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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 865 records · Page 48
All sourcesNASA NTRSDOE OSTI
NASA NTRS1997

Radio and Optical Follow-Up Observations and Improved IPN Position of GRB 970111

We report on Westerbork 840 MHz, 1.4 and 5 GHz radio observations of the improved IPN-WFC error box of the gamma ray burst GRB 970111, between 26.4 hours and 120 days after the event onset. In the approximately 16 sq arcmin area defined by the IPN (BATSE and Ulysses) annulus and the published refined BeppoSAX Wide Field Camera (WFC) error box we detected no steady sources brighter than 0.56 mJy (4sigma), and no varying radio emission, down to 1.0 mJy (4sigma). We also report on B, V, R and I band observations of the error box with the 4.2 m William Herschel Telescope at La Palma. Subject headings: gamma rays: bursts - gamma rays: individual (GRB 9701 1 1)

Galama, T. J.↗
NASA NTRS1997

ISPAE Research Highlights 1995-1997

This paper presents ISPAE (Institute for Space Physics, Astrophysics and Education) research highlights from 1995-1997. The topics include: 1) High-Energy Astrophysics (Finding the smoking gun in gamma-ray bursts, Playing peekaboo with gamma ray bursts, and Spectral pulses muddle burst source study, Einstein was right: Black holes do spin, Astronomers find "one-man X-ray band", and Cosmic rays from the supernova next door?); 2) Solar Physics (Bright burst confirms solar storm model, Model predicts speed of solar wind in space, and Angry sunspots snap under the strain); 3) Gravitational Physics; 4) Tether Dynamics; and 5) Space Physics (Plasma winds blow form polar regions, De-SCIFERing thermal electrons, and UVI lets scientists see daytime aurora).

Harwell, Ken↗
NASA NTRS2004

Swift Burst Alert Telescope (BAT) Instrument Response

The Burst Alert Telescope (BAT), a large coded aperture instrument with a wide field-of-view (FOV), provides the gamma-ray burst triggers and locations for the Swift Gamma-Ray Burst Explorer. In addition to providing this imaging information, BAT will perform a 15 keV - 150 keV all-sky hard x-ray survey based on the serendipitous pointings resulting from the study of gamma-ray bursts and will also monitor the sky for transient hard x-ray sources. For BAT to provide spectral and photometric information for the gamma-ray bursts, the transient sources and the all-sky survey, the BAT instrument response must be determined to an increasingly greater accuracy. In this talk, we describe the BAT instrument response as determined to an accuracy suitable for gamma-ray burst studies. We will also discuss the public data analysis tools developed to calculate the BAT response to sources at different energies and locations in the FOV. The level of accuracy required for the BAT instrument response used for the hard x-ray survey is significantly higher because this response must be used in the iterative clean algorithm for finding fainter sources. Because the bright sources add a lot of coding noise to the BAT sky image, fainter sources can be seen only after the counts due to the bright sources are removed. The better we know the BAT response, the lower the noise in the cleaned spectrum and thus the more sensitive the survey. Since the BAT detector plane consists of 32768 individual, 4 mm square CZT gamma-ray detectors, the most accurate BAT response would include 32768 individual detector response functions to separate mask modulation effects from differences in detector efficiencies! We describe OUT continuing work to improve the accuracy of the BAT instrument response and will present the current results of Monte Carlo simulations as well as BAT ground calibration data.

Parsons, A.↗
NASA NTRS1990

What is learned from high energy bursts and flares

The Energetic Gamma Ray Experiment Telescope (EGRET) with its large Nal Total Absorption Shower Counter (TASC) has the scientific capability of performing spectroscopy of high energy cosmic gamma ray bursts and solar flares. EGRET, with a spectroscopy energy range from 0.6 to 140 MeV, provides an opportunity to increase the understanding of the high energy mechanisms of gamma ray bursts and solar flares. A likely interpretation of gamma ray burst sources is that they are rotating, magnetized neutron stars. High magnetic fields can influence the emission of high energy gamma rays, so observational spectroscopic data at high energies can provide information on the upper limits of the magnetic fields in the GRB regions of magnetized neutron stars. Likewise, spectroscopy of high energy gamma rays can provide information useful for deriving the flare proton spectrum which in turn can lead to an understanding of high energy solar flare particle acceleration mechanisms.

