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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 1,153 records · Page 64
All sourcesNASA NTRSDOE OSTI
NASA NTRS1983

On the nature of two gamma bursts with spectral evolutions observed by the KONUS experiment

Several unique features of the evolving spectra of the April 2, 1979B, and November 11, 1979 gamma-ray bursts observed by the Konus experiment can be used to determine a number of critical parameters of the sources, within the context of the thermal synchrotron model, including their luminosity distance. These results shed much light on the origin of these events and possibly gamma bursts in general. Previously announced in STAR as N83-14057

Liang, E. P.↗
NASA NTRS2004

The Swift MlDEX Mission

Swift is a NASA MIDEX mission that is in development for launch in 2004. It is a multiwavelength observatory for transient astronomy. The goals of the mission are to determine the origin of gamma-ray bursts and their afterglows and use bursts to probe the early Universe. The mission will also perform a hard x-ray survey at the 1 milliCrab level and will continuously monitor the sky for transients. A wide- field gamma-ray camera will detect more than a hundred GRBs per year to 3 times fainter than BATSE. Sensitive narrow-field X-ray and Uv/optical telescopes will be pointed at the burst location in 20 to 70 sec by an autonomously controlled "swift" spacecraft. For each burst, arcsec positions will be determined and optical/W/X-ray/gamma-ray spectrophotometry performed. The instrumentation is a combination of existing flight-spare hardware and design from XMM and Spectrum-X/JET-X contributed by collaborators in the UX and Italy and development of a coded-aperture camera with a large-area (-0.5 square meter) CdZnTe detector array. The ground station in Malindi is contributed by the Italian Space Agency. The instruments have now completed their fabrication phase and are currently being integrated on the observatory for final testing. up and outreach programs to engage the astronomical community and public in Swift.

Gehrels, Neil↗
DOE OSTI2021

Broadband X-ray burst spectroscopy of the fast-radio-burst-emitting Galactic magnetar

Magnetars are young, magnetically powered neutron stars that possess the strongest magnetic fields in the Universe. Fast radio bursts (FRBs) are extremely intense millisecond-long radio pulses of primarily extragalactic origin, and a leading attribution for their genesis focuses on magnetars. A hallmark signature of magnetars is their emission of bright, hard X-ray bursts of sub-second duration. On 27 April 2020, the Galactic magnetar SGR J1935+2154 emitted hundreds of X-ray bursts within a few hours. One of these temporally coincided with an FRB, the first known detection of an FRB from the Milky Way. Here, we present spectral and temporal analyses of 24 X-ray bursts emitted 13 hours prior to the FRB and seen simultaneously with the Neutron Star Interior Composition Explorer (NICER) mission of the National Aeronautics and Space Administration and with the Fermi Gamma-ray Burst Monitor (GBM) mission in their combined energy range of 0.2 keV to 30 MeV. These broadband spectra permit direct comparison with the spectrum of the FRB-associated X-ray burst (FRB-X). We demonstrate that all 24 NICER and GBM bursts are very similar temporally to the FRB-X, but strikingly different spectrally. The singularity of the FRB-X burst is perhaps indicative of an uncommon locale for its origin. We suggest that this event originated in quasi-polar open or closed magnetic field lines that extend to high altitudes.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS2009

Multiwavelength Challenges in the Fermi Era

The gamma-ray surveys of the sky by AGILE and the Fermi Gamma-ray Space Telescope offer both opportunities and challenges for multi wavelength and multimessenger studies. Gamma-ray bursts, pulsars, binary sources, flaring Active Galactic Nuclei, and Galactic transient sources are all phenomena that can best be studied with a wide variety of instruments simultaneously or contemporaneously. From the gamma-ray side, a principal challenge is the latency from the time of an astrophysical event to the recognition of this event in the data. Obtaining quick and complete multiwavelength coverage of gamma-ray sources of interest can be difficult both in terms of logistics and in terms of generating scientific interest.

Thompson, D. J.↗
NASA NTRS2010

Multiwavelength Challenges in the Fermi Era

The gamma-ray surveys of the sky by AGILE and the Fermi Gamma-ray Space Telescope offer both opportunities and challenges for multiwavelength and multi-messenger studies. Gamma-ray bursts, pulsars, binary sources, flaring Active Galactic Nuclei, and Galactic transient sources are all phenomena that can best be studied with a wide variety of instruments simultaneously or contemporaneously. From the gamma-ray side, a principal challenge is the latency from the time of an astrophysical event to the recognition of this event in the data. Obtaining quick and complete multiwavelength coverage of gamma-ray sources of interest can be difficult both in terms of logistics and in terms of generating scientific interest.

