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All sourcesNASA NTRSDOE OSTI
NASA NTRS2002

A Measurement of the Non-Thermal X-Ray Emission of the Supernova Remnant RX J1713.7-3946

The ALP grant was used to support our analysis of the RXTE, ASCA, and ROSAT data for the supernova remnant RX J 1713.7-3946 and to publicize the results of the analysis. This remnant is one of only two whose X-ray emission is dominated by non-thermal emission and that have been detected at Texas energies. Previous X-ray studies failed to find evidence of thermal X-ray emission. For the first time, we have found such evidence for emission from the center of the remnant. The results of our analysis indicate that the average density of the material into which the remnant has expanded is very low. The lack of evidence of thermal emission from the bright northwestern rim of the remnant places an extremely strong constraint on the amount of Texas emission that can be produced by the interaction of very-high energy cosmic-ray protons accelerated in the remnant with other protons in the remnant. This constraint is inconsistent with the published claim that the Texas emission from the rim is due to the decay of neutral plans produced by the collision of Texas protons with material in the remnant. We offer an alternative interpretation of the gamma-ray data which is consistent with all of the available data: the gamma-ray emission is produced by inverse Compton emission from very-high energy electrons. In summary the grant has helped us solve two mysteries about the remnant. The results of this analysis will be published soon in the Astrophysical Journal.

Source record↗
DOE OSTI2023

Measurement of the CKM angle γ with B ± → D[K ∓ π ± π ± π ∓ ]h ± decays using a binned phase-space approach

The CKM angle γ is determined from CP-violating observables measured in B ± → D[K ∓ π ± π ± π ∓ ]h ± , (h = K, π) decays, where the measurements are performed in bins of the decay phase-space of the D meson. Using proton-proton collision data collected by the LHCb experiment at centre-of-mass energies of 7, 8 and 13 TeV, corresponding to a total integrated luminosity of 9 fb –1 , γ is determined to be $\gamma ={\left(54.8\begin{array}{c}+6.0\\ {}-5.8\end{array}\begin{array}{c}+0.6\\ {}-0.6\end{array}\begin{array}{c}+6.7\\ {}-4.3\end{array}\right)}^{\circ },$ where the first uncertainty is statistical, the second systematic and the third from the external inputs on the coherence factors and strong phases of the D-meson decays.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
NASA NTRS1975

Time-dependent 2.2 MeV and 0.5 MeV lines from solar flares

The time dependences of the 2.2 MeV and 0.51 MeV gamma ray lines from solar flares are calculated and the results are compared with observations of the 1972, August 4 and 7 flares. Time lag between the nuclear reactions and the formation of these two lines are caused, respectively, by capture of the neutrons, and by deceleration of the positrons and decay of the radioactive nuclei. Results show that the calculation is consistent with the observed rise of the 2.2 MeV line on August 4, and it does not require different time dependences for the accelerated protons and electrons in the flare region. The above lags can explain the delayed gamma ray emission observed on August 7. Positrons of energies greater than about 10 MeV could be detected in interplanetary space following large solar flares.

Wang, H. T.↗
NASA NTRS1988

Supernova 1987A

Supernova 1987A (February 23, 1987) in the Large Magellanic Cloud is the brightest supernova to be observed since SN 1604 AD (Kepler). Detection of a burst of neutrinos indicates that a neutron star was formed. Radioactive decay of about 0.07 solar mass of Co-56 is responsible for the observed optical light as well as hard X-rays and gamma-ray lines. Ultraviolet, optical, and infrared 'light echoes' and soft X-rays provide information on the distribution of circumstellar matter and the evolution of the progenitor star.

