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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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NASA NTRS1992

Dynamics of binary and planetary-system interaction with disks - Eccentricity changes

Protostellar and protoplanetary systems, as well as merging galactic nuclei, often interact tidally and resonantly with the astrophysical disks via gravity. Underlying our understanding of the formation processes of stars, planets, and some galaxies is a dynamical theory of such interactions. Its main goals are to determine the geometry of the binary-disk system and, through the torque calculations, the rate of change of orbital elements of the components. We present some recent developments in this field concentrating on eccentricity driving mechanisms in protoplanetary and protobinary systems. In those two types of systems the result of the interaction is opposite. A small body embedded in a disk suffers a decrease of orbital eccentricity, whereas newly formed binary stars surrounded by protostellar disks may undergo a significant orbital evolution increasing their eccentricities.

Atrymowicz, Pawel↗
NASA NTRS1992

Populations of low-mass black hole binaries

The evolution of a population of massive binaries with low-mass secondaries is considered by contrasting the fate of black hole-producing systems with those leaving neutron stars. It is found that the interacting black hole binaries may be even more common than the familiar neutron star LMXBs. Certain unusual expected systems are described, and a comparison with present observations is made to determine the accuracy of predictions of this scenario.

Romani, Roger W.↗
NASA NTRS1992

Tidal interactions of inspiraling compact binaries

We discuss the tidal interaction in neutron star-neutron star and neutron star-black hole binaries and argue that they will not be tidally locked during the gravitational inspiral. More specifically, we show that, for inspiraling neutron stars of mass greater than about 1.2 solar mass, the shortest possible tidal synchronization time exceeds the gravitational decay time, so that the neutron star cannot be tidally locked prior to tidal disruption, regardless of its internal viscosity. For smaller mass neutron stars, an implausibly large kinematic viscosity - nearly the speed of light times the stellar radius - is required for tidal locking. We also argue that the mass transfer which occurs when the neutron star reaches the tidal radius will be unstable in neutron star-black hole binaries, and the instability will destroy the neutron star in a few orbital periods. The implications of our work for the detection of these sources by LIGO and other gravitational wave observatories and for the gamma-ray burst scenarios of Paczynski (1986, 1991) are discussed.

Bildsten, Lars↗
NASA NTRS1992

The infrared counterpart of the eclipsing X-ray binary HO253 + 193

We report the identification of the infrared counterpart of the pulsating X-ray source HO253 + 193. It is a highly reddened star varying in K light with a period near 3 hr, but an apparent even-odd effect in the light curve implies that the true period is 6.06 hr. Together with the recent report of X-ray eclipses at the latter period, this establishes the close binary nature of the source. Infrared minimum occurs at X-ray minimum, certifying that the infrared variability arises from the tidal distortion of the lobe-filling secondary. The absence of a point source at radio wavelengths, plus the distance derived from the infrared data, suggests that the binary system is accidentally located behind the dense core of the molecular cloud Lynds 1457. The eclipses and pulsations in the X-ray light curve, coupled with the hard X-ray spectrum and low luminosity, demonstrate that HO253 + 193 contains an accreting magnetic white dwarf, and hence belongs to the 'DQ Herculis' class of cataclysmic variables.

Zuckerman, B.↗
NASA NTRS1992

Terrain tracking for lander guidance using binary phase-only spatial filters

We demonstrate the use of binary phase-only spatial filters (BPOFs) for tracking target sites through a sequence of gray-scale terrain images. The filters are demonstrated in a closed loop guidance system for a laboratory lander mockup. Images of a 3D terrain board taken by the lander's video camera are preprocessed to produce binary intensity contour maps of a simulated planetary surface. A BPOF is made from a section of the current preprocessed image centered on the exact desired landing site. After the lander has descended to a lower altitude, the BPOF is correlated with a new image. The position of the correlation peak is used in making the next filter and to guide the lander so as to recenter the landing site in the camera's view. We present testbed results of the accuracy with which a site may be tracted from orbit to landing, and the maximum scale, translation, and rotation which can be tolerated between subsequent images. Application of the results to NASA's proposed Mars Rover Sample Return (MRSR) and Mars Environmental Survey (MESUR) missions is discussed.

Reid, Max B.↗
NASA NTRS1993

Hydrodynamic instability and coalescence of close binary systems

The meaning of hydrodynamic instability of close binary systems is clarified, and the resulting large (but finite) value of the radial infall velocity near the end of the coalescence is estimated. Emphasis is placed on the case where the orbital decay is driven by gravitational radiation. A simple calculation of the orbital decay is presented for a simple generic model of a close binary.

