Engineering topics

Edwards, S.

Publications and source records attributed to Edwards, S..

7 records

DOE OSTI2025

Erratum: Centrality-Dependent Modification of Jet-Production Rates in Deuteron-Gold Collisions at $\sqrt{𝑠_{𝑁⁢𝑁}}$ = 200 GeV [Phys. Rev. Lett. 116, 122301 (2016)]

We previously reported jet-production rates in 𝑝 + 𝑝 and 𝑑 + Au collisions at $\sqrt{𝑠_{𝑁⁢𝑁}}$ = 200 GeV recorded in 2008 with the PHENIX detector at the Relativistic Heavy Ion Collider. Subsequently, we found that electronic noise in the electromagnetic calorimeter was not completely removed by the tower-timing cuts used in the analysis. We have conducted an independent re-analysis of the data that eliminated noisy towers by removing them completely from the analysis. These cuts remove any contributions from instrumental noise, but reduce the overall acceptance for electromagnetic clusters by ≈16% and hence the overall statistical power of the data. Finally, this re-analysis found that instrumental noise in the electromagnetic calorimeter led to an artificial increase in the jet yield for both the 𝑝 + 𝑝 and 𝑑 + Au collisions.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

NASA NTRS1997

Airfoil Design Using a Coupled Euler and Integral Boundary Layer Method with Adjoint Based Sensitivities

The objective of this paper is to present a control theory approach for the design of airfoils in the presence of viscous compressible flows. A coupled system of the integral boundary layer and the Euler equations is solved to provide rapid flow simulations. An adjunct approach consistent with the complete coupled state equations is employed to obtain the sensitivities needed to drive a numerical optimization algorithm. Design to target pressure distribution is demonstrated on an RAE 2822 airfoil at transonic speed.

Edwards, S.↗

NASA NTRS1993

Detection of circumstellar gas associated with GG Tauri

Double-peaked (C-12)O (1-0) emission centered on the young T Tauri star GG Tau possesses a line profile which may be modeled on the assumption that CO emission arises in an extended circumstellar disk. While bounds on the observed gas mass can be estimated on this basis, it is suggested that a large amount of mass could lie within a small and optically thick region, escaping detection due to beam-dilution effects. In addition, CO may no longer accurately trace the gas mass due to its dissociation, or freezing into grains, or due to the locking-up of carbon into more complex molecules.

Skrutskie, M. F.↗

NASA NTRS1989

Pre-main-sequence disk accretion in Z Canis Majoris

It is suggested that the pre-main-sequence object Z CMa is a luminous accretion disk, similar in many respects to the FU Orionis variables. Z CMa shows the broad, doubled optical absorption lines expected from a rapidly rotating accretion disk. The first overtone CO absorption detected in Z CMa is blue-shifted, suggesting line formation in a disk wind. Accretion at rates about 0.001 solar mass/yr over 100 yr is required to explain the luminosity of Z CMa. The large amount of material accreted (0.1 solar mass/yr) indicates that Z CMa is in a very early stage of stellar evolution, possibly in an initial phase of massive disk accretion.

Hartmann, L.↗

NASA NTRS1986

Extended far-infrared emission associated with mass outflows from young stars: L1551 IRS 5

Coadded IRAS survey data have been examined in the L1551 region. Extended low-surface-brightness 60 and 1200-micron emission is aligned with the molecular outflow from L1551 IRS 5. The morphology and the uniform surface brightness and color temperature of the IR emission suggest that the wind from IRS 5 is the source of this emission. It is suggested that radiative heating of grains by photons generated at the stellar wind/cloud interface is a major contributor to the extended infrared emission.

Edwards, S.↗

NASA NTRS1984

Brackett-alpha line profiles of young stellar objects

Profiles of the Br-alpha line of H I at a velocity resolution of 45 km/s are presented for the compact imbedded infrared objects BN, S106/IRS 3, GLS 490, GL 961, GL 989, Mon. R2/IRS 2, and for the visible objects LkH-alpha 101, T Tau, and R Mon. A proportionality obtained between Br-alpha luminosity and bolometric luminosity is shown to extend over three orders of magnitude, supporting the idea that the physical conditions and gas motions in the circumstellar envelopes of stellar objects are closely related over a wide range of luminosities. The Br-alpha line strengths are compared to radio continuum flux densities in the context of stellar wind models. Momentum deposition rates deduced from Br-alpha or radio continuum fluxes are consistent with those available in the radiation fields, which appear capable of driving the ionized gas outflows in the vicinity of the core sources. The results of a comparison of the H-alpha and Br-alpha profiles for T Tau are discussed.

Persson, S. E.↗

NASA NTRS1982

Wave-driven winds from cool stars. II - Models for T Tauri stars

The Alfven wave-driven wind theory of Hartmann and MacGregor is applied to T Tauri variables, including modifications which permit the calculation of wind temperatures. It is shown that large wave fluxes generate low-temperature winds, which can radiate strongly in Balmer and other optical emission lines. If wave fluxes are restricted to be less than the stellar luminosity, mass loss rates are restricted to values less than or equal to 10 to the -8th solar mass per year. Although these mass loss rates are low in comparison to many previous estimates, it is shown that the wind models produce optical and ultraviolet emission roughly consistent with observations. The theory predicts large wave amplitudes, so that 'turbulent' velocities are generally comparable to, or larger than, local expansion velocities in the optical line-emitting regions, thus making the Sobolev approximation invalid. It is suggested that the discrepancy between the mass loss rates predicted here and previously estimated values is due to the inapplicability of the Sobolev approximation in T Tauri winds.

Hartmann, L.↗