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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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All sourcesNASA NTRSDOE OSTI
NASA NTRS2007

GLAST, the Gamma-ray Large Area Space Telescope

The Gamma-ray Large Area Space Telescope, GLAST, is a mission to measure the cosmic gamma-ray flux in the energy range 20 MeV to greater than 300 GeV, with supporting measurements for gamma-ray bursts from 10 keV to 25 MeV. With its upcoming launch in 2008, GLAST will open a new and important window on a wide variety of phenomena, including black holes and active galactic nuclei; the optical-UV extragalactic background light, gamma-ray bursts; the origin of cosmic rays and supernova remnants; and searches for hypothetical new phenomena such as supersymmetric dark matter annihilations and Lorentz invariance violation. In addition to the science opportunities, this talk includes a description of the instruments, the collaboration between particle physicists and astrophysicists, the opportunities for guest observers, and the mission status.

Ritz, Steven↗
NASA NTRS2007

GLAST, the Gamma-ray Large Area Space Telescope

The Gamma-ray Large Area Space Telescope, GLAST, is a mission to measure the cosmic gamma-ray flux in the energy range 20 MeV to greater than 300 GeV, with supporting measurements for gamma-ray bursts from 10 keV to 25 MeV. With its upcoming launch in 2008, GLAST will open a new and important window on a wide variety of phenomena, including black holes and active galactic nuclei; the optical-UV extragalactic background light, gamma-ray bursts; the origin of cosmic rays and supernova remnants; and searches for hypothetical new phenomena such as supersymmetric dark matter annihilations and Lorentz invariance violation. In addition to the science opportunities, this talk includes a description of the instruments, the collaboration between particle physicists and astrophysicists, the opportunities for guest observers, and the mission status.

Ritz, Steven↗
NASA NTRS2009

First Year Results from the Fermi Gamma-Ray Space Telescope

After one year of survey observations and more than 70 billion triggers, Fermi is revealing an unprecedented view of the high energy gamma-ray sky. The observatory .carries two instruments, the Gamma-ray Burst Monitor (GB, 8 keV - 40 MeV) and the Large Area Telescope (LAT, 20 MeV greater than or equal to 300 GeV), which in combination cover over 7 orders of magnitude in energy for transient phenomena. The LAT provides substantially more sensitivity than previous instruments in this waveband and has opened up the energy window from 10-100 GeV. The first year has produced many important results, from detections of extremely energetic and distant gamma-ray bursts, to monitoring daily variations in emission caused by massive black holes at the cores of galaxies, to identifying a new population of gamma-ray bright pulsars, to measuring the spectrum of diffuse emission from our own. Galaxy and the spectrum of the local cosmic electrons. I'll review highlights from the first year and discuss how the data are answering questions from the past and raising new ones for the future.

Hays, Elizabeth↗
NASA NTRS2018

Polarimetry in X- and Gamma-Ray Astronomy: The Ultimate Dimension

Polarization has been a powerful diagnostic tool in radio, microwave, and visible astronomy, providing details of photonproduction mechanisms on much smaller scales than can bedirectly imaged or deduced from photon intensity and energyalone. While polarimetry at other these wavebands (radio,microwave, and optical) is an established technique, highenergy astrophysics lags far behind in this respect. Yet polarizationanalysis has the potential of revealing many detailsabout the magnetic fields, geometries, and emission mechanismsfound in high energy emitting sources. Deviations fromspherical symmetry and/or the presence of ordered magneticfields give rise to polarized radiation: some examples includeanisotropy in solar flares, the presence of jets in microquasarsand blazars, accretion disks around stellar and massive blackholes, accreting and rotation-powered pulsars, and beams ingamma-ray bursts. In addition, null polarization detectionsfrom gamma-ray bursts at x-ray energies have been usedas a test of fundamental physics by placing limits on the possibleviolation of Lorentz invariance.

Hunter, Stanley D.↗
NASA NTRS1999

The Structure and Evolution of LOCBURST: The BATSE Burst Location Algorithm

The gamma-ray burst (GRB) location algorithm used to produce the BATSE GRB locations is described. The general flow of control of the current location algorithm is presented, and the significant properties of the various physical inputs required are identified. The development of the burst location algorithm during the releases of the BATSE IB, 2B, and 3B GRB catalogs is presented so that the reasons for the differences in the positions and error estimates between the catalogs can be understood. In particular, differences between the 2B and 3B locations are discussed for events that have moved significantly and the reasons for the changes explained. The locations of bursts located independently by the interplanetary network (IPN) are used to illustrate the effect on burst location accuracy of various components of the algorithm. IPN data and locations from other gamma-ray instruments are used to calculate estimates of the systematic errors on BATSE burst locations.