Lai, Dong↗
NASA NTRS1993

RE 1016-053 - A pre-cataclysmic binary, and the first extreme ultraviolet and X-ray detections of a DAO white dwarf

Photometric observations and analysis of the optical, UV, EUV, and X-ray spectra are presented for the EUV/X-ray source RE 1016-53. Multiwavelength observations of RE 1016-53 point out that it is a precataclysmic binary. Optical spectra exhibit the steep blue continuum and Balmer absorption typical of a hot white dwarf, but there are bright, narrow emission lines of H I, He I, and Ca II superimposed on this. The white dwarf component, with T (eff) = 55,800 +/- 1000 K and log g = 7.81 +/- 0.007, dominates the spectrum from the optical to the EUV/X-ray. An He II 4686 A absorption line suggests that the white dwarf is a hydrogen-helium (DAO) hybrid star. Four of the five precataclysmic binaries with white dwarfs with T(eff) greater than 40,000 K appear to be DAOs. A mass of 0.57 +/- 0.003 solar mass has been derived.

Tweedy, R. W.↗
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 NTRS1993

Case study of binary and ternary synthetic discriminant function filters with similar in-class and out-of-class images

A simulation study is reported of the performance of two designs of ternary synthetic discriminant function (SDF) filters. The filters are compared to binary SDFs in terms of the probability of correct identification P(ID) between in-class and out-of-class image sets. Compared to binary synthetic discriminant function (BSDF) filters, both ternary SDF filters designs offer improved performance in P(ID) and thus allow extension of the maximum filter direction range when evaluated in the presence of white image noise. Larger distortion range filters translate to fewer correlations required to perform image identification, and thus higher system speed. The TSDF(SNR) filters had the highest of system performance, while TSDF(d) filters were able to improve discrimination to a degree, but their optimal designs had essentially the same SNR performance as the BSDF filters.

Downie, John D.↗
NASA NTRS1992

Low-mass X-ray binaries and gamma-ray bursts

More than twenty years after their discovery, the nature of gamma-ray burst sources (GRBs) remains mysterious. The results from BATSE experiment aboard the Compton Observatory show however that most of the sources of gamma-ray bursts cannot be distributed in the galactic disc. The possibility that a small fraction of sites of gamma-ray bursts is of galactic disc origin cannot however be excluded. We point out that large numbers of neutron-star binaries with orbital periods of 10 hr and M dwarf companions of mass 0.2-0.3 solar mass are a natural result of the evolution of low-mass X-ray binaries (LMXBs). The numbers and physical properties of these systems suggest that some gamma-ray burst sources may be identified with this endpoint of LMXB evolution. We suggest an observational test of this hypothesis.

Lasota, J. P.↗
NASA NTRS1993

The last three minutes - Issues in gravitational-wave measurements of coalescing compact binaries

Gravitational-wave interferometers are expected to monitor the last three minutes of inspiral and final coalescence of neutron star and black hole binaries at distances approaching cosmological, where the event rate may be many per year. Because the binary's accumulated orbital phase can be measured to a fractional accuracy much lower than 10 exp -3, and relativistic effects are large, the wave forms will be far more complex and carry more information than has been expected. Improved wave form modeling is needed as a foundation for extracting the waves' information, but is not necessary for wave detection.

Cutler, Curt↗
NASA NTRS1991

Planetary lander guidance using binary phase-only filters

We demonstrate the use of binary phase-only filters (BPOFs) in a closed loop guidance system for a laboratory lander mockup. Images of a 3-D terrain board taken by the lander's video camera are preprocessed to produce 128 x 128 binary intensity contour maps of the simulated planetary surface. A BPOF is made from a section of the current preprocessed image centered on the exact desired landing site. After the lander has descended to a lower altitude, the BPOF is correlated with a new image. The position of the correlation peak is used in making the next filter and to guide the lander so as to recenter the landing site in the camera's view. We present results of the accuracy with which a site may be tracked from orbit to landing, and the maximum scale, translation, and rotation which can be tolerated between subsequent images. The tolerable scale distortion is quite critical, as it determines the maximum filter update time available at a given descent rate. Application of the results to NASA's proposed Mars Rover Sample Return (MRSR) and Mars Environmental Survey (MESUR) missions is discussed. In both cases, electronic implementations of the algorithm may be sufficient to provide the required guidance system performance.

