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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 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1998

X-Ray Emission from the Unidentified Gamma Ray Transient GRO J1838-0415 and X-Ray Localization of Gamma-Ray Transients near the Galactic Plane

The investigation was focused on studying the residual X-ray emission from possible counterparts of enigmatic gamma-ray transients near the Galactic plane. These sources (discovered by our group at Columbia) are highly variable gamma-ray sources with no radio-loud spectrally flat blazar in their approx 1 deg. diameter error box. BSAX Narrow Field Instruments pointed the gamma-ray error box of the prominent non-blazar Energetic Gamma Ray Experiment Telescope (EGRET) source GRO 1838-04 twice on April 17, 1997, and on April 20, 1997. Most of the EGRET error box was imaged and several faint X-ray sources were detected. BSAX Wide Field Camera data were also obtained for a variety of sources near the Galactic plane, including GRO J1838-04.

Tavani, Marco↗
NASA NTRS2013

X-ray Follow-ups of XSS J12270-4859: A Low-mass X-ray Binary with Gamma-ray Fermi-LAT Association

Context. XSS J1227.0-4859 is a peculiar, hard X-ray source recently positionally associated to the Fermi-LAT source 1FGL J1227.9- 4852/2FGL J1227.7-4853. Multi-wavelength observations have added information on this source, indicating a low-luminosity lowmass X-ray binary (LMXB), but its nature is still unclear. Aims. To progress in our understanding, we present new X-ray data from a monitoring campaign performed in 2011 with the XMM-Newton, RXTE, and Swift satellites and combine them with new gamma-ray data from the Fermi and AGILE satellites. We complement the study with simultaneous near-UV photometry from XMM-Newton and with previous UV/optical and near-IR data. Methods. We analysed the temporal characteristics in the X-rays, near-UV, and gamma rays and studied the broad-band spectral energy distribution from radio to gamma rays. Results. The X-ray history of XSS J1227 over 7 yr shows a persistent and rather stable low-luminosity (6 × 1033 d2 1 kpcerg s−1) source, with flares and dips being peculiar and permanent characteristics. The associated Fermi-LAT source 2FGL J1227.7-4853 is also stable over an overlapping period of 4.7 yr. Searches for X-ray fast pulsations down to msec give upper limits to pulse fractional amplitudes of 15−25% that do not rule out a fast spinning pulsar. The combined UV/optical/near-IR spectrum reveals a hot component at approximately 13 kK and a cool one at approximately 4.6 kK. The latter would suggest a late-type K2−K5 companion star, a distance range of 1.4−3.6 kpc, and an orbital period of 7-9 h. A near-UV variability (6 h) also suggests a longer orbital period than previously estimated. Conclusions. The analysis shows that the X-ray and UV/optical/near-IR emissions are more compatible with an accretion-powered compact object than with a rotational powered pulsar. The X-ray to UV bolometric luminosity ratio could be consistent with a binary hosting a neutron star, but the uncertainties in the radio data may also allow an LMXB black hole with a compact jet. In this case, it would be the first associated with a high-energy gamma-ray source.

deMartino, D.↗
NASA NTRS1973

Cosmic-ray exposure history of North Ray and South Ray material

Cosmic-ray exposure ages for two breccias, 68815 and 69935, in the vicinity of South Ray Crater give consistent values of 2.0 plus or minus 0.2 m.y. when measured by the Kr-81-Kr, Na-22-Ne, and particle track methods. These also agree with estimates of exposure ages made by others using microcrater counts on six rocks in the same vicinity, including 69935. It is likely that this represents the age of South Ray Crater. Soils from stations close to South Ray Crater appear to be mature, well-irradiated materials containing little, if any, of a 2 m.y. component. Reviewing various lines of evidence, it is concluded that there are no compelling reasons to believe that so-called South Ray soils contain a large fraction of South Ray ejecta. However, if they do contain such ejecta, this material must have been well irradiated in situ prior to being thrown out in the South Ray event. A chip from a large boulder on the rim of North Ray Crater gives a Kr-81-Kr age of 50.6 plus or minus 3.8 m.y. Similar ages are found by the Na-22-Ne and the particle track methods. The agreement of this result with other data on large North Ray boulders fixes the age of North Ray Crater as 50 m.y.

