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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 289 records · Page 16
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

ARMADA. I. Triple Companions Detected in B-type Binaries α Del and ν Gem

Ground-based optical long-baseline interferometry has the power to measure the orbits of close binary systems at ∼10 μas precision. This precision makes it possible to detect “wobbles” in the binary motion due to the gravitational pull from additional short-period companions. We started the ARrangement for Micro-Arcsecond Differential Astrometry (ARMADA) survey with the Michigan Infra-Red Combiner (MIRC)/MIRC-X instrument at the Center for High Angular Resoloution Astronomy (CHARA) array for the purpose of detecting giant planets and stellar companions orbiting individual stars in binary systems. We describe our observations for the survey, and introduce the wavelength calibration scheme that delivers precision at the tens of microarcseconds level for <02 binaries. We test our instrument performance on a known triple system, κ Peg, and show that our survey is delivering a factor of 10 better precision than previous similar surveys. We present astrometric detections of tertiary components to two B-type binaries: a 30 day companion to α Del, and a 50 day companion to ν Gem. We also collected radial velocity data for α Del with the Tennessee State University Automated Spectroscopic Telescope at Fairborn Observatory. We are able to measure the orbits and masses of all three components in these systems. We find that the previously published radial velocity orbit for the inner pair of ν Gem is not consistent with our visual orbit. The precision achieved for these orbits suggests that our ARMADA survey will be successful at discovering new compact triple systems to A/B-type binary systems, leading to better statistics of hierarchical system architectures and formation history.

47 OTHER INSTRUMENTATION↗
NASA NTRS1976

Effects of tidal distortion on binary-star velocity curves and ellipsoidal variation

Radial velocity curves for the more massive components of binaries with extreme mass ratios can show a large distortion due to tides, as first recognized by Sterne. Binaries in which the effect is large should be rare because nearly all such binaries would be in the rapid phase of mass transfer. However, the optical counterparts of some X-ray binaries may show the effect, which would then serve as a new means of extracting considerable information from the observations. The essential parts of the computational procedure are given. Light curves for ellipsoidal variables with extreme mass ratios were also computed, and were found to be less sinusoidal than those with normal mass ratios.

Wilson, R. E.↗
DOE OSTI2013

ADAPTIVE OPTICS IMAGES. II. 12 KEPLER OBJECTS OF INTEREST AND 15 CONFIRMED TRANSITING PLANETS

All transiting planet observations are at risk of contamination from nearby, unresolved stars. Blends dilute the transit signal, causing the planet to appear smaller than it really is, or producing a false positive detection when the target star is blended with an eclipsing binary. High spatial resolution adaptive optics images are an effective way of resolving most blends. Here we present visual companions and detection limits for 12 Kepler planet candidate host stars, of which 4 have companions within 4''. One system (KOI 1537) consists of two similar-magnitude stars separated by 0.''1, while KOI 174 has a companion at 0.''5. In addition, observations were made of 15 transiting planets that were previously discovered by other surveys. The only companion found within 1'' of a known planet is the previously identified companion to WASP-2b. An additional four systems have companions between 1'' and 4'': HAT-P-30b (3.''7, {Delta}Ks = 2.9), HAT-P-32b (2.''9, {Delta}Ks = 3.4), TrES-1b (2.''3, {Delta}Ks = 7.7), and WASP-P-33b (1.''9, {Delta}Ks = 5.5), some of which have not been reported previously. Depending on the spatial resolution of the transit photometry for these systems, these companion stars may require a reassessment of the planetary parameters derived from transit light curves. For all systems observed, we report the limiting magnitudes beyond which additional fainter objects located 0.''1-4'' from the target may still exist.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2016

