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NASA NTRS1974

Binary stellar winds

Stellar winds from a binary star pair will interact with each other along a contact discontinuity. We discuss qualitatively the geometry of the flow and field resulting from this interaction in the simplest case where the stars and winds are identical. We consider the shape of the critical surface (defined as the surface where the flow speed is equal to the sound speed) as a function of stellar separation and the role of shock waves in the flow field. The effect of stellar spin and magnetic sectors on the field configuration is given. The relative roles of mass loss and magnetic torque in the evolution of orbital parameters is discussed.

Siscoe, G. L.↗

NASA NTRS1975

The HEAO A-2 experiment on the spatial and spectral structure of the X-ray sky /0.2-60 keV/

The HEAO A-2 experiment is described which is designed to observe the spectral and spatial structure of cosmic X-radiation over the entire sky with the minimum sensitivity and cross checks required to achieve a number of objectives. Developments in X-ray astronomy are discussed which are relevant to the experiment, including setting a lower limit on the number of discrete sources contributing to the background flux, determining the spatial dependence of the flux, observations of the spectral components of discrete sources, and the study of X-ray absorption by interstellar gas and the atmospheres of binary stars associated with pulsating X-ray sources. It is shown that systematics-free measurements will be made by making simultaneous observations of single sources with several detectors, by using two-layer detectors to eliminate the effects of electron contamination, and by incorporating magnets into low-energy detectors to minimize electron contamination.

Boldt, E.↗

NASA NTRS1975

Upper mass limits for stable rotating white dwarfs

Models of nonmagnetic axisymmetric differentially rotating zero-temperature white dwarfs are constructed and tested for stability. Upper mass limits, beyond which models become secularly and dynamically unstable to growth of nonaxisymmetric perturbations, are found at 2.5 solar masses and 4.6 solar masses, respectively. The upper mass limit for secular stability is practically the same for the two angular momentum distributions considered. Crude growth rates due to gravitational radiation and degenerate-electron viscosity are calculated for the secularly unstable models. Except for a narrow parameter range, gravitational radiation is the dominant destabilizing mechanism. For masses between 3.5 and 4.6 solar masses, the secular instability grows on a time scale of about 10 to 1000 years; for masses exceeding about 4.6 solar masses, the dynamic instability grows on a time scale of seconds. Implications of these results for mass-transfer binary star systems and degenerate stellar cores are discussed.

Durisen, R. H.↗

NASA NTRS1975

Eclipses by an elliptical torus

A general procedure for computing the effects of eclipses by a torus, including both the outer horizon and the inner or hole horizon, was developed. The procedure can be used for any of the simple figures of revolution encountered in binary-star models. That is, the thickness can be made negligible to produce a thin ring, the hole radius can be set to zero to yield a thin disk, the radius to the center of the elliptical meridian section can be brought to zero to give an ellipsoid of revolution, or the equatorial axis of the elliptical meridian section can be made to equal zero to produce a section of a right circular cylinder.

Wilson, R. E.↗

NASA NTRS1977

Recognition of compact astrophysical objects

NASA's Laboratory for High Energy Astrophysics and the Dept. of Physics and Astrophysics at the Univ. of Md. collaberated on a graduate level course with this title. This publication is an edited version of notes used as the course text. Topics include stellar evolution, pulsars, binary stars, X-ray signatures, gamma ray sources, and temporal analysis of X-ray data.

Ogelman, H.↗

NASA NTRS1977

Time scale for the formation of the earth and planets and its role in their geochemical evolution

The initial mass of the solar nebula is discussed. Models of a massive nebula (two solar masses and more) encounter serious difficulties: an effective mechanism of transfer of the momentum from the central part of the nebula outward, capable of leading to formation of the sun and removal of half the mass of the nebula from the solar system has not been found. As a consequence of the instability of these models, their evolution can end with the formation, not a planetary system, but of a binary star. The possibility is demonstrated of obtaining acceptable growth rates for Uranus and Neptune by prolonging the thickening of preplanetary dust in the region of large masses. The important role of large bodies in the process of formation of the planets is noted. The impacts of such bodies, moving in heliocentric orbits, could have imparted considerable additional energy to the forming Moon, which, together with the energy given off by the joining of a small number of large protomoons, could have led to a high initial temperature of the moon.

