components, two unresolved knots and two extended structures, one being the jet brightest feature (JBF). All jet features are also detected in ALMA archival observations. The radio, sub-mm to X-ray spectra of the two knots can be modelled with a single synchrotron component. For the two resolved structures, the ALMA data unveil a turnover of the low-energy continuum at ∼460 GHz. External Comptonization of cosmic microwave background photons can account for the observed X-ray emission if the jet speed remains highly relativistic, with bulk motion Γbulk > 15, up to tens of kiloparsec from the core. However, the comparison with the spectral energy distribution of similar X-ray detected jets shows that the alternative hypothesis of synchrotron emission from an additional population of ultra-high-energy electrons is also possible. We report a tentative (≳2σ) optical detection of the JBF in images of the Dark Energy Camera Legacy Survey. If confirmed, the optical emission should be either the low-energy tail of the radiative component responsible for the X-ray emission or a third, separate component.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1985

VLA observations of A and B stars with kilogauss magnetic fields

The serendipitous discovery that the star Sigma Ori E is a 3.5 mJy radio continuum source at 6 cm has stimulated a radio survey of other early-type stars with strong magnetic fields. No Ap stars have been detected of the eight observed, with typical 3-sigma upper limits of 0.5 mJy at 2 cm. Of the six Bp stars examined, only HR 1890, a helium-strong star, was detected. Possible emission mechanisms for the observed radio emission are discussed, and it is concluded that nonthermal emission seems the most plausible, on the basis of the present data.

Drake, S. A.↗
NASA NTRS1978

Far-infrared observations of H II regions in M33

Three H II regions in M33, namely, IC 133, NGC 595, and NGC 604, have been observed at far-infrared wavelengths. Only NGC 604, the strongest radio source of the three, was detected. The far-infrared radiation appears to be thermal emission from dust. The amount of dust known to be present in NGC 604 from comparison of optical and radio data is sufficient to account for the observed far-infrared emission. The total power radiated in the far-infrared is comparable to the total luminosity of the exciting stars of the H II region.

Gatley, I.↗
DOE OSTI2022

Improvements to the 115g/115m Cd Nuclear Data

Repeated measurements of the isotope 115m Cd by Los Alamos National Laboratory (LANL), Pacific Northwest National Laboratory (PNNL), and Atomic Weapons Establishment (AWE) have revealed a consistent discrepancy between beta and gamma counting. This suggests that a significant disparity exists between the true value of the isotope’s gamma-ray branching ratios and the values reported by the National Nuclear Data Center (NNDC). Enriched 114 Cd was irradiated using thermal neutrons to produce a high-purity 115m/g Cd source for counting and analysis using traditional singles gamma-ray spectroscopy, liquid scintillation counting, gas-proportional counting, and analysis using the new Gamma-Alpha-Beta-Gamma (GABγ) and Gamma-Alpha-Beta Radio-Isotope EvaLuator (GABRIEL) coincidence detection systems. Using the D-T fusion generated neutrons, reduces the wait time required to let the short-lived 115Cd ground state decay away by leveraging the 1:1 production ratio of the ground and metastable state of 115 Cd from the 115 In (n,p) reaction relative to the 10:1 production ratio of the ground and metastable isotopes of 115 Cd by thermal neutron capture on 114 Cd. However, the much higher flux in from the Washington State University TRIGA reactor is a more rapid method of production of 115m/gCd but requires access to enriched 114 Cd. High purity 115m/g Cd samples were analyzed on regular intervals over a period of 140-days. The activity of 115m Cd measured by beta and gamma show a clear discrepancy using the current best known gamma-ray decay branching ratios. Based on these observations and measurements, a set of new branching ratio recommendations have been produced using conventional counting techniques and the advanced GAB? and GABRIEL instruments.

07 ISOTOPE AND RADIATION SOURCES↗
DOE OSTI2020

A Multiwavelength Study of the Cool Core Cluster MACS J1447.4+0827

Clusters of galaxies are outstanding laboratories for understanding the physics of supermassive black hole (SMBH) feedback. Here we present the first Chandra, Karl G. Jansky Very Large Array, and Hubble Space Telescope analysis of MACS J1447.4+0827 (z = 0.3755), one of the strongest cool core clusters known, in which extreme feedback from its central SMBH is needed to prevent the hot intracluster gas from cooling. Using this multiwavelength approach, including 70 ks of Chandra X-ray observations, we detect the presence of collimated jetted outflows that coincide with a southern and a northern X-ray cavity. The total mechanical power associated with these outflows (P {sub cav} ≈ 6 × 10{sup 44} erg s{sup −1}) is roughly consistent with the energy required to prevent catastrophic cooling of the hot intracluster gas (L {sub cool} = 1.71 ± 0.01 × 10{sup 45} erg s{sup −1} for t {sub cool} = 7.7 Gyr), implying that powerful SMBH feedback was in place several Gyr ago in MACS J1447.7+0827. In addition, we detect the presence of a radio minihalo that extends over 300 kpc in diameter (P {sub 1.4GHz} = 3.0 ± 0.3 × 10{sup 24} W Hz{sup −1}). The X-ray observations also reveal an ∼20 kpc plumelike structure that coincides with optical dusty filaments that surround the central galaxy. Overall, this study demonstrates that the various physical phenomena occurring in the most nearby clusters of galaxies are also occurring in their more distant analogs.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1965

The search for extraterrestrial life.

Approaches for analyzing possible life forms on other planets, noting detection of microorganisms or enzymes, radio contact and retracing life in laboratory

LIFE DETECTOR↗
NASA NTRS1974

A high-resolution map of the Orion Nebula region at far-infrared wavelengths

It is shown that the Kleinmann-Low nebula continues to radiate like a 70-deg-K blackbody at 69 microns, as it does at shorter wavelengths, but that most of the 69-micron flux from Ori A (M42) comes from an extended emission that roughly follows the free-free radio emission. Nearby sources also detected include the nebula M43 and the molecular cloud OMC-2.