Schneid, Edward J.↗
NASA NTRS2016

DDOTI: the Deca-Degree Optical Transient Imager

DDOTI (Deca-Degree Optical Transient Imager) will be a wide-field robotic imager consisting of six 28-centimeter telescopes with prime focus CCDs (Charge-Coupled Devices) mounted on a common equatorial mount. Each telescope will have a field of view of 12 degrees squared, will have 2 arcsec pixels, and will reach a 10 sigma limiting magnitude in 60 seconds of r (redshift) equal to 18.7 in dark time and r (redshift) equal to 18.0 in bright time. The set of six will provide aninstantaneous field of view of about 72 degrees squared. DDOTI uses commercial components almost entirely. The first DDOTI willbe installed at the Observatorio Astronmico Nacional in Sierra San Pedro Martir, Baja California, Mexico in early 2017. The main science goals of DDOTI are the localization of the optical transients associated with GRBs (Gamma Ray Bursts) detected by the GBM (Gamma Ray Burst Monitor) instrument on the Fermi satellite and with gravitational-wave transients. DDOTI will also be used for studies of AGN (Active Galactic Nuclei) and YSO (Young Stellar Object) variability and to determine the occurrence of hot Jupiters. The principal advantage of DDOTI compared to other similar projects is cost: a single DDOTI installation costs only about US $500,000. This makes it possible to contemplate a global network of DDOTI installations. Such geographic diversity would give earlier access and a higher localization rate.We are actively exploring this option.

optical transients↗
NASA NTRS2007

Global Properties of X-Ray Flashes and X-Ray-Rich GRBs Observed by Swift

We describe and discuss the spectral and temporal characteristics of the prompt emission and X-ray afterglow emission of X-ray flashes (XRFs) detected and observed by Swift between December 2005 and September 2006. We compare these characteristics to a sample of X-ray rich gamma-ray bursts (XRRs) and conventional classical gamma-ray bursts (C-GRBs)observed during the same period. We confirm the correlation between Epeak and fluence noted by others and find further evidence that XRFs and C-GRBs form a continuum. We also confirmed that our known redshift samples are consistent with the correlation between the peak energy (Epeak) and the isotropic radiated energy (Eiso), so called the Epeak-Eiso relation. The spectral properties of X-ray afterglows are similar to those of gamma-ray burst afterglows, but the temporal properties of the two classes are quite different. We found that the light curves of C-GRBs afterglow show a break to steeper indices (shallow-to-steep break) at much earlier times than do XRF afterglows. Moreover, the overall luminosity of X-ray afterglows of XRFs are systematically smaller by a factor of two or more compared with that of C-GRBs. These distinct differences in the X-ray afterglow between XRFs and C-GRBs are key to understanding not only a mysterious shallow-to-steep phase in the X-ray afterglow but also the unique nature of XRFs.

Sakamoto, T.↗
NASA NTRS2010

Fermi Gamma-Ray Space Telescope: Science Highlights for the First 8 Months

The Fermi Gamma-ray Space Telescope was launched on June 11, 2008 and since August 2008 has successfully been conducting routine science observations of high energy phenomena in the gamma-ray sky. A number of exciting discoveries have been made during its first year of operation, including blazar flares, high-energy gamma-ray bursts, and numerous new,gamma-ray sources of different types, among them pulsars and Active Galactic Nuclei (AGN). fermi-LAT also performed accurate mea.<;urement of the diffuse gamma-radiation which clarifies the Ge V excess reported by EGRET almost 10 years ago, high precision measurement of the high energy electron spectrum, and other observations. An overview of the observatory status and recent results as of April 30, 2009, are presented. Key words: gamma-ray astronomy, cosmic rays, gamma-ray burst, pulsar, blazar. diffuse gamma-radiation

Moiseev, Alexander↗
NASA NTRS1992

Burst detection capability of the Mars Observer gamma-ray spectrometer

This paper describes the gamma-ray burst detection capability of the gamma-ray spectrometer on board the Mars Observer spacecraft. The instrument is designed to respond to significant bursts by suspending its observation of the Martian surface in favor of optimizing the collection of pre-burst, burst, and post-burst data. The results are expected to contribute to our understanding of gamma-ray bursts through a high energy resolution search for line emission, by the examination of spectral shapes and by comprising one leg of an arrival time network to determine the direction of origin.