Safronov, V. S.↗

NASA NTRS1977

Cloud physics laboratory project science and applications working group

The conditions of the expansion chamber under zero gravity environment were simulated. The following three branches of fluid mechanics simulation under low gravity environment were accomplished: (1) oscillation of the water droplet which characterizes the nuclear oscillation in nuclear physics, bubble oscillation of two phase flow in chemical engineering, and water drop oscillation in meteorology; (2) rotation of the droplet which characterizes nuclear fission in nuclear physics, formation of binary stars and rotating stars in astrophysics, and breakup of the water droplet in meteorology; and (3) collision and coalescence of the water droplets which characterizes nuclear fusion in nuclear physics and processes of rain formation in meteorology.

Hung, R. J.↗

NASA NTRS1978

Spectroscopy of the extreme-ultraviolet source Feige 24 - The binary orbit and the mass of the white dwarf

Results are reported for coude spectroscopy of the extreme-ultraviolet white dwarf Feige 24. Radial velocities of the H-alpha, He I 5876-A, and He I 6678-A emission lines, and the underlying M-dwarf absorption features, were determined from spectrograms obtained with the Lick 3-m telescope. The velocities show a binary period of 4.239(+ or - 0.0015) days. The emission-line and absorption-line velocities agree in phase, which indicates that the emission lines originate in the atmosphere of the M-dwarf secondary as a result of reprocessing of the EUV radiation. This effect is modeled, and the observed amplitude of the emission-line variability is used to place a lower limit on the orbital inclination. From these and other data it is shown that the mass of the white dwarf lies between 0.46 and 1.24 solar masses. Some possible implications for the evolution of binary stars are briefly discussed.

Thorstensen, J. R.↗

NASA NTRS1978

A search for optical pulsations from GX 1+4 at H-alpha

H-alpha observations of the binary-star candidate for the slowly pulsating hard X-ray source GX 1+4 are reported which were undertaken to search for pulsations in the H-alpha flux that are synchronous with the X-ray period of about 2 min. No significant periodic variation of the candidate star was detected in the frequency band searched. Three-sigma upper limits of 1.7% (sinusoidal pulse shape) and 0.7% (X-ray pulse shape) are set for the pulsed fraction of the H-alpha flux. It is noted that because of possible diffusion from a cloud that is optically thick to Balmer radiation, the observed lack of pulsations in the H-alpha flux need not compromise the identification of GX 1+4 with the candidate star.

Krzeminski, W.↗

NASA NTRS1979

The optical counterpart of GX 339-4, a possible black hole X-ray source

Optical studies of the galactic X-ray source GX 339-4 (4U 1658-48), which led to its recent identification as reported by Doxsey et al. (1979), are presented. Reddening and distance estimates are given, as well as evidence for optical variability on differing time scales. The emission-line spectra and UBV photometry suggest that GX 339-4 may be at about 8 kpc and have a main-sequence B star binary companion. Both the optical spectrum and optical/X-ray luminosity ratio for GX 339-4 may be similar to Cir X-1.

Grindlay, J. E.↗

NASA NTRS1980

An Assessment of Ground-Based Techniques for Detecting Other Planetary Systems. Volume 2: Position papers

The capabilities of several astronomical interferomenter system concepts are assessed and the effects of the Earth's atmosphere on astrometric precision are examined in detail. Included is an examination of the use of small aperture interferometry to detect planets in binary star systems. It is estimated that, for differential astrometric observation, an amplitude interferometer having two separate telescopes should permit observations of stars as faint as 14th magnitude and a positional accuracy of 0.00005 arc-sec. Instrumental, atmospheric, and photon noise errors that apply to interferometric observation are examined. It is suggested that the effects of atmospheric turbulence may be eliminated with the use of two color refractometer systems. Several sites for future telescopes dedicated to the search for planetary systems are identified.

Black, D. C.↗

NASA NTRS1980

Ultraviolet spectroscopy of binary systems

Four typical binary systems that illustrate some of the major problems in the study of binary stars are discussed. Consideration is given to (1) high-luminosity X-ray sources typified by Cyg X-1 (HDE 226868) and Vela XR-1 (HD 77581), (2) low-luminosity X-ray sources (HZ Her), (3) late-type systems of W UMa and RS CVn type, and (4) cool supergiants with a hot companion (VV Cephei).