Thompson, D. J.↗
NASA NTRS2021

Broadband X-ray burst spectroscopy of the fast-radio-burst-emitting Galactic magnetar

Magnetars are young, magnetically powered neutron stars that possess the strongest magnetic fields in the Universe. Fast radio bursts (FRBs) are extremely intense millisecond-long radio pulses of primarily extragalactic origin, and a leading attribution for their genesis focuses on magnetars. A hallmark signature of magnetars is their emission of bright, hard X-ray bursts of sub-second duration. On 27 April 2020, the Galactic magnetar SGR J1935+2154 emitted hundreds of X-ray bursts within a few hours. One of these temporally coincided with an FRB, the first known detection of an FRB from the Milky Way. Here, we present spectral and temporal analyses of 24 X-ray bursts emitted 13 hours prior to the FRB and seen simultaneously with the Neutron Star Interior Composition Explorer (NICER) mission of the National Aeronautics and Space Administration and with the Fermi Gamma-ray Burst Monitor (GBM) mission in their combined energy range of 0.2 keV to 30 MeV. These broadband spectra permit direct comparison with the spectrum of the FRB-associated X-ray burst (FRB-X). We demonstrate that all 24 NICER and GBM bursts are very similar temporally to the FRB-X, but strikingly different spectrally. The singularity of the FRB-X burst is perhaps indicative of an uncommon locale for its origin. We suggest that this event originated in quasi-polar open or closed magnetic field lines that extend to high altitudes.

G. Younes↗
NASA NTRS2002

Large Coded Aperture Mask for Spaceflight Hard X-ray Images

The 2.6 square meter coded aperture mask is a vital part of the Burst Alert Telescope on the Swift mission. A random, but known pattern of more than 50,000 lead tiles, each 5 mm square, was bonded to a large honeycomb panel which projects a shadow on the detector array during a gamma ray burst. A two-year development process was necessary to explore ideas, apply techniques, and finalize procedures to meet the strict requirements for the coded aperture mask. Challenges included finding a honeycomb substrate with minimal gamma ray attenuation, selecting an adhesive with adequate bond strength to hold the tiles in place but soft enough to allow the tiles to expand and contract without distorting the panel under large temperature gradients, and eliminating excess adhesive from all untiled areas. The largest challenge was to find an efficient way to bond the > 50,000 lead tiles to the panel with positional tolerances measured in microns. In order to generate the desired bondline, adhesive was applied and allowed to cure to each tile. The pre-cured tiles were located in a tool to maintain positional accuracy, wet adhesive was applied to the panel, and it was lowered to the tile surface with synchronized actuators. Using this procedure, the entire tile pattern was transferred to the large honeycomb panel in a single bond. The pressure for the bond was achieved by enclosing the entire system in a vacuum bag. Thermal vacuum and acoustic tests validated this approach. This paper discusses the methods, materials, and techniques used to fabricate this very large and unique coded aperture mask for the Swift mission.

Vigneau, Danielle N.↗
NASA NTRS1989

The BATSE experiment on the Gamma Ray Observatory: Solar flare hard x ray and gamma-ray capabilities

The Burst and Transient Source Experiment (BATSE) for the Gamma Ray Observatory (GRO) consists of eight detector modules that provide full-sky coverage for gamma-ray bursts and other transient phenomena such as solar flares. Each detector module has a thin, large-area scintillation detector (2025 sq cm) for high time-resolution studies, and a thicker spectroscopy detector (125 sq cm) to extend the energy range and provide better spectral resolution. The total energy range of the system is 15 keV to 100 MeV. These 16 detectors and the associated onboard data system should provide unprecedented capabilities for observing rapid spectral changes and gamma-ray lines from solar flares. The presence of a solar flare can be detected in real-time by BATSE; a trigger signal is sent to two other experiments on the GRO. The launch of the GRO is scheduled for June 1990, so that BATSE can be an important component of the Max '91 campaign.

