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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 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

Angular Momentum Evolution of Young Stars in the nearby Scorpius–Centaurus OB Association

We report the results of a study of archival SuperWASP light curves for stars in Scorpius–Centaurus (Sco–Cen), the nearest OB association. We use SuperWASP time-series photometry to extract rotation periods for 189 candidate members of the Sco–Cen complex and verify that 162 of those are members of the classic Sco–Cen subgroups of Upper Scorpius (US), Upper Centaurus-Lupus (UCL), and Lower Centaurus-Crux (LCC). This study provides the first measurements of rotation periods explicitly for large samples of pre-main-sequence (pre-MS) stars spanning the UCL and LCC subgroups. Our final sample of 157 well-characterized pre-MS stars spans ages of ∼10–20 Myr, spectral types of ∼F3–M0, and masses of M ≃ 0.3–1.5 M{sub ⊙}{sup N}. For this sample, we find a distribution of stellar rotation periods with a median of P {sub rot} ≃ 2.4 days, an overall range of 0.2 < P {sub rot} < 8 days, and a fairly well-defined mass-dependent upper envelope of rotation periods. This distribution of periods is consistent with recently developed stellar angular momentum evolution models. These data are significant because they represent an undersampled age range and the number of measurable rotation periods is large compared to recent studies of other regions. We also search for new examples of eclipsing disk or ring systems analogous to 1SWASP J140747.93-394542.6 (J1407), but find none. Our survey yielded five eclipsing binaries, but only one appears to be physically associated with the Sco–Cen complex. V2394 Oph is a heavily reddened (A {sub V} ≃ 5 mag) massive contact binary in the LDN 1689 cloud whose Gaia astrometry is clearly consistent with kinematic membership with the Ophiuchus star-forming region.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1975

Ionospheric effects of X-ray source Scorpius XR-1

A simple two-ion model was employed to evaluate the ionospheric effects of various nocturnal ionization sources. The model was used to calculate the decay of the electron number density at 90 km with and without illumination by Scorpius XR-1 X rays. Reflection parameters for the determination of the effect of cosmic x-ray sources on radio wave propagation were also obtained. The results obtained in the investigation do not support the proposal made by Anathakrishnan and Ramanathan (1969) that the X-ray source in Scorpius XR-1 affects the nighttime lower ionosphere of the earth.

Poppoff, I. G.↗
NASA NTRS2000

The Low-Mass Stellar Content of the Scorpius-Centaurus OB Association

Based on ROSAT observations and data obtained with ground-based telescopes, we have carried out an extensive study of the low-mass pre-main-sequence population in Upper Scorpius, the youngest subgroup of the Scorpius-Centaurus OB association.

open clusters and associations galaxy: stellar con↗
NASA NTRS2013

New Brown Dwarf Discs in Upper Scorpius Observed with WISE

We present a census of the disc population for UKIDSS selected brown dwarfs in the 5-10 Myr old Upper Scorpius OB association. For 116 objects originally identified in UKIDSS, the majority of them not studied in previous publications, we obtain photometry from the Wide-Field Infrared Survey Explorer data base. The resulting colour magnitude and colour colour plots clearly show two separate populations of objects, interpreted as brown dwarfs with discs (class II) and without discs (class III). We identify 27 class II brown dwarfs, 14 of them not previously known. This disc fraction (27 out of 116, or 23%) among brown dwarfs was found to be similar to results for K/M stars in Upper Scorpius, suggesting that the lifetimes of discs are independent of the mass of the central object for low-mass stars and brown dwarfs. 5 out of 27 discs (19 per cent) lack excess at 3.4 and 4.6 microns and are potential transition discs (i.e. are in transition from class II to class III). The transition disc fraction is comparable to low-mass stars.We estimate that the time-scale for a typical transition from class II to class III is less than 0.4 Myr for brown dwarfs. These results suggest that the evolution of brown dwarf discs mirrors the behaviour of discs around low-mass stars, with disc lifetimes of the order of 5 10 Myr and a disc clearing time-scale significantly shorter than 1 Myr.

Dawson, P.↗
NASA NTRS2019

Search for Gravitational Waves From Scorpius X-1 in the Second Advanced LIGO Observing Run With an Improved Hidden Markov Model

We present results from a semi coherent search for continuous gravitational waves from the low-mass x-ray binary Scorpius X-1, using a hidden Markov model (HMM) to track spin wandering. This search improves on previous HMM-based searches of LIGO data by using an improved frequency domain matched filter, the J-statistic, and by analyzing data from Advanced LIGO’s second observing run. In the frequency range searched, from 60 to 650 Hz, we find no evidence of gravitational radiation. At 194.6 Hz, the most sensitive search frequency, we report an upper limit on gravitational wave strain (at 95% confidence) ofh95%0¼3.47×10−25when marginalizing over source inclination angle. This is the most sensitive search for Scorpius X-1, to date, that is specifically designed to be robust in the presence of spin wandering.