Pendleton, Geoffrey N.↗
NASA NTRS1991

Neutron stars and the distance to gamma-ray bursters

Assuming that gamma-ray bursts originate from galactic neutron stars, an analytic method for studying their statistical properties is outlined. If a significant fraction of all neutron stars are born with space velocities of less than approximately 100 km/s, as suggested by studies of pulsar statistics, then the sampling distance to gamma-ray burst sources should be less than about several hundred pc. These results have important implications on theories of radio-pulsar evolution and magnetic-field decay.

Dermer, Charles D.↗
DOE OSTI2024

Los Alamos National Laboratory: SULI Appointment

The progenitors of gamma-ray bursts - the brightest explosions in our universe - are still poorly understood. It has been suggested that massive stars collapsing in interacting binary systems (i.e. with a closely orbiting compact object companion) can provide the necessary angular momentum and dense surrounding medium to explain observations of radio-loud gamma-ray bursts. We explore this progenitor system using the population synthesis code COSMIC. We explore the dependence of the properties of an interacting binary systems - including the remnant types and their masses - on metallicity and mass raction of the binary system. We also explore how the rates of populations of these systems depend on metallicity. Our findings help constrain what properties lead to viable GRB progenitors, especially radio loud GRBs.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS2000

[Compton GRO Cycle 7]

The goals of this project were to use the improved location accuracy of combined BATSE/Ulysses-IPN gamma-ray burst (GRB) data to search for small-angle clustering within the burst population and to search for possible correlations between bursts and catalogs of known astrophysical objects. The research was completed in several phases due to the length of time needed to process the basic BATSE/Ulysses data and to develop the appropriate analysis algorithms. In the first phase, BATSE/Ulysses data were gathered from their respective sources and processed to yield, final BATSE burst catalog locations and final BATSE/Ulysses IPN timing annuli. The final data are published. In the next phase, traditional statistical analysis techniques were used to search a subset of the data for small-angle clustering and. correlations, and to produce upper limits. Next, the unique analysis techniques and software described in the proposal were developed and,applied to the final set of data (corresponding to the 4B catalog). The final search did not find any significant self-clustering or correlations with supernovae, AGN, or near by galaxy clusters. The investigation ruled-out earlier findings that indicated (with marginal significance) such results, and. provided stringent limits on the allowable fraction of bursts that are self-clustered and associated with selected known objects. An added benefit of this research came in 1998 when it was suggested that some gamma-ray bursts may be associated with supernova (SN) explosions. We responded rapidly and applied the tools of this investigation to study this possibility. Using combined BATSE/Ulysses data, we were able to completely rule out any association between bright bursts and known supernovae, thereby questioning the validity of any GRB/SN association. If a GRB/SN association exists, it must be only with a small fraction of weak bursts.

Kippen, R. Marc↗
NASA NTRS2020

The Broad-lined Ic Supernova ZTF18aaqjovh (SN 2018bvw): An Optically Discovered Engine-driven Supernova Candidate with Luminous Radio Emission

We present ZTF18aaqjovh (SN 2018bvw), a high-velocity ("broad-lined") stripped-envelope (Type Ic) supernova (Ic-BL SN) discovered in the Zwicky Transient Facility one-day cadence survey. ZTF18aaqjovh shares a number of features in common with engine-driven explosions: the photospheric velocity and the shape of the optical light curve are very similar to those of the Type Ic-BL SN 1998bw, which was associated with a low-luminosity gamma-ray burst (LLGRB) and had relativistic ejecta. However, the radio luminosity of ZTF18aaqjovh is almost two orders of magnitude fainter than that of SN 1998bw at the same velocity phase, and the shock velocity is at most mildly relativistic (v = 0.06–0.4c). A search of high-energy catalogs reveals no compelling gamma-ray burst (GRB) counterpart to ZTF18aaqjovh, and the limit on the prompt GRB luminosity of L(γ(ꙩ)iso) ≈ 1.6 x 10^(48) erg/s excludes a classical GRB but not an LLGRB. Altogether, ZTF18aaqjovh represents another transition event between engine-driven SNe associated with GRBs and "ordinary" Ic-BL SNe.