Behrmann, C.↗
NASA NTRS1994

First Year PIDDP Report on gamma-ray and x-ray spectroscopy: X-ray remote sensing and in situ spectroscopy for planetary exploration missions and gamma-ray remote sensing and in situ spectroscopy for planetary exploration missions

Detectors that will be used for planetary missions must have their responses calibrated in a reproducible manner. In addition, it is important to characterize a detector system at uneven portions of its life cycle, for example after exposure to different amounts of radiation. A calibration and response characterization facility has been constructed at Schlumberger-Doll Research for all types of gamma- and x-ray detectors that may be used for planetary measurement. This facility is currently being tested. Initial use is expected for the MARS 94 detectors. The facility will then also be available for calibrating other detectors as well as arrays of detectors such as the NEAR detector with its central Nal(TI) crystal surrounded with a large BGO crystal. Cadmium telluride detectors are investigated for applications in space explorations. These detectors show an energy resolution of 5 keV for the 122 keV 57Co line. Earlier reported polarization effects are not observed. The detectors can be used at temperatures up to 100 C, although with reduced energy resolution. The thickness of standard detectors is limited to 2 mm. These detectors become fully efficient at bias voltages above 200 V. Initial results for a 1 cm thick detector show that the quality of the material is inferior to the thinner standard detectors and hole trapping affects the pulse height. A detailed characterization of the detector is in progress. Prototypes of photomultipliers based on a Channel Electron Multiplier (CEM) are being built to study their performance. Such photomultipliers promise better timing characteristics and a higher dynamic range while being more compact and of lower in weight.

Mahdavi, M.↗
NASA NTRS2004

X-Ray and TeV Gamma-Ray Observations of the Strong TeV Gamma-Ray Blazars Mrk 501 and 1ES 1959+650

In June 2003, the blazar 1ES 1959+650 showed a very high level of X-ray activity. The 2-12 keV flux measured with the RXTE All Sky Monitor exceeded 10 mCrab for a prolonged time. We therefore invoked RXTE multiwavelength observations of the source. It was observed with RXTE between May 2,2003 and June 7,2003 with a total integration time of 33 ksec. We complemented the RXTE observations with TeV gamma- ray observations with the Whipple 10 m Cherenkov telescope (Mt. Hopkins, &.). In addition, we invoked radio observations with the UMRAO radio telescope (Aller et al.) and with the Bordeaux optical observatory (P. Charlot et al.). The RXTE observations revealed several X-ray flares with large amplitude variations of the 3 keV - 15 keV spectral index. While the X-ray flares were of intermediate amplitude - some of them comparable to the high X-ray fluxes measured in 2002 - the source remained unexpectedly quiet at TeV gamma-rays. The analysis of the Whipple 10 m TeV gamma-ray data did not result in a firm detection.

Krawczynski, Henric↗
NASA NTRS1999

"X-Ray Transients in Star-Forming Regions" and "Hard X-Ray Emission from X-Ray Bursters"

This grant funded work on the analysis of data obtained with the Burst and Transient Experiment (BATSE) on the Compton Gamma-Ray Observatory. The goal of the work was to search for hard x-ray transients in star forming regions using the all-sky hard x-ray monitoring capability of BATSE. Our initial work lead to the discovery of a hard x-ray transient, GRO J1849-03. Follow-up observations of this source made with the Wide Field Camera on BeppoSAX showed that the source should be identified with the previously known x-ray pulsar GS 1843-02 which itself is identified with the x-ray source X1845-024 originally discovered with the SAS-3 satellite. Our identification of the source and measurement of the outburst recurrence time, lead to the identification of the source as a Be/X-ray binary with a spin period of 94.8 s and an orbital period of 241 days. The funding was used primarily for partial salary and travel support for John Tomsick, then a graduate student at Columbia University. John Tomsick, now Dr. Tomsick, received his Ph.D. from Columbia University in July 1999, based partially on results obtained under this investigation. He is now a postdoctoral research scientist at the University of California, San Diego.

Halpern, Jules P.↗
NASA NTRS1985

X-ray emission from cataclysmic variables with accretion disks. I - Hard X-rays. II - EUV/soft X-ray radiation

Theoretical models explaining the hard-X-ray, soft-X-ray, and EUV emission of accretion-disk cataclysmic variables in terms of the disk boundary layer (DBL) are developed on the basis of a survey of the published observational data. The data are compared with model predictions in graphs for systems with high or low (greater than or less than 10-Pg/s) accretion rates. Good agreement is obtained both at low accretion rates, where an optically thin rarefied hot (Te = 10 to the 8th K) DBL radiates most of its energy as hard X-rays, and at high accretion rates, where an optically thick 100,000-K DBL radiates most of its energy in the EUV and as soft X-rays. Detailed analysis of the old nova V603 Aql suggests that previous models predicting more detections of soft-X-ray/EUV emissions from thick-DBL objects (Ferland et al., 1982) used inappropriate dwarf masses, interstellar column densities, or classical-nova space densities.