Fishman, G. J.↗
NASA NTRS2004

The Imminent Swift MIDEX Mission

Swift is a NASA MIDEX mission that is in development for launch in Fall 2004. It is a multiwavelength observatory for transient astronomy. The goals of the mission are to determine the origin of gamma-ray bursts and their afterglows and use bursts to probe the early Universe. The mission will also perform a hard x-ray survey at the 1 milliCrab level and will continuously monitor the sky for transients. A wide-field gamma-ray camera will detect more than a hundred GRBs per year to 3 times fainter than BATSE. Sensitive narrow-field X-ray and UV/optical telescopes will be pointed at the burst. location in 20 to 70 sec by an autonomously controlled "swift" spacecraft. For each burst, arcsec positions will be determined and optical/UV/X-ray/gamma-ray spectrophotometry performed. The instrumentation is a combination of existing flight-spare hardware and design from XMM and Spectrum-X/JET-X contributed by collaborators in the UK and Italy and development of a coded-aperture camera with a large-area (approximately 0.5 square meter) CdZnTe detector array. The ground station in Malindi is contributed by the Italian Space Agency. The instruments have now completed their fabrication phase and are currently being integrated on the observatory for final testing. Key components of the mission are vigorous follow-up and outreach programs to engage the astronomical community and public in Swift.

Gehrels, Neil↗
NASA NTRS2010

The Swift/Fermi GRB 080928 from 1 eV to 150 keV

We present the results of a comprehensive study of the Gamma-Ray Burst 080928 and of its afterglow. GRB 08092 was a long burst detected by Swift/BAT and Fermi/GBM, It is one of the exceptional cases where optical emission was already detected when the GRB itself was still radiating in the gamma-ray band. for nearly 100 seconds simultaneous optical X-ray and gamma-ray data provide a coverage of the spectral energy distribution of the transient source from about 1 eV to 150 keV. Here we analyze the prompt emission, constrain its spectral propertIes. and set lower limits on the initial Lorentz factor of the relativistic outflow, In particular. we show that the SED during the main prompt emission phase is in agreement with synchrotron radiation. We construct the optical/near-infrared light curve and the spectral energy distribution based on Swift/UVOT. ROTSE-Illa (Australia) and GROND (La Silla) data and compare it to the X-ray light curve retrieved from the Swift/XRT repository. We show that its bumpy shape can be modeled by multiple energy injections into the forward shock. Furthermore, we provide evidence that the temporal and spectral evolution of the first strong flare seen in the early X-ray light curve can be explained by large-angle emission. Finally, we report on the results of our search for the GRB host galaxy, for which only a deep upper limit can be provided.

Sonbas, Eda↗
NASA NTRS1987

The gamma-ray spectrometer experiment on the solar maximum mission satellite

The major activities summarized include: Gamma-Ray Spectrometer (GRS) instrument response and flight operation; solar flare studies; cosmic gamma-ray studies; summary of computer operations; search for flare-precursor protons; diffuse galactic annihilation radiation; cosmic ray bursts; atmospheric gamma ray spectrum; gamma ray line emission from supernovae and novae; improved angular resolutions using Earth occultation; and production processing of NASA IPD data. In addition, an updated list of published papers and invited papers or contributed papers presented at scientific meetings is provided.

Chupp, E. L.↗
NASA NTRS1992

Highlights of the theoretical work reported at the workshop

A brief overview is given of the theoretical work done on gamma-ray bursts (GRBs) done in this workshop. Papers on energy source models, optical transients, X-ray and gamma-ray continuum models, and cyclotron line models are reviewed.

Lamb, D. Q.↗
NASA NTRS2012

Reconstructing the Gamma-Ray Photon Optical Depth of the Universe To Z Approx. 4 from Multiwavelength Galaxy Survey Data

Reconstructing the Gamma-Ray Photon Optical Depth of the Universe To Z Approx. 4fFrom Multiwavelength Galaxy Survey Data We reconstruct the gamma-ray opacity of the universe out to z approx. < 3–4 using an extensive library of 342 observed galaxy luminosity function (LF) surveys extending to high redshifts .We cover the whole range from UV to mid-IR (0.15–25 micron ) providing for the first time a robust empirical calculation of the gamma gamma optical depth out to several TeV. Here, we use the same database as Helgason et al. where the extragalactic background light was reconstructed from LFs out to 4.5 micron and was shown to recover observed galaxy counts to high accuracy. We extend our earlier library Of LFs to 25micron such that it covers the energy range of pair production with gamma -rays (1) in the entire Fermi/LAT energy range, and (2) at higher TeV energies probed by ground-based Cherenkov telescopes. In the absence of significant contributions to the cosmic diffuse background from unknown populations, such as the putative Population III era sources, the universe appears to be largely transparent to gamma-rays at all Fermi/LAT energies out to z approx.. 2 whereas it becomes opaque to TeV photons already at z approx. < 0.2 and reaching tau approx∼ 10 at z = 1. Comparing with the currently available Fermi/LAT gamma-ray burst and blazar data shows that there is room for significant emissions originating in the first stars era.

galaxies:evolution↗
NASA NTRS2010

NASA Goddard Space Flight Center, on Behalf of the Fermi Large Area Telescope Collaboration

