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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.

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At least 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
DOE OSTI2011

SEARCHING FOR THE DRIVING SOURCE OF THE CO MOLECULAR OUTFLOW IN THE HIGH-MASS STAR-FORMING REGION G240.31+0.07

We present low and high angular resolution observations at 1.3, 3.6, and 6 cm obtained from the Very Large Array archive toward the high-mass star formation region G240.31+0.07. We detected, at least, two continuum sources toward G240.31+0.07 at 1.3 cm, which are spatially associated with the millimeter sources MM1 and MM3 reported in the region. Two continuum sources are also detected in the region at 3.6 and 6 cm, spatially coinciding with the millimeter sources MM1 and MM2. We find that the sources MM2 and MM3 seem to be consistent with ultracompact H II regions, harboring B1-0.5 spectral-type zero-age main-sequence stars. Based on the flux density at 1.3, 3.6, and 6 cm, we also find that the spectral index of MM1 is about -0.4, suggesting a combination of thermal and nonthermal emission. In order to search the nature of MM1, we present a detailed comparison of the high angular resolution 6 cm observations of the epochs 1990.3 and 1995.5. The difference image of the two epochs shows variability toward MM1; its flux density and morphology are changing with time. Moreover, a condensation, possibly ejected by MM1 and oriented in the same direction of the CO outflow observed in the region, is also detected. We propose that MM1 is a radio jet and the best candidate to be the driving source of the CO outflow observed in the region.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2012

Pulsar searches of Fermi unassociated sources with the Effelsberg telescope

Using the 100-m Effelsberg radio telescope operating at 1.36 GHz, we have performed a targeted radio pulsar survey of 289 unassociated γ-ray sources discovered by the Large Area Telescope (LAT) aboard the Fermi satellite and published in the 1FGL catalogue (Abdo et al. 2010a). In addition, this survey resulted in the discovery of millisecond pulsar J1745+1017, which resides in a short-period binary system with a low-mass companion, M c,min ~0.0137M⊙, indicative of ‘black widow’ type systems. A 2-yr timing campaign has produced a refined radio ephemeris, accurate enough to allow for phase-folding of the LAT photons, resulting in the detection of a dual-peaked γ-ray light curve, proving that PSR J1745+1017 is the source responsible for the γ-ray emission seen in 1FGL J1745.5+1018 (2FGL J1745.6+1015; Nolan et al. 2012). We find the γ-ray spectrum of PSR J1745+1017 to be well modelled by an exponentially cut-off power law with cut-off energy 3.2 GeV and photon index 1.6. The observed sources are known to contain a further 10 newly discovered pulsars which were undetected in this survey. Our radio observations of these sources are discussed and in all cases limiting flux densities are calculated. Lastly, the reasons behind the seemingly low yield of discoveries are also discussed.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2016

Monte Carlo Bayesian search for the plausible source of the Telescope Array hotspot

The Telescope Array (TA) collaboration has determined a hotspot of 19 ultrahigh-energy cosmic rays (UHECRs). Using a universal model with one source and energy-dependent magnetic deflections, we show that the distribution of the TA hotspot events is consistent with a single source hypothesis, although multiple sources cannot be ruled out. The chance probability of this distribution arising from a homogeneous distribution is 0.2%. We describe here a Monte Carlo Bayesian (MCB) inference approach, which can be used to derive parameters of the magnetic fields as well as the source coordinates, and we apply this method to the TA hotspot data, inferring the location of the likely source. We discuss possible applications of the same approach to future data.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2017

Searching for Compact Radio Sources Associated with UCH ii Regions

Ultra-compact (UC)H ii regions represent a very early stage of massive star formation. The structure and evolution of these regions are not yet fully understood. Interferometric observations showed in recent years that compact sources of uncertain nature are associated with some UCH ii regions. To examine this, we carried out VLA 1.3 cm observations in the A configuration of selected UCH ii regions in order to report additional cases of compact sources embedded in UCH ii regions. With these observations, we find 13 compact sources that are associated with 9 UCH ii regions. Although we cannot establish an unambiguous nature for the newly detected sources, we assess some of their observational properties. According to the results, we can distinguish between two types of compact sources. One type corresponds to sources that are probably deeply embedded in the dense ionized gas of the UCH ii region. These sources are photoevaporated by the exciting star of the region and will last for 10{sup 4}–10{sup 5} years. They may play a crucial role in the evolution of the UCH ii region as the photoevaporated material could replenish the expanding plasma and might provide a solution to the so-called lifetime problem of these regions. The second type of compact sources is not associated with the densest ionized gas of the region. A few of these sources appear resolved and may be photoevaporating objects such as those of the first type, but with significantly lower mass depletion rates. The remaining sources of this second type appear unresolved, and their properties are varied. We speculate on the similarity between the sources of the second type and those of the Orion population of radio sources.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1972

