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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 343 records · Page 19
All sourcesNASA NTRSDOE OSTI
DOE OSTI2011

DUST GRAIN EVOLUTION IN SPATIALLY RESOLVED T TAURI BINARIES

Core-accretion planet formation begins in protoplanetary disks with the growth of small, interstellar medium dust grains into larger particles. The progress of grain growth, which can be quantified using 10 {mu}m silicate spectroscopy, has broad implications for the final products of planet formation. Previous studies have attempted to correlate stellar and disk properties with the 10 {mu}m silicate feature in an effort to determine which stars are efficient at grain growth. Thus far there does not appear to be a dominant correlated parameter. In this paper, we use spatially resolved adaptive optics spectroscopy of nine T Tauri binaries as tight as 0.''25 to determine if basic properties shared between binary stars, such as age, composition, and formation history, have an effect on dust grain evolution. We find with 90%-95% confidence that the silicate feature equivalent widths of binaries are more similar than those of randomly paired single stars, implying that shared properties do play an important role in dust grain evolution. At lower statistical significance, we find with 82% confidence that the secondary has a more prominent silicate emission feature (i.e., smaller grains) than the primary. If confirmed by larger surveys, this would imply that spectral type and/or binarity are important factors in dust grain evolution.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1993

PG 0308 + 096 and PG 1026 + 002 - Two new short period binary stars resulting from common-envelope evolution

Ultraviolet spectroscopy, optical spectroscopy, and spectrophotometry have been used to study the excess UV stars PG 0308 + 096 and PG 1026 + 002. Both objects are short-period binary systems, each containing a DA white dwarf star and a dM star. Orbital periods of approximately 0.284 day for PG 0308 + 096, and aproximately 0.597 day for PG 1026, have been found by spectroscopic analysis of the H-alpha emission line. Ly-alpha and Balmer line profile fitting were used to estimate the mass of white dwarf stars; mass estimates for the dM stars are based on their spectral types. The orbital inclinations are derived from these masses, the periods, and amplitudes of the H-alpha radial velocity curves. The equivalent width of the H-alpha emission line, in each binary system, varies with the orbital phase in such a manner as to imply that it arises, in large part at least, from the hemisphere of the M star that faces the white dwarf star.

Saffer, Rex A.↗
NASA NTRS1975

Data processing large quantities of multispectral information

Method is combination of digital and optical techniques. Multispectral data is coded into binary matrix format and then encoded onto photographic film. Film is holographically correlated with spectral signature to generate single-class classification map. Number of maps are optically superimposed to produce full-color, multiclass classification map.

Haskell, R. E.↗
DOE OSTI2014

Orbital motion in pre-main sequence binaries

We present results from our ongoing program to map the visual orbits of pre-main sequence (PMS) binaries in the Taurus star forming region using adaptive optics imaging at the Keck Observatory. We combine our results with measurements reported in the literature to analyze the orbital motion for each binary. We present preliminary orbits for DF Tau, T Tau S, ZZ Tau, and the Pleiades binary HBC 351. Seven additional binaries show curvature in their relative motion. Currently, we can place lower limits on the orbital periods for these systems; full solutions will be possible with more orbital coverage. Five other binaries show motion that is indistinguishable from linear motion. We suspect that these systems are bound and might show curvature with additional measurements in the future. The observations reported herein lay critical groundwork toward the goal of measuring precise masses for low-mass PMS stars.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2017

Physical properties of madocite: A quaternary chalcogenide with very low thermal conductivity

The madocite Pb{sub 17}(Sb{sub 0.75}As{sub 0.25}){sub 16}S{sub 41} was synthesized by reaction of binary compounds and densified using hot pressing. The optical band-gap, thermal stability, and temperature-dependent heat capacity and thermal conductivity are reported for the first time. The thermal properties are evaluated using the Debye model. The findings in this work lay the foundation for a more detailed understanding of the physical properties of this material, and is part of the continuing effort in investigating materials with new compositions that possess low thermal conductivity for potential low-cost thermal barrier coating and energy-related applications. - Graphical abstract: The report describes the synthesis and physical properties characterization of Pb{sub 17}(Sb{sub 0.75}As{sub 0.25}){sub 16}S{sub 41}, a quaternary chalcogenide with the madocite crystal structure that possesses a low thermal conductivity, for the first time. The compositions was synthesized by reaction of binary compounds and densified using hot pressing. Optical band-gap, thermal stability, and temperature-dependent heat capacity measurements are also discussed. - Highlights: • Pb{sub 17}(Sb{sub 0.75}As{sub 0.25}){sub 16}S{sub 41} was synthesized by reaction of binary compounds and densified using hot pressing. • We report the characterizations of this quaternary chalcogenide that possesses a low thermal conductivity for the first time. • The optical band-gap, thermal stability, and temperature-dependent heat capacity are also investigated for the first time.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1982