Dupree, A. K.↗

NASA NTRS1980

Design aspects of a laser gravitational wave detector in space

Certain optical and mechanical aspects of a proposed laser gravitational wave antenna in space are briefly discussed. The proposed concept consists of a free-mass antenna with the test masses separated by a distance of 1,000,000 km. A laser heterodyne technique is employed to measure the distance change between test masses resulting from gravitational wave interaction. The proposed scheme is considered to offer the necessary sensitivity to detect gravitational radiation from binary stars predicted by General Relativity Theory.

Decher, R.↗

NASA NTRS1981

The ultraviolet spectrum of the twin-degenerate interacting binary G61-29

A low-resolution IUE spectrum (1200 A-1900 A) of the twin-degenerate white-dwarf binary star G61-29 is presented. A comparison is made to similar IUE spectra of the old novae DQ Her and V603 Aql. G61-29 shows N V 1240 A and He II 1640 A in emission. Unlike the old novae, the C IV 1550 A doublet is not present. It is proposed that the mass-losing He white dwarf (with a mass of 0.02 solar mass) is the H-exhausted, He-rich core of an old star in which the original CNO nuclei have been converted to N-14 by the CNO-cycles.

Lambert, D. L.↗

NASA NTRS1982

The chromospheric rotation activity relation in late type close binary systems

The IUE data on 36 late type close binary stars are presented. It is shown that the chromospheric and TR line fluxes increase with decreasing stellar rotation period, though not as rapidly as does the X-ray flux. There is an increasing dependence upon rotation with increasing line temperature. The data are consistent with the hypothesis that there exists a critical rotation rate, which depends on temperature, below which the emission flux is independent of rotation and above which it increases linearly with increasing angular velocity omega.

Walter, F. M.↗

NASA NTRS1982

Discovery of 69 ms periodic X-ray pulsations in A0538-66

The detection of X ray pulsations with a period of 69.2126 ms from A0538-66 was done from the Einstein Observatory. A point source was located by the High Resolution Imager and a proportional counter registered a flux of 40 counts/sec over background. A column spectral density of 2 x 10 to the 23/sq cm identified the object as A0538-66. A persistent periodicity of 0.0692126 sec was observed throughout the event. The outbursts were not detected on three other observations of A0538-66, and a best fit to a change of rotation velocity indicated that the period observed was from a binary star with a Doppler shifted signal. The two stars are separated by less than 39 solar radii, with the larger star having a 40 solar radius. Consideration is given to the possibility that the X rays are due to accretion on a neutron star and that the two stars at times share a common envelope.

Skinner, G. K.↗

NASA NTRS1982

UV eclipse observations of CI Cyg

Low spectral resolution observations were obtained with the IUE during the eclipse phase. Additional data obtained by other IUE groups have been included in the eclipse observations, making it possible to examine the UV spectral properties of CI Cyg over nearly an entire orbit which spans early 1979 through mid 1981. Data obtained over this period suggest an overall decline in UV emission, consistent with the decline of optical emission following the outburst of 1975. The short-wavelength spectrum 1200-2000 A is characterized by numerous intense high-excitation emission lines which become more prominent out of eclipse. The LWR wavelength range 2000-3200 A exhibits a few more additional lines of O III, Mg II, and He II which are superimposed on continuum that rises gradually with increasing wavelength. The observations are consistent with a binary star model which involves mass transfer from the extended cool envelope of the primary to the compact secondary.

Michalitsianos, A. G.↗

NASA NTRS1982

X-ray properties of the Be/X-ray systems 2S0114+650 = LSI+65 deg 010

Results are presented from experiments on the Einstein Observatory, HEAO-1 and OSO-8 on the temporal and spectral properties of 2S0114+650. In a 12 hour Einstein MPC and SSS observation two episodes of flaring occurred by an order of magnitude over about 1 hour. Variability on shorter time scales showed a preferred period of 14.9 minutes, but periodic pulsations were not seen in the HEAO-1 and OSO-8 data. There is some evidence that the spectrum is steeper when the source is quiescent at low luminosity, but no large spectral changes attended the flares. Absorption column densities were consistent with interstellar reddening of the proposed companion, the Be star LSI+65 deg 010. In the minute and hour variability and in the spectral character, 2S0114+650 is similar to other Be star-neutron star binary X-ray sources. Variations over several days in the OSO-8 data suggest orbital effects.

Koenigsberger, G.↗