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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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6 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

BVR{sub C}I{sub C} Observations and Analysis of the UV LEO-type Binary, the Pre-WUMa, V1023 Persei

V1023 Per is a polar spotted, but well-detached dwarf binary, very likely a Pre-WUMa eclipsing binary. It was observed on 11 nights in 2015 October, November, and December at Dark Sky Observatory in North Carolina with the 0.81 m reflector of Appalachian State University. The period behavior is complex and may be increasing with a cubic or quadratic ephemeris. Its odd light curves are of high amplitude but have no totality and reach maximum light just before and following the secondary eclipse, indicating that it has polar spots similar to UV Leo. The 28 yr orbital period study calls the attention of observers to further monitor this binary to understand the complex nature of the period evolution. Its presently fixed polar spot does indicate that it must have a strong magnetic field and that it is synchronously rotating. The BVR{sub c}I{sub c} simultaneous 2016 Wilson–Devinney program (W-D) solution gives fillouts of 68% and 75% for the primary and secondary components, respectively. The polar position of the spot, its radius (24°), and T-fact (0.75) indicate that a strong magnetic field is present. The small ΔT in the components (∼289 K) show that the stars are similar in spectral type despite them being well detached. The inclination is high, ∼85.°19 ± 0.°04, but there is not a total eclipse due to the high mass ratio (∼0.739 ± 0.001). Due to the low galactic position (longitude = 150.°390, latitude = −1.°023), its reddening is addressed. The primary components temperature is estimated to be 5250 ± 250 K.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2021

Double Image Polarimeter—Ultra Fast: Simultaneous Three-color (BVR) Polarimeter with Electron-multiplying Charge-coupled Devices

We describe a new instrument capable of high-precision (10{sup −5}) polarimetric observations simultaneously in three passbands (BVR). The instrument utilizes electron-multiplying charge-coupled device (EM CCD) cameras for high efficiency and fast image readout. The key features of the Double Image Polarimeter—Ultra Fast (DIPol-UF) are: (i) the optical design with high throughput and inherent stability; (ii) great versatility, which makes the instrument optimally suitable for observations of bright and faint targets; and (iii) a control system, which allows the use of the polarimeter remotely. Examples are given of the first results obtained from high signal-to-noise observations of bright nearby stars and of fainter sources such as X-ray binaries in their quiescent states.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2021

BVR{sub c}I{sub c} Observations, Third-body Orbital Study, and Analysis of the UV Leo-type, Pre-W UMA Binary V642 Virginis

V642 Vir is a polar spotted, well-detached, UV Leo-type, low-mass, pre-WUMa (T1 ~ 4250K, ~K6V) eclipsing binary. It was observed in 2020 April, May, and June at the Dark Sky Observatory in North Carolina, USA with the 0.81 m reflector of Appalachian State University. A total of 88 timings were used in our 22-year period study which included 12 Transiting Exoplanet Survey Satellite (TESS) timings. The O - C plots show a low-amplitude oscillation of residuals that points to the existence of an orbiting third body, a dwarf of minimum mass, 0.15 M {sub ⊙} in an eccentric orbit (e = 0.41), with an orbital period of 20.07 yr. The odd light curves of V642 Virginis indicate that it has polar spots similar to UV Leo and the recently published V1023 Per. Its present large polar spot region indicates that it must have a strong magnetic field and that it is synchronously rotating. The BVR{sub c}I{sub c} simultaneous Wilson–Devinney Program solution gives a detached binary (primary and secondary components are underfilling their respective Roche Lobes, with 76% and 78% fill outs respectively). The cool spot region models near the pole of the primary component (centered at 10° colatitude) and is angled toward the secondary component. Its large radius (68°) and T-fact (T{sub spot}/T{sub surface} = 0.69) also attest to the conclusion of the strength of the magnetic field. The small ΔT in the components (~318 K) and mass ratio near unity (0.9542 ± 0.0005) show that the stars are similar in spectral type (secondary ~K9V). The inclination is high, ~86.87 ± 0.04°, yet there is no time of constant light due to the two stars’ essentially equal radii.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2020

Experimental methodology and theoretical framework in describing constrained plastic flow of FCC microscale tensile specimens

Small scale mechanical testing (SSMT) allows for the quantification of the mechanical responses for microscale and nanoscale material volumes. It has significant potential in improving our fundamental understanding of plastic deformation and in providing an engineering solution for testing complex and/or critical materials. Importantly, previous studies have revealed that plastic intermittency, manifested as strain bursts, are characteristic of the plastic flow behavior at the small length scale. In this work, interfacial constraint has been utilized to suppress strain bursts in order to stabilize plasticity. A new parameter, blocked volume ratio (BVR), is introduced to quantify the degree of constraint for a microscale specimen due to an interface. Here, we showed that the plastic flow behavior in FCC Ni-based metals is highly dependent on the BVR of the specimen.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Photometric and Kinematic Study of the Open Clusters SAI 44 and SAI 45

We carry out a detailed photometric and kinematic study of the poorly studied sparse open clusters SAI 44 and SAI 45 using ground-based BVR {sub c} I {sub c} data supplemented by archival data from Gaia eDR3 and Pan-STARRS. The stellar memberships are determined using a statistical method based on Gaia eDR3 kinematic data, and we found 204 members in SAI 44 while only 74 members are identified in SAI 45. The average distances to SAI 44 and SAI 45 are calculated to be 3670 ± 184 and 1668 ± 47 pc. The logarithmic age of the clusters are determined to be 8.82 ± 0.10 and 9.07 ± 0.10 yr for SAI 44 and SAI 45, respectively. The color–magnitude diagram of SAI 45 hosts an extended main-sequence turnoff (eMSTO). The apparent age spread is found to be similar to the apparent age spread predicted on the basis of the age spread and cluster age relation predicted by rotation models. This indicates that eMSTO is a stellar evolution rather than star formation phenomenon in SAI 45. We conclude that eMSTO in SAI 45 is mainly caused by the different rotation rates of stars as the SYCLIST synthetic population with different rotation rates was able to reproduce the observed eMSTO, and stars in the red part of the eMSTO were preferentially concentrated in the inner region, which again hints at different rotations being the reason for the extension in the upper MS. This finding supports the theory attributing the origin of eMSTO to the different rotations of eMSTO stars. The mass function slopes are obtained as -2.24 ± 0.66 and -2.58 ± 3.20 in the mass rages 2.426–0.990 M{sub ⊙} and 2.167–1.202 M{sub ⊙} for SAI 44 and SAI 45, respectively. SAI 44 exhibits the signature of mass segregation while we found weak evidence of mass segregation in SAI 45 possibly due to tidal stripping. The dynamical relaxation times of these clusters indicate that both clusters are in a dynamically relaxed state. Using the AD-diagram method, the apex coordinates are found to be ([[Formula]], -[[Formula]]) for SAI 44 and (-[[Formula]], -[[Formula]]) for SAI 45. The average space velocity components of the clusters SAI 44 and SAI 45 are calculated in units of km s{sup -1} as (-15.14 ± 3.90, -19.43 ± 4.41, -20.85 ± 4.57) and (28.13 ± 5.30, -9.78 ± 3.13, -19.59 ± 4.43), respectively.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