Metzger, Albert E.↗
DOE OSTI2021

Pitch-Angle Anisotropy Controls Particle Acceleration and Cooling in Radiative Relativistic Plasma Turbulence

Nature’s most powerful high-energy sources are capable of accelerating particles to high energy and radiating it away on extremely short timescales, even shorter than the light crossing time of the system. It is yet unclear what physical processes can produce such an efficient acceleration, despite the copious radiative losses. By means of radiative particle-in-cell simulations, we show that magnetically dominated turbulence in pair plasmas subject to strong synchrotron cooling generates a nonthermal particle spectrum with a hard power-law range (slope p~1) within a few eddy turnover times. Low pitch-angle particles can significantly exceed the nominal radiation-reaction limit, before abruptly cooling down. The particle spectrum becomes even harder (p<1) over time owing to particle cooling with an energy-dependent pitch-angle anisotropy. The resulting synchrotron spectrum is hard (νF ν ∝ ν s with s~1). Our findings have important implications for understanding the nonthermal emission from high-energy astrophysical sources, most notably the prompt phase of gamma-ray bursts and gamma-ray flares from the Crab nebula.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS1990

Mercuric iodine room temperature gamma-ray detectors

high resolution mercuric iodide room temperature gamma-ray detectors have excellent potential as an essential component of space instruments to be used for high energy astrophysics. Mercuric iodide detectors are being developed both as photodetectors used in combination with scintillation crystals to detect gamma-rays, and as direct gamma-ray detectors. These detectors are highly radiation damage resistant. The list of applications includes gamma-ray burst detection, gamma-ray line astronomy, solar flare studies, and elemental analysis.

Patt, Bradley E.↗
NASA NTRS2000

Future Missions for Gamma-Ray Astronomy

Gamma-ray astronomy has made great advances in recent years, due largely to the recently completed 9-year mission of the Compton Gamma Ray Observatory. In this talk I will give an overview of what advances we may expect in the near future, with particular emphasis on earth-orbiting missions scheduled for flight within the next 5 years. Two missions, the High Energy Transient Explorer and Swift, will provide important new information on the sources of gamma-ray bursts. The Gamma-Ray Large Area Space Telescope will investigate high energy emission from a wide variety of sources, including active galaxies and gamma-ray pulsars. The contributions of ground-based and multiwavelength observations will also be addressed.

Meegan, Charles↗
NASA NTRS2012

Design and Performance of the GAMMA-400 Gamma-Ray Telescope for Dark Matter Searches

The GAMMA-400 gamma-ray telescope is designed to measure the fluxes of gamma-rays and cosmic-ray electrons + positrons, which can be produced by annihilation or decay of the dark matter particles, as well as to survey the celestial sphere in order to study point and extended sources of gamma-rays, measure energy spectra of Galactic and extragalactic diffuse gamma-ray emission, gamma-ray bursts, and gamma-ray emission from the Sun. GAMMA-400 covers the energy range from 100 MeV to 3000 GeV. Its angular resolution is approx. 0.01 deg (E(sub gamma) > 100 GeV), the energy resolution approx. 1% (E(sub gamma) > 10 GeV), and the proton rejection factor approx 10(exp 6). GAMMA-400 will be installed on the Russian space platform Navigator. The beginning of observations is planned for 2018.