Patterson, J.↗
NASA NTRS1997

X-rays and gamma-rays from accretion flows onto black holes in Seyferts and X-ray binaries

Observations and theoretical models of X-ray/gamma ray spectra of radio quiet Seyfert galaxies and Galactic black hole candidates are reviewed. The spectra from these objects share the following characteristics: an underlying power law with a high energy cutoff above 200 keV; a Compton reflection component with a Fe K alpha line, and a low energy absorption by intervening cold matter. The X-ray energy spectral index, alpha, is typically in the range between 0.8 and 1 in Seyfert spectra, and that of the hard state spectra of the black hole candidates Cygnus X-1 and GX 339-4 is typically between 0.6 and 0.8. The Compton reflection component corresponds with cold matter covering a solid angle of between 0.8pi and 2pi as seen from the X-ray source. The broadband spectra of both classes of sources are well fitted by Compton upscattering of soft photons in thermal plasma. The fits yield a thermal plasma temperature of 100 keV and the Thomson optical depth of 1. All the spectra presented are cut off before the electron rest energy 511 keV, indicating that electron/positron pair production is an important process.

Zdziarski, Andrzej A.↗
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 NTRS1975

Relation of large-scale coronal X-ray structure and cosmic rays. I - Sources of solar wind streams as defined by X-ray emission and H-alpha absorption features

The large-scale structure of the corona and the interplanetary medium during Carrington rotations 1601-1607 is discussed relative to recurrent high-speed solar wind streams and their coronal sources. Only streams A, C, D, and F recur on more than one rotation. Streams A and D are associated with coronal holes, while C and F originate in the high corona (20-50 solar radii) over faint X-ray emissions. The association of the streams with holes is confirmed by earlier findings that there are no large equatorial holes without an associated high-speed stream and that the area of the equatorial region of coronal holes is highly correlated with the maximum velocity observed in the associated stream near 1 AU.

Krieger, A. S.↗
NASA NTRS1991

New constraints on neutron star models of gamma-ray bursts. II - X-ray observations of three gamma-ray burst error boxes

Exosat observations are presented for 3 gamma-ray-burst error boxes, one of which may be associated with an optical flash. No point sources were detected at the 3-sigma level. A comparison with Einstein data (Pizzichini et al., 1986) is made for the March 5b, 1979 source. The data are interpreted in the framework of neutron star models and derive upper limits for the neutron star surface temperatures, accretion rates, and surface densities of an accretion disk. Apart from the March 5b, 1979 source, consistency is found with each model.

Boer, M.↗
NASA NTRS1994

X-ray and gamma ray astronomy detectors

X-ray and gamma ray astronomy was made possible by the advent of space flight. Discovery and early observations of celestial x-rays and gamma rays, dating back almost 40 years, were first done with high altitude rockets, followed by Earth-orbiting satellites> once it became possible to carry detectors above the Earth's atmosphere, a new view of the universe in the high-energy part of the electromagnetic spectrum evolved. Many of the detector concepts used for x-ray and gamma ray astronomy were derived from radiation measuring instruments used in atomic physics, nuclear physics, and other fields. However, these instruments, when used in x-ray and gamma ray astronomy, have to meet unique and demanding requirements related to their operation in space and the need to detect and measure extremely weak radiation fluxes from celestial x-ray and gamma ray sources. Their design for x-ray and gamma ray astronomy has, therefore, become a rather specialized and rapidly advancing field in which improved sensitivity, higher energy and spatial resolution, wider spectral coverage, and enhanced imaging capabilities are all sought. This text is intended as an introduction to x-ray and gamma ray astronomy instruments. It provides an overview of detector design and technology and is aimed at scientists, engineers, and technical personnel and managers associated with this field. The discussion is limited to basic principles and design concepts and provides examples of applications in past, present, and future space flight missions.