Anna Y. Q. Ho↗
NASA NTRS2008

GRB Catalog: Bursts from Vela to Swift

Gamma ray burst (GRB) astronomy started when the first event was recorded on July 2, 1967 by Vela 4a and 4b. Since then many missions have flown experiments capable of detecting GRBs. The events collected by these older experiments are mostly available in paper copy, each containing a few ten to a few hundred bursts. No systematic effort in cataloging of these bursts has been available. In some cases the information is unpublished and in others difficult to retrieve. The first major GRB catalog was obtained by GRO with the BATSE experiment. It contains more than 2000 bursts and includes homogeneous information for each of the bursts. With the launch of Swift, the first Gamma-ray/X-ray mission dedicated to the study of GRBs and their afterglows, a wealth of information is collected by the Swift instrument as well as from ground-based telescopes. This talk will describe the efforts to create a comprehensive GRBCAT and its current status and future prospective.

Angelini, L.↗
NASA NTRS2016

Modeling the Swift Bat Trigger Algorithm with Machine Learning

To draw inferences about gamma-ray burst (GRB) source populations based on Swift observations, it is essential to understand the detection efficiency of the Swift burst alert telescope (BAT). This study considers the problem of modeling the Swift / BAT triggering algorithm for long GRBs, a computationally expensive procedure, and models it using machine learning algorithms. A large sample of simulated GRBs from Lien et al. is used to train various models: random forests, boosted decision trees (with AdaBoost), support vector machines, and artificial neural networks. The best models have accuracies of greater than or equal to 97 percent (less than or equal to 3 percent error), which is a significant improvement on a cut in GRB flux, which has an accuracy of 89.6 percent (10.4 percent error). These models are then used to measure the detection efficiency of Swift as a function of redshift z, which is used to perform Bayesian parameter estimation on the GRB rate distribution. We find a local GRB rate density of n (sub 0) approaching 0.48 (sup plus 0.41) (sub minus 0.23) per cubic gigaparsecs per year with power-law indices of n (sub 1) approaching 1.7 (sup plus 0.6) (sub minus 0.5) and n (sub 2) approaching minus 5.9 (sup plus 5.7) (sub minus 0.1) for GRBs above and below a break point of z (redshift) (sub 1) approaching 6.8 (sup plus 2.8) (sub minus 3.2). This methodology is able to improve upon earlier studies by more accurately modeling Swift detection and using this for fully Bayesian model fitting.

gamma-ray burst: general – gamma-rays: general â↗
NASA NTRS1989

High energy flare physics group summary

The contributions of the High Energy Flare Physics Special Session in the American Astronomical Society Solar Physics Division Meeting are reviewed. Oral and poster papers were presented on observatories and instruments available for the upcoming solar maximum. Among these are the space-based Gamma Ray Observatory, the Solar Flare and Cosmic Burst Gamma Ray Experiment on the Ulysses spacecraft, the Soft X Ray Telescope on the spacecraft Solar-A, and the balloon-based Gamma Ray Imaging Device. Ground based observatories with new capabilities include the BIMA mm-wave interferometer (Univ. of California, Berkeley; Univ. of Illinois; Univ. of Maryland), Owens Valley Radio Observatory and the Very Large Array. The highlights of the various instrument performances are reported and potential data correlations and collaborations are suggested.

Ryan, J. M.↗
NASA NTRS1993

Rosat observation of the 4U 1543-47 outburst in 1992

Observation of 4U 1543-47 (HL Lupi) with the Rosat satellite on 21 Aug. 1992 with the PSPC (Position Sensitive Proportional Counter) and on 4 Sep. 1992 with the HRI (High Resolution Imager), four and five months after the soft X-ray transient outburst, respectively, is reported. Both observations revealed the source to be much brighter than expected from the decay rate at harder X-rays (deduced from BATSE (Gamma Ray Burst (GRB) instrument team for the Compton Gamma Ray Observatory) data). BATSE observations in Aug. 1992 do not show any significant increase in the hard X-ray flux, suggesting that the soft and hard X-ray fluxes are either decoupled or anticorrelated to some degree.