Results of the IUE program of monitoring the ultraviolet emission line fluxes of four binary systems: HR 1099, 2 Peg, AR Lac and By Dra

A program to obtain IUE spectra and optical photometry and spectra of three RS CVn-type binaries (HR 1099, II Peg, and AR Lac) and the prototype BY Dra system is reported. The systems were monitored for at least one orbital phase, and periodic variations in emission line flux from II Peg and HR 1099, indicative of notational modulation of an active region on these stars were detected. It is found that for II Peg the active region is in phase with photometric minimum as expected, but for HR 1099 ultraviolet emission maximum occurs at the time of photometric maximum.

Marstad, M.↗
DOE OSTI2013

ULTRA-STRIPPED TYPE Ic SUPERNOVAE FROM CLOSE BINARY EVOLUTION

Recent discoveries of weak and fast optical transients raise the question of their origin. We investigate the minimum ejecta mass associated with core-collapse supernovae (SNe) of Type Ic. We show that mass transfer from a helium star to a compact companion can produce an ultra-stripped core which undergoes iron core collapse and leads to an extremely fast and faint SN Ic. In this Letter, a detailed example is presented in which the pre-SN stellar mass is barely above the Chandrasekhar limit, resulting in the ejection of only ∼0.05-0.20 M {sub ☉} of material and the formation of a low-mass neutron star (NS). We compute synthetic light curves of this case and demonstrate that SN 2005ek could be explained by our model. We estimate that the fraction of such ultra-stripped to all SNe could be as high as 10{sup –3}-10{sup –2}. Finally, we argue that the second explosion in some double NS systems (for example, the double pulsar PSR J0737–3039B) was likely associated with an ultra-stripped SN Ic.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1976

Bit-error rates in optical communications

Statistical model, which consists of on/off binary system, assumes Poisson detection process and log-normal atmospheric scintillation. Based upon detection process and atmospheric ionization, piecewise linear model for adaptive threshold system is developed.

Webb, W. E.↗
DOE OSTI2011

A MULTIWAVELENGTH STUDY OF BINARY QUASARS AND THEIR ENVIRONMENTS

We present Chandra X-ray imaging and spectroscopy for 14 quasars in spatially resolved pairs targeted as part of a complete sample of binary quasars with small transverse separations drawn from Sloan Digital Sky Survey (SDSSDR6) photometry. We measure the X-ray properties of all 14 QSOs, and study the distribution of X-ray and optical-to-X-ray power-law indices in these binary quasars. We find no significant difference when compared with large control samples of isolated quasars, true even for SDSS J1254+0846, discussed in detail in a companion paper, which clearly inhabits an ongoing, pre-coalescence galaxy merger showing obvious tidal tails. We present infrared photometry from our observations with SAO Wide-field InfraRed Camera at the MMT, and from the Wide-field Infrared Survey Explorer Preliminary Data Release, and fit simple spectral energy distributions to all 14 QSOs. We find preliminary evidence that substantial contributions from star formation are required, but possibly no more so than for isolated X-ray-detected QSOs. Sensitive searches of the X-ray images for extended emission and the optical images for optical galaxy excess show that these binary QSOs-expected to occur in strong peaks of the dark matter distribution-are not preferentially found in rich cluster environments. While larger binary QSO samples with richer far-IR and submillimeter multiwavelength data might better reveal signatures of merging and triggering, optical color selection of QSO pairs may be biased against such signatures. X-ray and/or variability selection of QSO pairs, while challenging, should be attempted. We present in an Appendix a primer on X-ray flux and luminosity calculations.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2012