Mccray, Richard↗
DOE OSTI2026

Evidence for an isomeric {pi}½{sup +}[411] state in {sup 183}Ta

We report on the identification of a new isomeric state in Ta populated via the ground-state -decay of Hf. The experiment was performed at the KISS setup at RIKEN, where neutron-rich hafnium isotopes were produced via multi-nucleon transfer (MNT) reactions, followed by laser ionization of hafnium atoms, mass separation, and detection using an electron-gamma coincidence system. Isomeric spectroscopy was carried out by gating on different electron-gamma time correlations. A 459.1 keV -ray transition was identified in delayed spectra, and a half-life of μ was extracted through time-distribution fitting. The 459.1 keV state in Ta is known from previous work and has been assigned a Nilsson orbital configuration of , while a proposed new isomeric state above it is interpreted as a configuration that decays to via a low-energy, unobserved E2 transition. This is consistent with the systematic trends in neighbouring odd-A nuclei and transition rate calculations. Similar content being viewed by others

Doshi, S.↗
DOE OSTI2024

Magnetic dipole γ-ray strength functions in the crossover from spherical to deformed neodymium isotopes

We calculate the magnetic dipole $\gamma$-ray strength functions in a chain of even-mass neodymium isotopes $^{144-152}$Nd in the framework of the configuration-interaction (CI) shell model. We infer the strength function by applying the maximum entropy method (MEM) to the exact imaginary-time response function calculated with the shell-model Monte Carlo (SMMC) method. The success of the MEM depends on the choice of a good strength function as a prior distribution. We investigate two choices for the prior strength function: the static path approximation (SPA) and the quasiparticle random-phase approximation (QRPA). We find that the QRPA is a better approximation at low temperatures (i.e., near the ground state), while the SPA is a better choice at finite temperatures. We identify a low-energy enhancement (LEE) in the MEM deexcitation $M1$ strength functions of the even-mass neodymium isotopes and compare with recent experimental results for the total deexcitation $\gamma$-ray strength functions. The LEE is already seen in the SPA strength function but not in the QRPA strength function, indicating the importance of large-amplitude static fluctuations around the mean field in reproducing the LEE. Our method is currently the only one which can reproduce LEE in heavy open-shell nuclei where conventional CI shell model calculations are prohibited. With the onset of deformation as number of neutrons increases along the chain of neodymium isotopes, we observe that some of the LEE strength transfers to a low-energy excitation, which we interpret as a finite-temperature ``scissors'' mode. Here, we also observe a finite-temperature spin-flip mode.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
NASA NTRS1973

Solar flare proton spectrum averaged over the last 5000 years

The solar flare differential energy spectrum and integral proton flux above 10 MeV averaged over the last several thousand years are derived from thermoluminescence (TL) data. The dose-rate depth profile is obtained using a new TL equilibrium technique which is independent of the TL decay kinetics. The dose-rate depth profile produced by solar flare protons with a differential energy spectrum of the form dJ/dE = KE to the minus gamma power is calculated for arbitrary gamma. The best fit to the TL data in rock 14310 is obtained for gamma = 2.3 plus or minus 0.2 and an omnidirectional (4 pi) integral flux above 10 MeV of 40 to 80 prot/sq cm/sec. The TL half-life is determined to be 2000 yr. These results are compared to those for Na-22 (half-life of. 2.6 yr) and Al-26 (half-life of 740,000 yr) obtained by Wahlen et al. (1972) and Rancitelli et al. (1972), and it is concluded that the spectral shape and flux of protons in the interval from 25 to 100 MeV is the same within experimental errors when averaged over these three very different time periods.

Hoyt, H. P., Jr.↗
NASA NTRS1988

Background events in microchannel plates

Measurements have been made to assess the characteristics and origins of background events in microchannel plates (MCPs). An overall background rate of about 0.4 events/sq cm persec has been achieved consistently for MCPs that have been baked and scrubbed. The temperature and gain of the MCPs are found to have no significant effect on the background rate. Detection of 1.46-MeV gamma rays from the MCP glass confirms the presence of K-40, with a concentration of 0.0007 percent, in MCP glass. It is shown that beta decay from K-40 is sufficient to cause the background rate and spectrum observed. Anticoincidence measurements indicate the the background rate caused by cosmic ray interactions is small (less than 0.016 events/sq cm per sec).