RESOLVED COMPANIONS OF CEPHEIDS: TESTING THE CANDIDATES WITH X-RAY OBSERVATIONS

We have made XMM-Newton observations of 14 Galactic Cepheids that have candidate resolved (≥5″) companion stars based on our earlier HST Wide Field Camera 3 (WFC3) imaging survey. Main-sequence stars that are young enough to be physical companions of Cepheids are expected to be strong X-ray producers in contrast to field stars. XMM-Newton exposures were set to detect essentially all companions hotter than spectral type M0 (corresponding to 0.5 M{sub ⊙}). The large majority of our candidate companions were not detected in X-rays, and hence are not confirmed as young companions. One resolved candidate (S Nor #4) was unambiguously detected, but the Cepheid is a member of a populous cluster. For this reason, it is likely that S Nor #4 is a cluster member rather than a gravitationally bound companion. Two further Cepheids (S Mus and R Cru) have X-ray emission that might be produced by either the Cepheid or the candidate resolved companion. A subsequent Chandra observation of S Mus shows that the X-rays are at the location of the Cepheid/spectroscopic binary. R Cru and also V659 Cen (also X-ray bright) have possible companions closer than 5″ (the limit for this study) which are the likely sources of X-rays. One final X-ray detection (V473 Lyr) has no known optical companion, so the prime suspect is the Cepheid itself. It is a unique Cepheid with a variable amplitude. The 14 stars that we observed with XMM constitute 36% of the 39 Cepheids found to have candidate companions in our HST/WFC3 optical survey. No young probable binary companions were found with separations of ≥5″ or 4000 au.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2021

Method to synthesize nanoparticle supercrystals

Highly ordered arrays of 3D faceted nanoparticle supercrystals are formed by self-assembly with controlled nanoparticle packing and unique facet dependent optical property by using a binary solvent diffusion method. The binary diffusion results in supercrystals whose size and quality are determined by initial nanoparticle concentration and diffusion speed. The supercrystal solids display unique facet-dependent surface plasmonic and surface-enhanced Raman characteristics. The supercrystals have potential applications in areas such as optics, electronics, and sensor platforms.

Fan, Hongyou↗
DOE OSTI2020

Binary pseudorandom array test standard optimized for characterization of large field-of-view optical interferometers

Recently, a technique for calibrating the modulation transfer function (MTF) of a broad variety of metrology instrumentation has been demonstrated. This technique is based on test samples structured as one-dimensional binary pseudo-random (BPR) sequences and two-dimensional BPR arrays (BPRAs). The inherent power spectral density of BPR gratings (sequences) and arrays has a deterministic white-noise-like character that allows direct determination of the MTF with uniform sensitivity over the entire spatial frequency range and field-of-view of an instrument. As such, the BPR samples satisfy the characteristics of a test standard: functionality, ease of specification and fabrication, reproducibility, and low sensitivity to manufacturing error. Here we discuss our recent developments directed to the optimization of the sample design, fabrication, application, and data processing procedures, suitable for thorough characterization of large aperture optical interferometers. Compared with the previous coded-aperture based design, the improved, 'highly randomized' BPRA pattern of the new test standard provides better accuracy and reliability of instrument MTF and aberration characterization, and enables operation optimization of large aperture optical interferometers. We describe the pattern generation algorithm and tests to verify the compliance to desired BPRA topography. The data acquisition and analysis procedures for different applications of the technique are also discussed.

Yashchuk, Valeriy V.↗
NASA NTRS1982

A search for cataclysmic binaries containing strongly magnetic white dwarfs

The AM Herculis type binaries which contain accreting white dwarfs with surface magnetic fields of a few times 10 to the seventh power gauss were studied. If white dwarfs in cataclysmic binaries have a range of field strengths similar to that among single white dwarfs. AM Her like systems should exist with fields as high as 3 x 10 to the eighth power gauss. It is suggested that such objects will not have the strong optical polarization of the AM Her variables; however, they exhibit high harmonic cyclotron emission, making them spectacular UV sources. We made IUE observations of seven candidate cataclysmic variables selected for optical similarity to AM Her binaries. Although all seven objects were detected in the UV, none display unusually strong UV continua. It is suggested that the distribution of magnetic field strengths among single white dwarfs may be different from that among binaries.