Decher, Rudolf↗
NASA NTRS1995

Implications of Gamma-Ray Transparency Constraints in Blazars: Minimum Distances and Gamma-Ray Collimation

We develop a general expression for the gamma - gamma absorption coefficient, alpha(sub gamma(gamma)) for gamma-rays propagating in an arbitrary direction at an arbitrary point in space above an X-ray-emitting accretion disk. The X-ray intensity is assumed to vary as a power law in energy and radius between the outer disk radius, R(sub 0), and the inner radius, R(sub ms) which is the radius of marginal stability for a Schwarzschild black hole. We use our result for alpha(sub gamma(gamma)) to calculate the gamma - gamma optical depth, tau(sub gamma(gamma)) for gamma - rays created at height z and propagating at angle Phi relative to the disk axis, and we show that for Phi = 0 and z greater than or approx equal to R(sub 0), tau(sub gamma(gamma)) proportional to Epsilon(sup alpha)z(sup -2(alpha) - 3), where alpha is the X-ray spectral index and Epsilon is the gamma - ray energy. As an application, we use our formalism to compute the minimum distance between the central black hole and the site of production of the gamma-rays detected by EGRET during the 1991 June flare of 3C 279. In order to obtain an upper limit, we assume that all of the X-rays observed contemporaneously by Ginga were emitted by the disk. Our results suggest that the observed gamma - rays may have originated within less than or approx equal to 45 GM/sq c from a black hole of mass greater than or approx equal to 10(exp 9) solar mass, perhaps in active plasma located above the central funnel of the accretion disk. This raises the possibility of establishing a direct connection between the production of the observed gamma - rays and the accretion of material onto the black hole. We also consider the variation of the optical depth as a function of the angle of propagation Phi. Our results indicate that the "focusing" of the gamma - rays along the disk axis due to pair production is strong enough to explain the observed degree of alignment in blazar sources. If the gamma - rays are produced isotropically in gamma - ray blazars, then these objects should appear as bright MeV sources when viewed along off-axis lines of sight.

Becker, Peter A.↗
NASA NTRS1998

Monitoring X-Ray Emission from X-Ray Bursters

The goal of this investigation was to use the All-Sky Monitor on the Rossi X-Ray Timing Explorer (RXTE) in combination with the Burst and Transient Source Experiment on the Compton Gamma-Ray Observatory to simultaneously measure the x-ray (2-12 keV) and hard x-ray (20-100 keV) emission from x-ray bursters. The investigation was successful. We made the first simultaneous measurement of hard and soft x-ray emission and found a strong anticorrelation of hard and soft x-ray emission from the X-Ray Burster 4U 0614+091. The monitoring performed under this investigation was also important in triggering target of opportunity observations of x-ray bursters made under the investigation hard x-ray emission of x-ray bursters approved for RXTE cycles 1 and 2. These observations lead to a number of papers on high-frequency quasi-periodic oscillations and on hard x-ray emission from the x-ray bursters 4U 0614+091 and 4U 1705-44.

Kaaret, Philip↗
NASA NTRS2023

The High Energy X-Ray Probe (HEX-P): Galactic PeVatrons, Star Clusters, Superbubbles, Microquasar Jets, and Gamma-Ray Binaries

HEX-P is a probe-class mission concept that will combine high spatial resolution X-ray imaging (<10"FWHM) and broad spectral coverage (0.2--80 keV) with an effective area far superior to current facilities (including XMM-Newton and NuSTAR) to enable revolutionary new insights into a variety of important astrophysical problems. With the recent discoveries of over 40 ultra-high-energy gamma-ray sources (detected above 100 TeV) and neutrino emission in the Galactic Plane, we have entered a new era of multi-messenger astrophysics facing the exciting reality of Galactic PeVatrons. In the next decade, as more Galactic PeVatrons and TeV gamma-ray sources are expected to be discovered, the identification of their acceleration and emission mechanisms will be the most pressing issue in both particle and high-energy astrophysics. In this paper, along with its companion papers (Reynolds et al. 2023, Mori et al. 2023), we will present that HEX-P is uniquely suited to address important problems in various cosmic-ray accelerators, including Galactic PeVatrons, through investigating synchrotron X-ray emission of TeV--PeV electrons produced by both leptonic and hadronic processes. For Galactic PeVatron candidates and other TeV gamma-ray sources, HEX-P can fill in a large gap in the spectral-energy distributions (SEDs) of many objects observed in radio, soft X-rays, and gamma rays, constraining the maximum energies to which electrons can be accelerated, with implications for the nature of the Galactic PeVatrons and their contributions to the spectrum of Galactic cosmic rays beyond the knee at $\sim3$ PeV. In particular, X-ray observation with HEX-P and TeV observation with CTA will provide the most powerful multi-messenger diagnostics to identify Galactic PeVatrons and explore a variety of astrophysical shock mechanisms. We present simulations of each class of Galactic TeV--PeV sources, demonstrating the power of both the imaging and spectral capabilities of HEX-P to advance our knowledge of Galactic cosmic-ray accelerators. In addition, we discuss HEX-P’s unique and complementary roles to upcoming gamma-ray and neutrino observatories in the 2030s.

particle accelerators↗