Siegmund, O. H. W.↗
NASA NTRS2003

Stochastic Mixing Model with Power Law Decay of Variance

Here we present a simple stochastic mixing model based on the law of large numbers (LLN). The reason why the LLN is involved in our formulation of the mixing problem is that the random conserved scalar c = c(t,x(t)) appears to behave as a sample mean. It converges to the mean value mu, while the variance sigma(sup 2)(sub c) (t) decays approximately as t(exp -1). Since the variance of the scalar decays faster than a sample mean (typically is greater than unity), we will introduce some non-linear modifications into the corresponding pdf-equation. The main idea is to develop a robust model which is independent from restrictive assumptions about the shape of the pdf. The remainder of this paper is organized as follows. In Section 2 we derive the integral equation from a stochastic difference equation describing the evolution of the pdf of a passive scalar in time. The stochastic difference equation introduces an exchange rate gamma(sub n) which we model in a first step as a deterministic function. In a second step, we generalize gamma(sub n) as a stochastic variable taking fluctuations in the inhomogeneous environment into account. In Section 3 we solve the non-linear integral equation numerically and analyze the influence of the different parameters on the decay rate. The paper finishes with a conclusion.

Fedotov, S.↗
NASA NTRS1975

Time-dependent 2.2-MeV and 0.5-MeV lines from solar flares

The time dependences of the 2.2- and 0.51-MeV gamma-ray lines from solar flares are calculated, and the results are compared with observations of the 1972 August 4 and 7 flares. The time lag between the nuclear reactions and the formation of these two lines is caused by capture of the neutrons and subsequent deceleration of the positrons and decay of the radioactive nuclei. Our main results are that the calculation is consistent with the observed rise of the 2.2-MeV line on August 4, and it does not require different time dependences for the accelerated protons and high-energy electrons in the flare region. The above lags can explain the delayed gamma-ray emission observed on August 7. Positrons of energies greater than about 10 MeV could be detected in interplanetary space following large solar flares.

Wang, H. T.↗
NASA NTRS1983

H0547-14 - X-ray flux from a weak gamma-ray burst?

Data concerning a fast X ray transient observed by the HEAO 1 on March 17, 1978 are discussed. The object, labeled H0547-14, was located in Lepus, with galactic coordinates 219.37 deg longitude, b = -20.12 deg in the anticenter direction. A 10 sec scan of the transient was obtained with proportional counter detectors. An X ray luminosity of more than 5.1 x 10 to the 31st ergs/sec was measured as a lower limit, with the decay taking 17 min. A lower limit to the flare was set at 30 sec. The flux intensity resided in the range 4.4/1 billion-4/100 million erg/sq cm per sec, with a rise time of a factor of 10 in about 5 sec. Possible characterizations of the object, as either a gamma ray burst or as an M dwarf star, are discussed.

Ambruster, C.↗
NASA NTRS2011

The 2010 Very High Energy Gamma-Ray Flare and 10 Years of Multi-Wavelength Observations of M87

The giant radio galaxy M87 with its proximity (16 Mpc), famous jet, and very massive black hole ((3-6) X 10(exp 9) Solar Mass) provides a unique opportunity to investigate the origin of very high energy (VHE; E>100 GeV) gamma-ray emission generated in relativistic outflows and the surroundings of super-massive black holes. M87 has been established as a VHE gamma -ray emitter since 2006. The VHE gamma -ray emission displays strong variability on timescales as short as a day. In this paper, results from a joint VHE monitoring campaign on M87 by the MAGIC and VERITAS instruments in 2010 are reported. During the campaign, a flare at VHE was detected. triggering further observations at VHE (H.E.S.S.), X-rays (Chandra), and radio (43 GHz VLBA). The excellent sampling of the VHE gamma-ray light curve enables one to derive a precise temporal characterization of the flare: the single, isolated flare is well described by a two-sided exponential function with significantly different flux rise and decay times of rise tau ((sup rise sub d) = (1:69 +/- 0:30) days and tau(sup decay sub d = (0:611 +/- 0:080) days, respectively. While the overall variability pattern of the 2010 flare appears somewhat different from that of previous VHE flares in 2005 and 2008, they share very similar timescales (approx day), peak fluxes (Phi (sub > 0:35 TeV) approx. equals (1 - 3) X 10(exp -11) ph / square cm/s), and VHE spectra. 43 GHz VLBA radio observations of the inner jet regions indicate no enhanced flux in 2010 in contrast to observations in 2008, where an increase of the radio flux of the innermost core regions coincided with a VHE flare. On the other hand, Chandra X-ray observations taken approx 3 days after the peak of the VHE gamma -ray emission reveal an enhanced flux from the core (flux increased by factor approx 2; variability timescale < 2 days). The long-term (2001-2010) multi-wavelength (MWL) light curve of M87, spanning from radio to VHE and including data from HST, LT, VLA and EVN, is used to further investigate the origin of the VHE gamma -ray emission. No unique, common MWL signature of the three VHE flares has been identified. In the outer kpc jet region, in particular in HST-1, no enhanced MWL activity was detected in 2008 and 2010, disfavoring it as the origin of the VHE flares during these years. Shortly after two of the three flares (2008 and 2010), the X-ray core was observed to be at a higher flux level than its characteristic range (determined from more than 60 monitoring observations: 2002-2009). In 2005, the strong flux dominance of HST-1 could have suppressed the detection of such a feature. Published models for VHE gamma -ray emission from M87 are reviewed in the light of the new data.

