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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 559 records · Page 31
All sourcesNASA NTRSDOE OSTI
DOE OSTI2012

THE {gamma}-RAY EMISSION REGION IN THE FANAROFF-RILEY II RADIO GALAXY 3C 111

The broad-line radio galaxy 3C 111, characterized by a Fanaroff-Riley II (FRII) radio morphology, is one of the sources of the misaligned active galactic nucleus sample, consisting of radio galaxies and steep spectrum radio quasars, recently detected by the Fermi Large Area Telescope (LAT). Our analysis of the 24 month {gamma}-ray light curve shows that 3C 111 was only occasionally detected at high energies. It was bright at the end of 2008 and faint, below the Fermi-LAT sensitivity threshold, for the rest of the time. A multifrequency campaign of 3C 111, ongoing in the same period, revealed an increase of the millimeter, optical, and X-ray fluxes in 2008 September-November, interpreted by Chatterjee et al. as due to the passage of a superluminal knot through the jet core. The temporal coincidence of the millimeter-optical-X-ray outburst with the GeV activity suggests a cospatiality of the events, allowing, for the first time, the localization of the {gamma}-ray dissipative zone in an FRII jet. We argue that the GeV photons of 3C 111 are produced in a compact region confined within 0.1 pc and at a distance of about 0.3 pc from the black hole.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2017

Triple collinear emissions in parton showers

A framework to include triple collinear splitting functions into parton showers is presented, and the implementation of flavor-changing next-to-leading-order (NLO) splitting kernels is discussed as a first application. The correspondence between the Monte Carlo integration and the analytic computation of NLO DGLAP evolution kernels is made explicit for both timelike and spacelike parton evolution. Numerical simulation results are obtained with two independent implementations of the new algorithm, using the two independent event generation frameworks PYTHIA and SHERPA.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2013

Is {gamma}-Ray Emission from Novae Affected by Interference Effects in the {sup 18}F({ital p},{ital {alpha}}){sup 15}O Reaction?

The 18F(p, alpha)O-15 reaction rate is crucial for constraining model predictions of the gamma-ray observable radioisotope F-18 produced in novae. The determination of this rate is challenging due to particular features of the level scheme of the compound nucleus, Ne-19, which result in interference effects potentially playing a significant role. The dominant uncertainty in this rate arises from interference between J(pi) = 3/2(+) states near the proton threshold (S-p = 6.411 MeV) and a broad J(pi) = 3/2(+) state at 665 keVabove threshold. This unknown interference term results in up to a factor of 40 uncertainty in the astrophysical S-factor at nova temperatures. Here we report a new measurement of states in this energy region using the F-19(He-3, t)Ne-19 reaction. In stark contrast to previous assumptions we find at least 3 resonances between the proton threshold and E-cm = 50 keV, all with different angular distributions. None of these are consistent with J(pi) = 3/2(+) angular distributions. We find that the main uncertainty now arises from the unknown proton width of the 48 keV resonance, not from possible interference effects. Hydrodynamic nova model calculations performed indicate that this unknown width affects F-18 production by at least a factor of two in the model considered.

Laird, A. M.↗