IDENTIFICATION OF GALACTIC BULGE SURVEY X-RAY SOURCES WITH TYCHO-2 STARS

We identify 69 X-ray sources discovered by the Galactic Bulge Survey (GBS) that are coincident with or very close to bright stars in the Tycho-2 catalog. Additionally, two other GBS sources are resolved binary companions to Tycho-2 stars where both components are separately detected in X-rays. Most of these are likely to be real matches, but we identify nine objects with large and significant X-ray-to-optical offsets as either detections of resolved binary companions or chance alignments. We collate known spectral types for these objects, and also examine Two Micron All Sky Survey colors, variability information from the All-Sky Automated Survey, and X-ray hardness ratios for the brightest objects. Nearly a third of the stars are found to be optically variable, divided roughly evenly between irregular variations and periodic modulations. All fall among the softest objects identified by the GBS. The sample forms a very mixed selection, ranging in spectral class from O9 to M3. In some cases, the X-ray emission appears consistent with normal coronal emission from late-type stars, or wind emission from early-types, but the sample also includes one known Algol, one W UMa system, two Be stars, and several X-ray bright objects likely to be coronally active stars or binaries. Surprisingly, a substantial fraction of the spectroscopically classified, non-coincidental sample (12 out of 38 objects) have late B or A type counterparts. Many of these exhibit redder near-IR colors than expected for their spectral type and/or variability, and it is likely that the X-rays originate from a late-type companion star in most or all of these objects.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1994

Spectroscopic, orbital, and physical properties of the binary Feige 24 and detection of transient He II absorption in the system

We have obtained new high-dispersion optical spectroscopy at Kitt Peak National Observatory (KPNO) and new International Ultraviolet Explorer (IUE) spectroscopy of the white dwarf+red dwarf binary system Feige 24. The optical range shows a composite DA+dM spectrum, together with H I Balmer and He I emission. The orbital phase dependence of the emission shows that it results from extreme ultraviolet (EUV) light reprocessing in the red dwarf upper atmosphere. The systems close enough and hot enough to show this reprocessing signature only recently emerged from common-envelope evolution. The ultraviolet spectrum exclusively emanates from the white dwarf and shows numerous heavy element absorption lines. We measured accurate radial velocities of the red dwarf component motion, traced by both optical absorption and emission lines, and new radial velocities of the white dwarf, traced by ultraviolet Fe V lines. Combining these measurements, we refined the orbital parameters presented by Vennes et al. (1991), and we confirmed that the white dwarf gravitational redshift is exceptionally small with 9 +/- 2 km/s. From this we deduced that the interior is either pure helium or carbon with a thick hydrogen layer, and we derived, for the combined interior compositions, a white dwarf mass and radius of M(sub WD) = 0.44-050 solar mass and R(sub WD) = 0.028-0.036 solar radius. We suggest that Feige 24 could be a typical case of close binary evolution leading to the formation of a low-mass helium white dwarf. The mass of the red dwarf and the inclination of the system naturally follow: M(sub dM) = 0.26-0.33 solar mass, i greater than or equal to 75 deg. High-dispersion H-alpha line profiles are asymmetrical, strongly enhanced toward the blue, suggesting a moving atmosphere possibly linked to a mass loss rate of 10(exp -10) solar mass/yr. The IUE spectra taken when the system is near inferior conjunction show strong He II 1640 A absorption. The profile is highly variable in width and intensity. Because it is correlated with the passage of the white dwarf at inferior conjunction, the absorption may occur in some foreground plasma emanated by the red dwarf and accumulating near a Lagrangian point or, alternatively, it may originate in an accretion spot on the white dwarf surface coaligned with the major orbital axis. Either way, the He II detection may imply substantial mass loss from the red dwarf with a corollary reclassification of Feige 24 as a mixed He/H DAO white dwarf resulting from accretion of secondary mass-loss material. Feige 24 is the prototype of a class of young, EUV-emitting, binary systems comprising a late main sequence secondary and a hot H-rich white dwarf; the class is characterized by optical and ultraviolet photospheric He II absorption, circumstellar C IV lambda (1550) absorption, and by the presence of EUV-induced, phase-dependent Balmer fluorescence. These young systems present the best opportunity to constrain theory of common-envelope evolution.