Fazio, G. G.↗
NASA NTRS1977

Investigation of possible lower hybrid emission from the NASA Lewis bumpy torus plasma

Radio frequency emission has been detected near the power hybrid frequency of a bumpy torus plasma by using a responsive detection system that consists of a spectrum analyzer and a 50 ohm miniature coaxial antenna concentrically located in a re-entrant quartz tube. The frequency shift of a broad emission peak was monitored as a function of background pressure, electrode voltage, and the strength of the dc magnetic field. Simultaneous measurements of the average plasma density were made with a polarization diplexing microwave interferometer. The information derived from the experiment is discussed with particular reference to the following: (1) whether the emissions are dominated by atomic or molecular species of deuterium; (2) the strength of the dc magnetic field in the emitting region; (3) the geometric location of the emitting region of the plasma; (4) comparison of the lower hybrid plasma density with the average plasma density; and (5) relation of ion spoke geometry to lower hybrid emission.

Mallavarpu, R.↗
NASA NTRS1981

Noise and interference study for satellite lightning sensor

The use of radio frequency techniques for the detection and monitoring of terrestrial thunderstorms from space are discussed. Three major points are assessed: (1) lightning and noise source characteristics; (2) propagation effects imposed by the atmosphere and ionosphere; and (3) the electromagnetic environment in near space within which lightning RF signatures must be detected. A composite frequency spectrum of the peak of amplitude from lightning flashes is developed. Propagation effects (ionospheric cutoff, refraction, absorption, dispersion and scintillation) are considered to modify the lightning spectrum to the geosynchronous case. It is suggested that in comparing the modified spectrum with interfering noise source spectra RF lightning pulses on frequencies up to a few GHz are detectable above the natural noise environment in near space.

Herman, J. R.↗
NASA NTRS1980

A study of universal modulation techniques applied to satellite data collection

A universal modulation and frequency control system for use with data collection platform (DCP) transmitters is examined. The final design discussed can, under software/firmwave control, generate all of the specific digital data modulation formats currently used in the NASA satellite data collection service and can simultaneously synthesize the proper RF carrier frequencies employed. A novel technique for DCP time and frequency control is presented. The emissions of NBS radio station WWV/WWVH are received, detected, and finally decoded in microcomputer software to generate a highly accurate time base for the platform; with the assistance of external hardware, the microcomputer also directs the recalibration of all DCP oscillators to achieve very high frequency accuracies and low drift rates versus temperature, supply voltage, and time. The final programmable DCP design also employs direct microcomputer control of data reduction, formatting, transmitter switching, and system power management.

Source record↗
NASA NTRS1984

X-ray spectra and time variability of active galactic nuclei

X ray measurements taken with the HEAO-1 and -2 satellites are examined for clues to the source of emissions from active galactic nuclei (AGN). The data covered the energy range 2-100 keV and 0.5-4.5 keV and encompassed quasars, BL Lac objects, Seyfert I galaxies and broadline radio galaxies. The broadline spectra were best fit with a power law with a slope of about 0.68. The continua displayed roughly equivalent energy at all wavelengths except for radio bands. Spectral variability was detected in the BL Lac objects, which may emit optical, UV and soft X ray radiation from optically thin synchrotron emission with a hard X ray tail from inverse Compton scattering. No strong variability was evidenced with other AGN, suggesting that the emitting regions are below the Eddington luminosity and thus exhibit stable flow characteristics.

Mushotzky, R. F.↗
NASA NTRS1985

Remote sensing technologies for Space Missions in the second half of the nineties' decade

The remote sensing research and technology to be used in the development of future NASA missions are discussed, with consideration given to earth sciences, planetary sciences, solar physics, and astrophysics. The remote sensing missions planned in the four application areas, their payload packages, and the particular instruments that will make up these packages are described. The advanced technologies to be used include systems and devices that address the detection of radiation in the radio, microwave, millimeter wave, submillimeter wave, IR, visible, UV, X-ray, and gamma-ray parts of the spectrum, including supporting technologies, such as optics, liquid cryogen transfer systems, and 'smart' sensors.

Sokoloski, M. M.↗
NASA NTRS1985

Clock synchronization by accelerated observers - Metric construction for arbitrary congruences of world lines

Clock synchronization in an arbitrarily accelerated observer congruence is considered. A general solution is obtained that maintains the isotropy and coordinate independence of the one-way speed of light. Attention is also given to various particular cases including, rotating disk congruence or ring congruence. An explicit, congruence-based spacetime metric is constructed according to Einstein's clock synchronization procedure and the equation for the geodesics of the space-time was derived using Hamilton-Jacobi method. The application of interferometric techniques (absolute phase radio interferometry, VLBI) to the detection of the 'global Sagnac effect' is also discussed.

Henriksen, R. N.↗
NASA NTRS1993

Planets around pulsars; Proceedings of the Conference, California Inst. of Technology, Pasadena, Apr. 30-May 1, 1992

Topics addressed include planets and pulsar timing; timing noise in pulsars and alternative explanations; orbital dynamics; planet formation scenarios; searches for disks and other planets; and comets, planetesimals, and debris disks. Particular attention is given to PSR 1257+12 and its planetary companions; the detectability of planetary companions to radio pulsars; orbital dynamics of PSR 1257+12 and its two planetary companions; formation and evolution of pulsars; the circumstellar environment of the GG Tau multiple system; IRAS sources near positions of pulsars; and gamma-ray bursts from planetesimal accretion.

Phillips, J. A.↗