Dark Matter↗
NASA NTRS2012

Design and Performance of the GAMMA-400 Gamma-Ray Telescope for Dark Matter Searches

The GAMMA-400 gamma-ray telescope is designed to measure the fluxes of gamma-rays and cosmic-ray electrons (+) positrons, which can be produced by annihilation or decay of the dark matter particles, as well as to survey the celestial sphere in order to study point and extended sources of gamma-rays, measure energy spectra of Galactic and extragalactic diffuse gamma-ray emission, gamma-ray bursts, and gamma-ray emission from the Sun. GAMMA-400 covers the energy range from 100 MeV to 3000 GeV. Its angular resolution is approximately 0.01deg (E(sub gamma) greater than 100 GeV), the energy resolution approximately 1% (E(sub gamma) greater than 10 GeV), and the proton rejection factor approximately 10(exp 6). GAMMA-400 will be installed on the Russian space platform Navigator. The beginning of observations is planned for 2018.

Dark Matter↗
NASA NTRS2007

A Burst Chasing X-ray Polarimeter

Gamma-ray bursts are one of the most powerful explosions in the universe and have been detected out to distances of almost 13 billion light years. The exact origin of these energetic explosions is still unknown but the resulting huge release of energy is thought to create a highly relativistic jet of material and a power-law distribution of electrons. There are several theories describing the origin of the prompt GRB emission that currently cannot be distinguished. Measurements of the linear polarization would provide unique and important constraints on the mechanisms thought to drive these powerful explosions. We present the design of a sensitive, and extremely versatile gamma-ray burst polarimeter. The instrument is a photoelectric polarimeter based on a time-projection chamber. The photoelectric time-projection technique combines high sensitivity with broad band-pass and is potentially the most powerful method between 2 and 100 keV where the photoelectric effect 1s the dominant interaction process We present measurements of polarized and unpolarized X-rays obtained with a prototype detector and describe the two mission concepts, the Gamma-Ray Burst Polarimeter (GRBP) for thc U S Naval Academy satellite MidSTAR-2, and thc Low Energy Polarimeter (LEP) onboard POET, a broadband polarimetry concept for a small explorer mission.

Hill, Joanne E.↗
NASA NTRS1978

X-ray spectrometer experiment aboard the ISEE-C /Heliocentric/ spacecraft

This experiment is designed to provide continuous coverage of solar flare X-ray bursts and transient cosmic gamma-ray bursts. A proportional counter and a scintillation detector together cover the energy range from 5 to 228 keV with good sensitivity, large dynamic range, and high temporal resolution. This experiment provides data storage capability and good absolute timing so that in conjunction with similar experiments on other spacecraft, accurate source locations can be obtained for cosmic gamma-ray bursts.

Anderson, K. A.↗
NASA NTRS1994

Search of the energetic gamma-ray experiment telescope (EGRET) data for high-energy gamma-ray microsecond bursts

Hawking (1974) and Page & Hawking (1976) investigated theoretically the possibility of detecting high-energy gamma rays produced by the quantum-mechanical decay of a small black hole created in the early universe. They concluded that, at the very end of the life of the small black hole, it would radiate a burst of gamma rays peaked near 250 MeV with a total energy of about 10(exp 34) ergs in the order of a microsecond or less. The characteristics of a black hole are determined by laws of physics beyond the range of current particle accelerators; hence, the search for these short bursts of high-energy gamma rays provides at least the possibility of being the first test of this region of physics. The Compton Observatory Energetic Gamma-Ray Experiment Telescope (EGRET) has the capability of detecting directly the gamma rays from such bursts at a much fainter level than SAS 2, and a search of the EGRET data has led to an upper limit of 5 x 10(exp -2) black hole decays per cu pc per yr, placing constraints on this and other theories predicting microsecond high-energy gamma-ray bursts.

Fichtel, C. E.↗
NASA NTRS2008

GRB Studies with Fermi

This slide presentation reviews the studies of Gamma Ray Bursts (GRB) with the Fermi Gamma Ray Space Telescope. Included are pictures of the observatory, with illustrations of the Large Area Telescope (LAT), and the Gamma-ray Burst Monitor (GBM) including information about both their capabilities. Graphs showing the GBM count rate over time after the GBM trigger for three GRBs, preliminary charts showing the multiple detector light curves the spectroscopy of the main LAT peak and the spectral evolution of GRB 080916C Burst Temporally-extended LAT emission.

Meegan, Charles A.↗