Vennes, Stephane↗
DOE OSTI2022

Measuring the mass of the black widow PSR J1555-2908

ABSTRACT Accurate measurements of the masses of neutron stars are necessary to test binary evolution models, and to constrain the neutron star equation of state. In pulsar binaries with no measurable post-Keplerian parameters, this requires an accurate estimate of the binary system’s inclination and the radial velocity of the companion star by other means than pulsar timing. In this paper, we present the results of a new method for measuring this radial velocity using the binary synthesis code Icarus. This method relies on constructing a model spectrum of a tidally distorted, irradiated star as viewed for a given binary configuration. This method is applied to optical spectra of the newly discovered black widow PSR J1555–2908. By modeling the optical spectroscopy alongside optical photometry, we find that the radial velocity of the companion star is 397 ± 4 km s−1 (errors quoted at 95 per cent confidence interval), as well as a binary inclination of >75°. Combined with γ-ray pulsation timing information, this gives a neutron star mass of 1.67$^{+0.15}_{-0.09}$ M⊙ and a companion mass of 0.060$^{+0.005}_{-0.003}$ M⊙, placing PSR J1555–2908 at the observed upper limit of what is considered a black widow system.

Kennedy, M. R.↗
DOE OSTI2015

SIMULTANEOUS MULTIWAVELENGTH OBSERVATIONS OF MAGNETIC ACTIVITY IN ULTRACOOL DWARFS. IV. THE ACTIVE, YOUNG BINARY NLTT 33370 AB (= 2MASS J13142039+1320011)

We present multi-epoch simultaneous radio, optical, Hα, UV, and X-ray observations of the active, young, low-mass binary NLTT 33370 AB (blended spectral type M7e). This system is remarkable for its extreme levels of magnetic activity: it is the most radio-luminous ultracool dwarf (UCD) known, and here we show that it is also one of the most X-ray luminous UCDs known. We detect the system in all bands and find a complex phenomenology of both flaring and periodic variability. Analysis of the optical light curve reveals the simultaneous presence of two periodicities, 3.7859 ± 0.0001 and 3.7130 ± 0.0002 hr. While these differ by only ∼2%, studies of differential rotation in the UCD regime suggest that it cannot be responsible for the two signals. The system's radio emission consists of at least three components: rapid 100% polarized flares, bright emission modulating periodically in phase with the optical emission, and an additional periodic component that appears only in the 2013 observational campaign. We interpret the last of these as a gyrosynchrotron feature associated with large-scale magnetic fields and a cool, equatorial plasma torus. However, the persistent rapid flares at all rotational phases imply that small-scale magnetic loops are also present and reconnect nearly continuously. We present a spectral energy distribution of the blended system spanning more than 9 orders of magnitude in wavelength. The significant magnetism present in NLTT 33370 AB will affect its fundamental parameters, with the components' radii and temperatures potentially altered by ∼+20% and ∼–10%, respectively. Finally, we suggest spatially resolved observations that could clarify many aspects of this system's nature.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1993

A spectroscopic search for colliding stellar winds in O-type close binary systems. III - 29 UW Canis Majoris

The orbital-phase variations in the optical emission lines and UV P Cygni lines of the massive O-type binary 29 UW Canis Majoris are investigated in a search for evidence of colliding winds. High SNR spectra of the H-alpha and He I 6678-A emission lines are presented, and radial velocity curves for several features associated with the photosphere of the more luminous primary star are given. The H-alpha features consists of a P Cygni component that shares the motion of the primary, and which probably originates at the base of its wind, and a broad, stationary emission component. It is proposed that the broad emission forms in a plane midway between the stars where the winds collide. A simple geometric model is used to show that this placement of the broad component can explain the lack of orbital velocity shifts, the near-constancy of the emission strength throughout the orbit, the large velocities associated with the H-alpha wings, and the constancy of the velocity range observed.

Wiggs, Michael S.↗
DOE OSTI2022

Characterizing particle-based thermal storage performance using optical methods for use in next generation concentrating solar power plants

Concentrating Solar Power (CSP) generation is an attractive option for low-emission power generation; however, the high costs of thermal storage associated with concentrating solar create a large barrier for their use and adaptation into modern life. Lowering their operation costs, while maintaining high thermal storage and transfer performance is essential. Solid particle-based heat exchange systems can reduce CSP cost but are often less efficient. Efforts to increase their performance have led to use of binary size particle mixes. Presented is an optical-based thermal analysis technique used to measure near-wall thermal conductivity of particle beds essential in determining their heat exchanger efficiency. Modulated Photothermal Radiometry is used to make dynamic temperature measurements, allowing for the extraction of the most relevant thermal properties like thermal conductivity, specific heat, and effusivity. The system uses a modulated laser source causing a damped periodic heat flux, resulting in a frequency and thermal property dependent surface temperature, of which is measured using radiometry. Lock-In techniques are used to extrapolate the amplitude of the signal. Plotting the amplitude against the root angular frequency allows for effusivity measurement by ratio to a known sample. Using specific heat measurements from literature and density measurements, the thermal conductivity of the particle mixes can be calculated. The simplicity of MPTR to probe through the depth of the bed is ideal for use in CSP for dynamic thermal performance monitoring.