Bond, H. E.↗
NASA NTRS1992

Effects and correction of magneto-optic spatial light modulator phase errors in an optical correlator

The optical phase errors introduced into an optical correlator by the input and filter plane magnetooptic spatial light modulators have been studied. The magnitude of these phase errors is measured and characterized, their effects on the correlation results are evaluated, and a means of correction by a design modification of the binary phase-only optical-filter function is presented. The efficacy of the phase-correction technique is quantified and is found to restore the correlation characteristics to those obtained in the absence of errors, to a high degree. The phase errors of other correlator system elements are also discussed and treated in a similar fashion.

Downie, John D.↗
NASA NTRS1984

Accretion disk limit cycle mechanism in twin-degenerate interacting binaries

Accretion disk instability is studied as a possible mechanism causing large variations in the optical light curves of twin-degenerate interacting binary stars. The nonthermal equilibrium limit cycle behavior of the accretion disk expected for such a binary system is explored using a generalized time-dependent, nonthermal equilibrium accretion disk model developed for the study of dwarf novae. A series of bursts is computed for a wide range of values of the secondary mass transfer rate, and the results are presented and discussed.

Cannizzo, J. K.↗
NASA NTRS1981

Ultraviolet spectroscopy of old novae and symbiotic stars

The IUE spectra are presented for two old novae and for two of the symbiotic variables. Prominent emission line spectra are revealed as a continuum whose appearance is effected by the system inclination. These data provide evidence for hot companions in the symbiotic stars, making plausible the binary model for these peculiar stars. Recent IUE spectra of dwarf novae provide additional support for the existence of optically thick accretion disks in active binary systems. The ultraviolet data of the eclipsing dwarf novae EX Hya and BV Cen appear flatter than for the noneclipsing systems, an effect which could be ascribed to the system inclination.

Lambert, D. L.↗
NASA NTRS1989

Acousto-optical/Magneto-optical Correlator Or Convolver

Experimental system demonstrates optical processing of multiple channels of binary signals. One input channel contains signal that varies with time and applied to one-dimensional acousto-optical cell. Other input channel contains two-dimensional pattern that is stationary or can vary with time and applied to magneto-optical spatial light modulator. Output is time-varying correlation or convolution of first input with one of rows in second input.

Liu, Hua-Kuang↗
DOE OSTI2010

THE Be STAR HD 215227: A CANDIDATE GAMMA-RAY BINARY

The emission-line Be star HD 215227 lies within the positional error circle of the newly identified gamma-ray source AGL J2241+4454. We present new blue spectra of the star, and we point out the morphological and variability similarities to other Be binaries. An analysis of the available optical photometry indicates a variation with a period of 60.37 {+-} 0.04 days, which may correspond to an orbital modulation of the flux from the disk surrounding the Be star. The distance to the star of 2.6 kpc and its relatively large Galactic latitude suggest that the binary was ejected from the plane by a supernova explosion that created the neutron star or black hole companion. The binary and runaway properties of HD 215227 make it an attractive candidate as the optical counterpart of AGL J2241+4454 and as a new member of the small class of gamma-ray emitting binaries.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2012

OPTICAL AND NEAR-INFRARED MONITORING OF THE BLACK HOLE X-RAY BINARY GX 339-4 DURING 2002-2010

We present the optical/infrared (O/IR) light curve of the black hole X-ray binary GX 339-4 collected at the SMARTS 1.3 m telescope from 2002 to 2010. During this time the source has undergone numerous state transitions including hard-to-soft state transitions when we see large changes in the near-IR flux accompanied by modest changes in optical flux, and three rebrightening events in 2003, 2005, and 2007 after GX 339-4 transitioned from the soft state to the hard. All but one outburst show similar behavior in the X-ray hardness-intensity diagram. We show that the O/IR colors follow two distinct tracks that reflect either the hard or soft X-ray state of the source. Thus, either of these two X-ray states can be inferred from O/IR observations alone. From these correlations we have constructed spectral energy distributions of the soft and hard states. During the hard state, the near-IR data have the same spectral slope as simultaneous radio data when GX 339-4 was in a bright optical state, implying that the near-IR is dominated by a non-thermal source, most likely originating from jets. Non-thermal emission dominates the near-IR bands during the hard state at all but the faintest optical states, and the fraction of non-thermal emission increases with increasing optical brightness. The spectral slope of the optical bands indicate that a heated thermal source is present during both the soft and hard X-ray states, even when GX 339-4 is at its faintest optical state. We have conducted a timing analysis of the light curve for the hard and soft states and find no evidence of a characteristic timescale within the range of 4-230 days.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