Because high-energy gamma rays can be produced by processes that also produce neutrinos, the gamma-ray survey of the sky by the Fermi (Gamma-ray Space Telescope offers a view of potential targets for neutrino observations. Gamma-ray bursts. Active Galactic Nuclei, and supernova remnants are all sites where hadronic, neutrino-producing interactions are plausible. Pulsars, pulsar wind nebulae, and binary sources are all phenomena that reveal leptonic particle acceleration through their gamma-ray emission. While important to gamma-ray astrophysics, such sources are of less interest to neutrino studies. This talk will present a broad overview of the constantly changing sky seen with the Large Area Telescope (LAT)on the Fermi spacecraft.

Thompson, David J.↗
NASA NTRS2011

Fermi Gamma-Ray Space Telescope: Highlights of the GeV Sky

Because high-energy gamma rays can be produced by processes that also produce neutrinos. the gamma-ray survey of the sky by the Fermi Gamma-ray Space Telescope offers a view of potenl ial targds for neutrino observations. Gamma-ray bursts. active galactic nuclei, and supernova remnants are all sites where hadronic, neutrino-producing interactions are plausible. Pulsars, pulsar wind nebulae, and binary sources are all phenomena that reveal leptonic particle acceleration through their gamma-ray emission. \Vhile important to gamma-ray astrophysics. such sources are of less interest to neutrino studies. This talk will present a broad overview of the constantly changing sky seen with the Large Area Telescope (LAT) on the Fermi spacecraft.

Thomspon, D. J.↗
NASA NTRS2011

When A Standard Candle Flickers

The Crab Nebula is the only hard X-ray source in the sky that is both bright enough and steady enough to be easily used as a standard candle. As a result, it has been used as a normalization standard by most X-ray/gamma ray telescopes. Although small-scale variations in the nebula are well-known, since the start of science operations of the Fermi Gamma-ray Burst Monitor (GBM) in August 2008 a 7% (70 mcrab) decline has been observed in the overall Crab Nebula flux in the 15-50 keV band, measured with the Earth occultation technique. This decline is independently confirmed in the 15-50 keV band with three other instruments: the Swift Burst Alert Telescope (Swift/BAT), the Rossi X-ray Timing Explorer Proportional Counter Array (RXTE/PCA), and the INTErnational Gamma-Ray Astrophysics Laboratory Imager on Board INTEGRAL (IBIS). A similar decline is also observed in the 3 - 15 keV data from the RXTE/PCA and in the 50 - 100 keV band with GBM, Swift/BAT, and INTEGRAL/IBIS. The change in the pulsed flux measured with RXTE/PCA since 1999 is consistent with the pulsar spin-down, indicating that the observed changes are nebular. Correlated variations in the Crab Nebula flux on a 3 year timescale are also seen independently with the PCA, BAT, and IBIS from 2005 to 2008, with a flux minimum in April 2007. As of August 2010, the current flux has declined below the 2007 minimum.

Wilson-Hodge, Colleen A.↗
NASA NTRS2006

Observations of High-Energy Phenomena with Swift and GLAST

The Swift and CLAST missions promise a great increase in our understanding of the gamma-ray universe. Swift was launched in November 2004 with a primary objective to study gamma-ray bursts. All instruments are performing well and more than 100 GRBs have been studied in detail. Major advances have already been made in the areas of short bursts, high redshift events and afterglow physics. The CLAST mission is scheduled for launch in fall 2007. It features a large new-technology instrument for high energy gamma-ray observations. Thousands of sources will be detected over a 5-10 year lifetime leading to the huge step forward in studies of the energetic gamma-ray sky.

Gehrels, Neil↗
NASA NTRS1992

BATSE analysis techniques for probing the GRB spatial and luminosity distributions

The Burst And Transient Source Experiment (BATSE) has measured homogeneity and isotropy parameters from an increasingly large sample of observed gamma-ray bursts (GRBs), while also maintaining a summary of the way in which the sky has been sampled. Measurement of both of these are necessary for any study of the BATSE data statistically, as they take into account the most serious observational selection effects known in the study of GRBs: beam-smearing and inhomogeneous, anisotropic sky sampling. Knowledge of these effects is important to analysis of GRB angular and intensity distributions. In addition to determining that the bursts are local, it is hoped that analysis of such distributions will allow boundaries to be placed on the true GRB spatial distribution and luminosity function. The technique for studying GRB spatial and luminosity distributions is direct. Results of BATSE analyses are compared to Monte Carlo models parameterized by a variety of spatial and luminosity characteristics.

Hakkila, Jon↗