Corona, Javier↗
NASA NTRS2000

Spectral and Timing Investigations of Dwarf Novae Selected in Hard X-Rays

There are 9 dwarf novae (DN) among the 43 cataclysmic variables (accreting white dwarfs in close binary systems) that were detected during the HEAO-1 all-sky X-ray survey (1977-1979). On the other hand, there are roughly one hundred dwarf novae that are closer and/or optically brighter and yet they were not detected as hard X-ray sources. Two of the HEAO-1 DN show evidence for X-ray pulsations that imply strong magnetic fields on the white dwarf surface, and magnetic CVs are known to be strong X-ray sources. However, substantial flux in hard X-rays may be caused by non-magnetic effects, such as an optically thin boundary layer near a massive white dwarf. We proposed RXTE observations to measure plasma temperatures and to search for X-ray pulsations. The observations would distinguish whether these DN belong to one of (rare) magnetic subclasses. For those that do not show pulsations, the observations support efforts to define empirical relations between X-ray temperature, the accretion rate, and the mass of the white dwarf. The latter is determined via optical studies of the dynamics of the binary constituents.

Thorstensen, John↗
DOE OSTI2013

THE QUADRUPLE PRE-MAIN-SEQUENCE SYSTEM LkCa 3: IMPLICATIONS FOR STELLAR EVOLUTION MODELS

We report the discovery that the pre-main-sequence (PMS) object LkCa 3 in the Taurus-Auriga star-forming region is a hierarchical quadruple system of M stars. It was previously known to be a close ({approx}0.''5) visual pair, with one component being a moderately eccentric 12.94 day single-lined spectroscopic binary. A re-analysis of archival optical spectra complemented by new near-infrared (NIR) spectroscopy shows both visual components to be double lined; the second one has a period of 4.06 days and a circular orbit. In addition to the orbital elements, we determine optical and NIR flux ratios, effective temperatures, and projected rotational velocities for all four stars. Using existing photometric monitoring observations of the system that had previously revealed the rotational period of the primary in the longer-period binary, we also detect the rotational signal of the primary in the 4.06 day binary, which is synchronized with the orbital motion. With only the assumption of coevality, a comparison of all of these constraints with current stellar evolution models from the Dartmouth series points to an age of 1.4 Myr and a distance of 133 pc, consistent with previous estimates for the region and suggesting that the system is on the near side of the Taurus complex. Similar comparisons of the properties of LkCa 3 and the well-known quadruple PMS system GG Tau with the widely used models from the Lyon series for a mixing length parameter of {alpha}{sub ML} = 1.0 strongly favor the Dartmouth models.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2012

VERY LARGE TELESCOPE/X-SHOOTER SPECTROSCOPY OF THE CANDIDATE BLACK HOLE X-RAY BINARY MAXI J1659-152 IN OUTBURST

We present the optical to near-infrared spectrum of MAXI J1659-152 during the onset of its 2010 X-ray outburst. The spectrum was obtained with X-shooter on the ESO Very Large Telescope early in the outburst simultaneous with high-quality observations at both shorter and longer wavelengths. At the time of the observations, the source was in the low-hard state. The X-shooter spectrum includes many broad ({approx}2000 km s{sup -1}), double-peaked emission profiles of H, He I, and He II, characteristic signatures of a low-mass X-ray binary during outburst. We detect no spectral signatures of the low-mass companion star. The strength of the diffuse interstellar bands results in a lower limit to the total interstellar extinction of A{sub V} {approx_equal} 0.4 mag. Using the neutral hydrogen column density obtained from the X-ray spectrum we estimate A{sub V} {approx_equal} 1 mag. The radial velocity structure of the interstellar Na I D and Ca II H and K lines results in a lower limit to the distance of {approx}4 {+-} 1 kpc, consistent with previous estimates. With this distance and A{sub V} , the dereddened spectral energy distribution represents a flat disk spectrum. The two 10 minute X-shooter spectra show significant variability in the red wing of the emission-line profiles, indicating a global change in the density structure of the disk, though on a timescale much shorter than the typical viscous timescale of the disk.

79 ASTRONOMY AND ASTROPHYSICS↗