Abramowski, A.↗
DOE OSTI2021

Nuclear Data Sheets for A=214

Here, experimental nuclear structure and decay data are evaluated for all of 12 known nuclides of mass 214 (Hg, Tl, Pb, Bi, Po, At, Rn, Fr, Ra, Ac, Th, Pa). For each nuclide, detailed evaluated spectroscopic information is presented in each reaction and decay, and the best values combining all available data are recommended for level properties, γ and β radiations, and other spectroscopic properties in the Adopted Levels and Gammas. The present evaluation supersedes the earlier one on A=214 by S.-C. Wu (2009Wu02), published in Nuclear Data Sheets 110, 681 (2009).

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2022

Nuclear Data Sheets for A=236

Experimental nuclear structure and decay data are evaluated for all of 10 known nuclides of mass 236 (Ac, Th, Pa, U, Np, Pu, Am, Cm, Bk, Cf). For each nuclide, detailed evaluated spectroscopic information is presented in each reaction and decay, and the best values combining all available data are recommended for level properties, γ and β radiations, and other spectroscopic properties in the Adopted Levels and Gammas. The present evaluation supersedes the earlier one on A=236 by E. Browne, J. K. Tuli (2006Br20), published in Nuclear Data Sheets 107, 2641 (2006).

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
NASA NTRS2012

GRB 120422A: a Low-Luminosity Gamma-Ray Burst Driven by a Central Engine

GRB 120422A is a low-luminosity gamma-ray burst (GRB) associated with a bright supernova, which distinguishesitself by its relatively short T(sub 90) (approximately 5 s) and an energetic and steep-decaying X-ray tail. We analyze the Swift BurstAlert Telescope and X-ray Telescope data and discuss the physical implications. We show that the steep declineearly in the X-ray light curve can be interpreted as the curvature tail of a late emission episode around 58-86 s,with a curved instantaneous spectrum at the end of the emission episode. Together with the main activity in thefirst 20 s and the weak emission from 40 s to 60 s, the prompt emission is variable, which points to a centralengine origin in contrast to a shock-breakout origin, which is used to interpret some other nearby low-luminosity supernova GRBs. Both the curvature effect model and interpreting the early shallow decay as the coasting externalforward shock emission in a wind medium provide a constraint on the bulk Lorentz factor to be around several.Comparing the properties ofGRB 120422A and other supernova GRBs,we find that themain criterion to distinguish engine-driven GRBs from shock-breakout GRBs is the time-averaged -ray luminosity. Engine-driven GRBs likelyhave a luminosity above approximately 10(sup 48) erg s(sup -1).

engine↗
NASA NTRS2004

GRB 021211 as a Faint Analogue of GRB 990123: Exploring the Similarities and Differences in the Optical Afterglows