B P Abbott↗
DOE OSTI2023

Design Aspects of the Emittance Diagnostic for the Scorpius Accelerator

Dear author, This is a reminder that we are expecting you to resubmit your IPAC'23 paper 1268 at https://indico.jacow.org/event/41/papers/2549/ in a format compliant with the IoP guidelines posted at https://publishingsupport.iopscience.iop.org/author-guidelines-for-conference-proceedings/ Could you please upload your paper as a PDF file in the IoP format at https://indico.jacow.org/event/41/papers/2549/ Title: The Design of the Emittance Diagnostic for the Scorpius Accelerator id: 1268 The deadline for resubmitting your paper is July 1st 2023 but we would appreciate if you could submit it earlier. Thank you in advance, Nicolas Delerue on behalf of the IPAC'23 LPR SPB

43 PARTICLE ACCELERATORS↗
DOE OSTI2015

SPITZER IRS SPECTRA OF DEBRIS DISKS IN THE SCORPIUS–CENTAURUS OB ASSOCIATION

We analyze spectra obtained with the Spitzer Infrared Spectrograph (IRS) of 110 B-, A-, F-, and G-type stars with optically thin infrared excess in the Scorpius–Centaurus OB association. The ages of these stars range from 11 to 17 Myr. We fit the infrared excesses observed in these sources by Spitzer IRS and the Multiband Imaging Photometer for Spitzer (MIPS) to simple dust models according to Mie theory. We find that nearly all of the objects in our study can be fit by one or two belts of dust. Dust around lower mass stars appears to be closer in than around higher mass stars, particularly for the warm dust component in the two-belt systems, suggesting a mass-dependent evolution of debris disks around young stars. For those objects with stellar companions, all dust distances are consistent with truncation of the debris disk by the binary companion. The gaps between several of the two-belt systems can place limits on the planets that might lie between the belts, potentially constraining the mass and locations of planets that may be forming around these stars.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

ROTATION PERIODS OF YOUNG BROWN DWARFS: K2 SURVEY IN UPPER SCORPIUS

We report rotational periods for 16 young brown dwarfs in the nearby Upper Scorpius association, based on 72 days of high-cadence, high-precision photometry from the Keplerspace telescope’s K2 mission. The periods range from a few hours to two days (plus one outlier at five days), with a median just above one day, confirming that brown dwarfs, except at the very youngest ages, are fast rotators. Interestingly, four of the slowest rotators in our sample exhibit mid-infrared excess emission from disks; at least two also show signs of disk eclipses and accretion in the light curves. Comparing these new periods with those for two other young clusters and simple angular momentum evolution tracks, we find little or no rotational braking in brown dwarfs between 1–10 Myr, in contrast to low-mass stars. Our findings show that disk braking, while still at work, is inefficient in the substellar regime, thus providing an important constraint on the mass dependence of the braking mechanism.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2018

Beam dynamics for Scorpius with the CDR end-to-end tune: I. Transport

An end-to-end (E2E) simulation of Scorpius was performed for the Conceptual Design Report (CDR). This simulation used a tune significantly different than the tune used for assessing beam stability for the CDR. Since the E2E tune has some desirable features, the stability assessment has been repeated for the E2E tune. In this article I briefly discuss some of the groundwork for the simulations of stable beam transport, and the results. These simulation results show that there is no emittance growth for stable transport with a beam well matched to the magnetic tune. Future articles will cover beam stability that can be expected with E2E tune.

47 OTHER INSTRUMENTATION↗
DOE OSTI2018

Beam Dynamics for Scorpius with the CDR end-to-end tune: II. Short-pulse stability

An end-to-end simulation of Scorpius was performed for the Conceptual Design Report. This simulation used a tune significantly different than the tune used for assessing beam stability. Therefore, the stability assessment has been repeated with the end-to end tune in order to ensure that motion due to instabilities will not significantly blur the radiographic source spot.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2018

Scorpius is being poised to make a sting in stockpile stewardship

Los Alamos is leading a federally directed charge to develop a new facility at the Nevada National Security Site. To study what happens to plutonium during the final stages of a nuclear weapon implosion, the plan calls for Scorpius, which will provide a radiographic capability in a lab 1,000 feet underground.

98 NUCLEAR DISARMAMENT, SAFEGUARDS, AND PHYSICAL P↗
DOE OSTI2019

3D Particle-In-Cell Model of Axis-I: Cathode to Target Single-Code Development for Scorpius

Presentation summary: We are validating the Cathode-to-Target PIC model for Scorpius using Axis-I data and envelope codes. Results include particle transport and phase-space information. Future Work: Charge neutralization and ion focusing via target interactions, (example on next slide) investigation of misalignments of solenoid and accelerating gap fields, and investigation of chromatic effects due to pulsed power fluctuations. The bottom line is determining the impact on spot size.

43 PARTICLE ACCELERATORS↗
DOE OSTI2019

Current Control for Scorpius

There is a need to control the current produced by the Scorpius injector. Reduced beam current aids beam transport, reduces instability growth, mitigates spot-size enlargement due to beam-target interactions, and reduces reflections caused by beam loading of the cells. A method for reducing beam current without major impact on operations or major hardware replacement has been explored through simulations, the results of which are presented.

43 PARTICLE ACCELERATORS↗
DOE OSTI2020

The ASD Scorpius Accelerator at the NNSS. Recruitment Slides for the University of Nevada, Reno [Slides]

The Scorpius Accelerator: Supports the maintenance of the US nuclear stockpile, helps the US not return to nuclear testing, is one of four diagnostics being installed 963 feet below ground, probes subcritical implosions of nuclear material, and supports the validation of LANL and LLNL computer codes. We are searching engineers and scientists with experienced in: Mechanical Engineering, Electrical Engineering, Pulsed Power, Plasma Physics, Controls, Diagnostics, and Fluids and pressure systems.

42 ENGINEERING↗
DOE OSTI2021

Transport of a Low-Energy Beam from the Scorpius Accelerator to the Final-Focus Solenoid

It may be required to use Scorpius for low-energy radiography of hydrodynamic experiments, perhaps as low as the 2-MeV injected beam kinetic energy. As presently designed, the downstream transport (DST) system will not work for energies less than about 4.5 MeV due to space-charge defocusing. For energies less than that the beam envelope expands to the wall before the first magnet can catch and focus it. More solenoids would have to be added to the DST lattice in order to transport a beam with KE < 4.5 MeV to the final focus.

43 PARTICLE ACCELERATORS↗