Reid, Max B.↗
NASA NTRS1993

Stability of outer planetary orbits around binary stars - A comparison of Hill's and Laplace's stability criteria

A comparison is made between the stability criteria of Hill and that of Laplace to determine the stability of outer planetary orbits encircling binary stars. The restricted, analytically determined results of Hill's method by Szebehely and coworkers and the general, numerically integrated results of Laplace's method by Graziani and Black (1981) are compared for varying values of the mass parameter mu. For mu = 0 to 0.15, the closest orbit (lower limit of radius) an outer planet in a binary system can have and still remain stable is determined by Hill's stability criterion. For mu greater than 0.15, the critical radius is determined by Laplace's stability criterion. It appears that the Graziani-Black stability criterion describes the critical orbit within a few percent for all values of mu.

Kubala, A.↗
NASA NTRS1991

A model of the evaporation of binary-fuel clusters of drops

A formulation has been developed to describe the evaporation of dense or dilute clusters of binary-fuel drops. The binary fuel is assumed to be made of a solute and a solvent whose volatility is much lower than that of the solute. Convective flow effects, inducing a circulatory motion inside the drops, are taken into account, as well as turbulence external to the cluster volume. Results obtained with this model show that, similar to the conclusions for single isolated drops, the evaporation of the volatile is controlled by liquid mass diffusion when the cluster is dilute. In contrast, when the cluster is dense, the evaporation of the volatile is controlled by surface layer stripping, that is, by the regression rate of the drop, which is in fact controlled by the evaporation rate of the solvent. These conclusions are in agreement with existing experimental observations. Parametric studies show that these conclusions remain valid with changes in ambient temperature, initial slip velocity between drops and gas, initial drop size, initial cluster size, initial liquid mass fraction of the solute, and various combinations of solvent and solute. The implications of these results for computationally intensive combustor calculations are discussed.

Harstad, K.↗
NASA NTRS1993

Scattering from binary optics

There are a number of sources of scattering in binary optics: etch depth errors, line edge errors, quantization errors, roughness, and the binary approximation to the ideal surface. These sources of scattering can be systematic (deterministic) or random. In this paper, scattering formulas for both systematic and random errors are derived using Fourier optics. These formulas can be used to explain the results of scattering measurements and computer simulations.

Ricks, Douglas W.↗
NASA NTRS1993

Low cost paths to binary optics

Application of binary optics has been limited to a few major laboratories because of the limited availability of fabrication facilities such as e-beam machines and the lack of standardized design software. Foster-Miller has attempted to identify low cost approaches to medium-resolution binary optics using readily available computer and fabrication tools, primarily for the use of students and experimenters in optical computing. An early version of our system, MacBEEP, made use of an optimized laser film recorder from the commercial typesetting industry with 10 micron resolution. This report is an update on our current efforts to design and build a second generation MacBEEP, which aims at 1 micron resolution and multiple phase levels. Trails included a low cost scanning electron microscope in microlithography mode, and alternative laser inscribers or photomask generators. Our current software approach is based on Mathematica and PostScript compatibility.

Nelson, Arthur↗
NASA NTRS1993

Accretion disks in low-mass X-ray binaries

In this paper we review recent developments in our knowledge of accretion disks in low-mass X-ray binaries (LMXBs). We discuss some common behavior between the disks in cataclysmic variables and LMXBs, especially among those systems with high mass ratios. We consider ellipsoidal variability of soft X-ray transients (SXTs: transient LMXBs) in quiescence, and discuss the evidence for transient disk contamination of the light curves of these objects. We then show how optical photometry of SXTs in both outburst and quiescence can place useful constraints on the mass of the compact object in these binaries. Finally we present new results on the accretion disk structures of AC 211 in M15 and X 1916-05. We show that considerable evidence now exists for sizable disk structure displaced about 180 deg from the secondary: the origin of this structure is as yet unknown.

Callanan, Paul J.↗
NASA NTRS1994

Emission lines from X-ray-heated accretion disks in low-mass X-ray binaries

We investigate the structure of accretion disks illuminated by X-rays from a central compact object in a binary system. X-rays can photoionize the upper atmosphere of the disk and form an accretion disk corona (ADC) where emission lines can form. We construct a model to calculate the vertical structure and the emission spectrum of the ADC with parameters appropriate to low-mass X-ray binaries. These models are made by nonlocal thermodynamic equilibrium calculations of ion and level populations and include a large number of atomic processes for 10 cosmically abundant elements. Transfer of radiation is treated by using the escape probability formalism. The vertical temperature profile of the ADC consists of a Compton-heated region and a mid-T zone where the temperature is approximately 10(exp 6) K. A thermal instability occurs close to the disk photosphere and causes the temperature of the ADC to drop abruptly from 10(exp 6) K to several times 10(exp 4) K. The emission spectrum in the optical, ultraviolet, extreme ultraviolet, and X-ray range is discussed and compared with the observations.

Ko, Yuan-Kuen↗