We present BVR(sub c)JHK(sub s) photometry of the optical afterglow of the gamma-ray burst GRB 021211 taken at the Magellan, MMT, and WIYN observatories between 0.7 and 50 days after the burst. We find an intrinsic spectral slope at optical and near-infrared wavelengths of 0.69 +/- 0.14 at 0.87 days. The optical decay during the first day is almost identical to that of GRB 990123 except that GRB 021211's optical afterglow was intrinsically approximately 38 times fainter and the transition from the reverse shock to the forward shock may have occurred earlier than it did for GRB 990123. We find no evidence for a jet break or the cooling break passing through optical frequencies during the first day after the burst. There is weak evidence for a break in the J-band decay between 0.89 and 1.87 days which may be due to a jet. The optical and infrared data are consistent with a relativistic fireball where the shocked electrons are in the slow cooling regime and the electron index is 2.3 +/- 0.1. The burst appears to have occurred in a homogeneous ambient medium. Our analysis suggests that the jet of GRB 021211 may have a small opening angle (1.4 deg-4.4 deg) and that the total gamma-ray energy is much less than the canonical value of 1.33 x 10(exp 51) erg. If, this is the case then most of the energy of the burst may be in another form such as a frozen magnetic field, in supernova ejecta, or in a second jet component. The host galaxy of GRB 021211 is subluminous and has a star formation rate of at least 1 solar mass/yr.

Holland, Stephen T.↗
NASA NTRS2021

INTEGRAL reloaded: Spacecraft, instruments and ground system

The European Space Agency’s INTErnational Gamma-Ray Astrophysics Laboratory (ESA/INTEGRAL) was launched aboard a Proton-DM2 rocket on 17 October 2002 at 06:41 CEST, from Baikonur in Kazakhstan. Since then, INTEGRAL has been providing long, uninterrupted observations (up to about 47 h, or 170 ksec, per satellite orbit of 2.7 days) with a large field-of-view (FOV, fully coded: 100 deg), millisecond time resolution, keV energy resolution, polarization measurements, as well as additional wavelength coverage at optical wavelengths. This is realized by two main instruments in the 15 keV to 10 MeV energy range, the spectrometer SPI (spectral resolution 3 keV at 1.8 MeV) and the imager IBIS (angular resolution: 12 arcmin FWHM), complemented by X-ray (JEM-X; 3–35 keV) and optical (OMC; Johnson V-band) monitor instruments. All instruments are co-aligned to simultaneously observe the target region. A particle radiation monitor (IREM) measures charged particle fluxes near the spacecraft. The Anti-coincidence subsystems of the main instruments, built to reduce the background, are also very efficient all-sky γ-ray detectors, which provide virtually omni-directional monitoring above ~75 keV. Besides the long, scheduled observations, INTEGRAL can rapidly (within a couple of hours) re-point and conduct Target of Opportunity (ToO) observations on a large variety of sources. INTEGRAL observations and their scientific results have been building an impressive legacy: The discovery of currently more than 600 new high-energy sources; the first-ever direct detection of (56)Ni and (56)Co radio-active decay lines from a Type Ia supernova; spectroscopy of isotopes from galactic nucleo-synthesis sources; new insights on enigmatic positron annihilation in the Galactic bulge and disk; and pioneering gamma-ray polarization studies. INTEGRAL is also a successful actor in the new multi-messenger astronomy introduced by non-electromagnetic signals from gravitational waves and from neutrinos: INTEGRAL found the first prompt electromagnetic radiation in coincidence with a binary neutron star merger. Up to now more than 1750 scientific papers based on INTEGRAL data have been published in refereed journals. In this paper, we will give a comprehensive update of the satellite status after more than 18 years of operations in a harsh space environment, and an account of the successful Ground Segment.

Erik Kuulkers↗
NASA NTRS1976

Formation of the 0.511.-MeV line in solar flares

The gamma-ray line produced at 0.51-MeV was studied and is shown to be the result of either of free annihilation of positrons with electrons or of the decay of positronium by 2-photon emission. Positron annihilation from the bound state of positronium may also proceed by 3-photon emission, resulting in a continuum with energies up to 0.51-MeV. Accurate calculations of the rates of free annihilation and positronium formation in a solar-flare plasma are presented. Estimates of the positronium-formulation rates by charge exchange and the rates of dissociation and quenching are also considered. The temperature and density dependence of the ratio of 3-photon to 2-photon emission was obtained. It is shown that when the ratio of free electrons to neutral atoms in the plasma is approximately unity or greater, the Doppler width of the 0.51-MeV line is a function of the temperature of the annihilation region. For the small ion densities characteristics of the photosphere, the width is predominantly a function of the density.

Crannell, C. J.↗