STARSITE Program: Search To Assess Re- sources, Social, Institutional, Technical, and Environmental, toward a decision-making mechanism

The systems approach was used in the seminar on the complex multidisciplinary problem of housing and related environment conditions. The main areas of study are the following; historical overview of housing; diagrammatic presentation of the problem; technological innovations and contributions; management, economic, legal, and political considerations; environment and natural resources; human needs and behavior; model of the housing industry; and potential for implementation. It is felt that a greater attempt should be made to transfer aerospace technology to the housing industry; however, the emphasis of the conference was directed to the modern management techniques developed by NASA. Among the conclusions are the following: The extent and character of the housing problem should be defined. Increased coordination of housing programs within and between Federal agencies is essential. Development of physically sophisticated building systems requires Federal support. New towns of differing life styles need to be created. Physiological and psychological reactions to environmental enclosure need to be defined.

Source record↗
NASA NTRS2004

A Search for the Solar Sources of High-Speed Streams

The original Grant was intended to support backward mapping of the stream structures observed at 1 AU by the WIND spacecraft using the observed wind speeds so that solar sources of the streams could be explored. Realizing that backwards mapping was unlikely to produce reasonable results inside of about 30 Rs, we let a subcontract to Mikic and Linker at SAIC who had developed a MHD code to cover the distance between the lower corona and 30 Rs. We used IPS measurements made by our Co-I Andy Breen to try to establish a correlation between the mapped-back streams and IPS determinations of the stream sources. We report the results of these portions of the program and then explain the progress on studies which were proposed to give insight into stream sources by exploiting the alpha/proton abundance ratios observed from WIND.

Source record↗
DOE OSTI2017

A Search for FRB 121102-like Persistent Radio-luminous Sources—Candidates and Implications for the FRB Rate and Searches

The localization of the repeating fast radio burst (FRB), FRB 121102, suggests that it is associated with a persistent radio-luminous compact source in the FRB host galaxy. Using the FIRST radio catalog, I present a search for luminous persistent sources in nearby galaxies, with radio luminosities >10% of the FRB 121102 persistent source luminosity. The galaxy sample contains about 30% of the total galaxy g-band luminosity within <108 Mpc, in a footprint of 10,600 deg{sup 2}. After rejecting sources likely due to active galactic nuclei activity or background sources, I am left with 11 candidates that are presumably associated with galactic disks or star-formation regions. At least some of these candidates are likely to be due to chance alignment. In addition, I find 85 sources within 1{sup ′′} of galactic nuclei. Assuming that the radio persistent sources are not related to galactic nuclei and that they follow the galaxy g-band light, the 11 sources imply a 95% confidence upper limit on the space density of luminous persistent sources of ≲5×10{sup −5} Mpc{sup −3}, and that at any given time only a small fraction of galaxies host a radio-luminous persistent source (≲10{sup −3} L{sub ∗}{sup −1}). Assuming a persistent source lifetime of 100 years, this implies a birth rate of ≲5×10{sup −7} yr{sup −1} Mpc{sup −3}. Given the FRB volumetric rate, and assuming that all FRBs repeat and are associated with persistent radio sources, this sets a lower limit on the rate of FRB events per persistent source of ≳0.8 yr{sup −1}. I argue that these 11 candidates are good targets for FRB searches and I estimate the FRB event rate from these candidates.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

SEARCHES FOR TIME-DEPENDENT NEUTRINO SOURCES WITH ICECUBE DATA FROM 2008 TO 2012

In this paper searches for flaring astrophysical neutrino sources and sources with periodic emission with the IceCube neutrino telescope are presented. In contrast to time-integrated searches, where steady emission is assumed, the analyses presented here look for a time-dependent signal of neutrinos using the information from the neutrino arrival times to enhance the discovery potential. A search was performed for correlations between neutrino arrival times and directions, as well as neutrino emission following time-dependent light curves, sporadic emission, or periodicities of candidate sources. These include active galactic nuclei, soft γ-ray repeaters, supernova remnants hosting pulsars, microquasars, and X-ray binaries. The work presented here updates and extends previously published results to a longer period that covers 4 years of data from 2008 April 5 to 2012 May 16, including the first year of operation of the completed 86 string detector. The analyses did not find any significant time-dependent point sources of neutrinos, and the results were used to set upper limits on the neutrino flux from source candidates.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2020