High resolution imaging of very low mass spectral binaries: Three resolved systems and detection of orbital motion in an L/T transition binary

We present high resolution Laser Guide Star Adaptive Optics imaging of 43 late-M, L and T dwarf systems with Keck/NIRC2. These include 17 spectral binary candidates, systems whose spectra suggest the presence of a T dwarf secondary. We resolve three systems: 2MASS J1341–3052, SDSS J1511+0607 and SDSS J2052–1609; the first two are resolved for the first time. All three have projected separations <8 AU and estimated periods of 14–80 years. We also report a preliminary orbit determination for SDSS J2052–1609 based on six epochs of resolved astrometry between 2005 and 2010. Among the 14 unresolved spectral binaries, 5 systems were confirmed binaries but remained unresolved, implying a minimum binary fraction of 47{sub −11}{sup +12}% for this sample. Our inability to resolve most of the spectral binaries, including the confirmed binaries, supports the hypothesis that a large fraction of very low mass systems have relatively small separations and are missed with direct imaging.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2012

THE NATURE AND EVOLUTIONARY STATE OF THE FU ORIONIS BINARY SYSTEM

In this paper, we present the results of our adaptive optics fed three-dimensional imaging spectroscopy study of the FU Orionis binary system. Although the 0.''5 separation companion to FU Ori is {approx}4 mag fainter, we have easily spatially resolved it in the J, H, and K infrared bands and extract high signal-to-noise spectra of the two stellar components from 1.15 to 2.4 {mu}m. We derive a spectral type of K5{sup +2}{sub -1} for FU Ori S based on the stellar photospheric absorption features and find that it is an actively accreting young star (M-dot{sub acc}{approx} (2-3) Multiplication-Sign 10{sup -8} M{sub Sun} yr{sup -1}) that is likely gravitationally bound to FU Ori. We have found that the continuum shape of FU Ori S is not well fit by our spectral modeling process, and this results in a large uncertainty in the line-of-sight extinction to the star. Yet, by placing FU Ori S on the Hertzsprung-Russell diagram and comparing its estimated location with evolutionary models, we find that it is best fit as a {approx}1.2 M{sub Sun} star with a likely age of less than {approx}2 Myr. If we assume coevality of the stellar components, we have thus placed an estimated age on the FU Ori system. Moreover, assuming the canonical model for the nature of FU Ori in that its optical and infrared absorption features arise primarily from the inner circumstellar disk around a {approx}0.3 M{sub Sun} star, we find that the fainter FU Ori S component is actually the more massive star in the system. Future monitoring of FU Ori S to investigate flux variability and orbital motion should further clarify the nature of this curious young binary.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2010

Solvothermal Synthesis, Structure and Optical Property of Nanosized CoSb 3 Skutterudite

Binary skutterudite CoSb 3 nanoparticles were synthesized by solvothermal method. The nanostructuring of CoSb 3 material was achieved by the inclusion of various kinds of additives. X-ray diffraction examination indicated the formation of the cubic phase of CoSb 3 . Structural analysis by transmission electron microscopy analysis further confirmed the formation of crystalline CoSb 3 nanoparticles with high purity. With the assistance of additives, CoSb 3 nanoparticles with size as small as 10 nm were obtained. The effect of the nanostructure of CoSb 3 on the UV–visible absorption and luminescence was studied. The nanosized CoSb 3 skutterudite may find application in developing thermoelectric devices with better efficiency.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