Greiner, J.↗
NASA NTRS1993

Rosat and BATSE observations of GRS 1915+105

The determination of an accurate X-ray position of GRS 1915+1405, using a target of opportunity Rosat HRI (High Resolution Imager) observation in Oct. 1992, which allowed deep optical follow up studies, is reported. A spectral fit to Rosat PSPC (Position Sensitive Proportional Counter) and BATSE (Gamma Ray Burst (GRB) instrument team for the Compton Gamma Ray Observatory) observations in Oct. 1992 reveal a steep spectrum with power law index alpha = -3 between 0.5 and 300 keV. The soft X-rays are strongly absorbed (N(sub H) = 5 x 10(exp 22)/sq cm) suggesting a distance to GRS 1915+105 of the order of 8 kpc. Possible explanations of the source nature are discussed together with the peculiar light curve at hard X-rays.

Greiner, J.↗
NASA NTRS2010

The Latest Space-Borne Observations of TGFs from Fermi-GBM

The Gamma-ray Burst Monitor (GBM) on the Fermi Gamma-ray Space Telescope Observatory (Fermi) is detecting about two TGFs per week. This rate has increased by a factor of approx.eight since launch when flight software was uploaded to the spacecraft in November 2009 in order to increase the sensitivity of GBM to TGFs. Weaker, un-triggered TGFs are now also being observed about once per day over selected low-latitude regions Americas. The high efficiency and time resolution (2 s) of GBM allows temporal features to be resolved so that some insight may be gained on the origin and transport of the gamma-ray photons through the atmosphere. TGFs are observed to be shorter than previously thought, with an average duration of approx.100 micro-s. The absolute times of TGFs are known to approx.10 micro-s, allowing accurate correlations of TGFs with lightning networks and other lightning-related phenomena. The events are observed in the thick bismuth germanate (BGO) scintillation detectors of GBM with photon energies above 40 MeV. Other new results on the temporal and spectral characteristics of TGFs will be presented, along with properties of several electron-positron TGF events that have been identified.

Fishman, Gerald J.↗
NASA NTRS2010

Terrestrial Gamma-Ray Flashes (TGFs)

This slide presentation reviews the observation of Terrestrial Gamma Ray Flashes (TGFs) by Gamma-Ray Telescopes. These were: (1) BATSE /Compton Observatory, (2) Solar Spectroscopic Imager, (3) AGILE Gamma-ray Telescope, and (4) Gamma-ray Burst Monitor (GBM) on the Fermi Gamma-ray Space Telescope. It contains charts which display the counts over time, a map or the TGFs observed by the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI). and a map showing the latitude and longitude of 85 of the TGFs observed by the Fermi GBM.

Fishman, Gerald J.↗
NASA NTRS1981

Annihilation radiation from a hot e(+)-e(-) plasma

Pair annihilation in hot e(+)-e(-) plasmas is studied. The annihilation rate, luminosity and spectrum of optically thin plasmas of temperatures above 10 to the 8th power K are calculated by means of a Monte Carlo simulation. For a given temperature, the spectrum is peaked at an energy equal to 0.511 MeV plus a positive definite quantity of order kT. In high temperature sources, such as gamma ray bursts, this blue shift can amount to a significant fraction of 0.511 MeV. The annihilation line is also temperature broadened. The width varies as T to the 1/2 power for kT much less than 0.511 MeV, and as T for kT much greater than 0.511 MeV. The widths of the 400 to 460 keV emission lines observed from several gamma ray bursts set limits on the temperatures of the pair annihilation region in burst sources. The burst emission is either nonthermal or the pair annihilation region is spatially distinct from the site of the outburst itself.

Ramaty, R.↗
NASA NTRS2012

Three Decades of Magnetars

Magnetars are magnetically powered rotating neutron stars with extreme magnetic fields (over 10^14 Gauss). They were discovered in the X- and gamma-rays where they predominantly emit their radiation. Very few sources (roughly 24) have been found since their discovery in 1987. NASA's Fermi Gamma-ray Space Telescope was launched June 11, 2009; since then the Fermi Gamma-ray Burst Monitor (GBM) recorded emission from several magnetar sources. In total, six new sources were discovered between 2008 and 2011, with a synergy between Swift, RXTE, Fermi and the Interplanetary Network (IPN). In my talk I will give a short history of magnetars and describe how this, once relatively esoteric field, has emerged as a link between several astrophysical areas including Gamma-Ray Bursts. Finally, I will describe the exciting new results of Fermi and Chandra in this field and the current status of our knowledge of the magnetar population properties and magnetic fields.

Kouveliotou, C.↗