Applications and Deployment of Neutron Scatter Cameras in Nuclear Safeguards Scenarios

Neutron scatter cameras (NSCs) are a type of directionally sensitive neutron detector that rely on two consecutive neutron scattering events to localize a source of neutrons. NSCs can be used to locate, image, and identify unknown neutron sources or verify the geometry and identity of known sources. Much technical progress has been made in improving NSC designs, but little literature exists exploring the full range of practical application of neutron scatter cameras. This paper seeks to identify scenarios related to nuclear security and non-proliferation where deployment of NSCs may be useful. These situations could include: limited searches for sources during cargo screening, counting nuclear warheads for treaty verification, verification of special nuclear material during inspections, imaging nuclear contamination, imaging nuclear reactor cores, searching for lost sources, and matching neutron images in shipper/receiver or inventory management scenarios. These scenarios are examined with respect to existing NSC designs and proposed designs in terms of usefulness and practicality of deployment when compared to currently used detection systems.

98 NUCLEAR DISARMAMENT, SAFEGUARDS, AND PHYSICAL P↗
DOE OSTI2016

Contour Mapping Based Radiation Source Localization by UAS Swarm

The unmanned swarm of aerial systems (UAS) can be used for remote radiation sensing and search for source location. Recently, the cost of developing UAS platforms has dropped drastically partly due to the increase in their popularity. The radiation sensing using multiple UAS has becomes economically viable. Different algorithms for determining the location of a radiation source using simultaneous measurements taken from drones in formation have been studied including gradient-based methods. Generally in order to accomplish contour mapping, the swarm of drones with on board sensors use gradient estimation to determine the direction of steepest gradient which governs a bulk heading vector for the swarm to follow. However, some algorithms and test methods are useful only in a specific set of circumstances with particular initial conditions. Besides, implementation of drones in swarm formation was generally not tested in the context of radiation source detection. The objective of this research is to advance the state-of-the-art by conducting experiments using multiple UAS and radiative sources in an indoor flight test-bed. The dynamic flight characteristic of the UAS swarm were considered in the search and mapping algorithms. In this paper, the radiation source detection using algorithms pertaining to swarm formation of UAS, gradient estimation, contour mapping, and experimental flight test-bed are discussed. In addition, more effective and practical ways of constructing the contour maps are explored. (authors)

42 ENGINEERING↗
DOE OSTI2014

Search for a small-scale neutrino anisotropy with three years of IceCube data

The IceCube neutrino observatory built in the antarctic ice offers unique opportunities in studying high energy neutrino emission from Galactic and extragalactic sources. Detecting such neutrino emission could give valuable information about the origin of cosmic rays. Recently, first evidence for a diffuse astrophysical neutrino signal in the PeV range was found with IceCube. There is no clear point source signal yet, and advanced analysis methods are being developed in order to improve the sensitivity to point sources and resolve the diffuse signal into point sources. Other searches like a energy-dependent likelihood scan were already performed on IceCube data. In this paper, we report a complementary search for multiple neutrino point sources from three years of IceCube data, performing an autocorrelation test on the full sky. This analysis is aiming for various faint sources at unknown positions and energy spectra in the sky. The result obtained from this search is consistant with a background-only case and shows an underfluctuation. Here, we present limits using the ansatz of the small-scale anisotropy search.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2017

A 1420 MHz Catalog of Compact Sources in the Northern Galactic Plane

We present a catalog of compact sources of radio emission at 1420 MHz in the northern Galactic plane from the Canadian Galactic Plane Survey. The catalog contains 72,758 compact sources with an angular size less than 3′ within the Galactic longitude range 52° < ℓ < 192° down to a 5 σ detection level of ∼1.2 mJy. Linear polarization properties are included for 12,368 sources with signals greater than 4 σ{sub QU} in the Canadian Galactic Plane Survey (CGPS) Stokes Q and U images at the position of the total intensity peak. We compare CGPS flux densities with cataloged flux densities in the Northern VLA Sky Survey catalog for 10,897 isolated unresolved sources with CGPS flux density greater than 4 mJy to search for sources that show variable flux density on timescales of several years. We identify 146 candidate variables that exhibit high fractional variations between the two surveys. In addition, we identify 13 candidate transient sources that have CGPS flux density above 10 mJy but are not detected in the Northern VLA Sky Survey.

79 ASTRONOMY AND ASTROPHYSICS↗