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Huang, S.-S.

Publications and source records attributed to Huang, S.-S..

At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1978

Interpretation of Beta Lyrae. IV - Hydrogen emission profiles and the pattern of gaseous flow in the system

The paper presents an interpretation of hydrogen emission profiles found in Beta Lyrae by attributing the asymmetry of the two emission peaks of both H-alpha and H-gamma at different phases to the absorption of an expanding-rotating gaseous stream. It is proposed that different relative shifts of the absorption line with respect to the emission line exist at different phases resulting in an apparent change in the profile with phase. Based on this idea, the expected profiles at four different phases have been computed for the H-alpha and H-gamma lines. They show a general trend close to what has been observed. Based on this same idea an apparent discrepancy between the observed results of the H-gamma profile obtained at two different epochs about 15 years apart becomes understandable. Finally a physical picture that can produce this periodic shift of the emission line relative to the absorption line is proposed and discussed.

Huang, S.-S.↗
NASA NTRS1978

Orbital changes of the gaseous ring around Be stars. II - Apsidal motion and slow drift of the orbital elements

It is shown that the observed data about the apsidal motion of gaseous rings around some Be stars, like Beta(1) Mon and Pi Aqr, cannot be explained solely by the influence of the equatorial bulge. This fact has prompted the development of a theory of apsidal motion and slow drift of orbital elements that is based on the mixing of slowly escaping gases from the central star with gases in the emission ring around it. Thus, the basic physical idea in this paper follows closely what has been advanced in the first paper of this series but the mathematical treatment has been broadened in order to deal with the actual orbits, instead of osculating orbits, of particles in the ring. In accordance with this theory, it is believed that in cases where no mixing of gases takes place, the apsidal motion is controlled solely by the equatorial bulge. But in cases where mixing takes place, the apsidal motion depends upon the manner of gas mixing as well.

Huang, S.-S.↗
NASA NTRS1977

Interpretation of Beta Lyrae. III - A study of the disk around the secondary component

Light curves of Beta Lyrae available in the far-ultraviolet, visual, and infrared regions of the spectrum at numerous phases in eclipse are analyzed in order to investigate the physical and radiative nature of the disk surrounding the secondary component. The results of this analysis together with those of other investigators lead to the proposal that the outer regions of the disk are dominated by free electrons. This electron-scattering envelope is most likely the source of infrared radiation as well as the cause of the observed polarization. However, the radiation in the region from the optical to the far-ultraviolet comes mainly from submerged layers where local thermodynamic equilibrium prevails. These layers represent the photosphere of either the disk or the secondary component itself.

Brown, D. A.↗
NASA NTRS1977

Orbital changes of the gaseous ring around Be stars

In order to understand the seemingly erratic V/R variations and radial velocity curves of emission edges and central absorption of some Be stars, we have advanced, for the changes of structure of the gaseous ring around these stars, a theory that is based on the interaction between the existing ring and the newly ejected matter from the star. It shows that the structural change of the ring is completely controlled by the angular-momentum input factor and the dissipation factor. In light of this understanding, we have gone on to interpret the observed results of Beta-1 Mon and Pi Aqr.

Huang, S.-S.↗
NASA NTRS1976

A theory of ring formation around Be stars

A theory for the formation of gaseous rings around Be stars is developed which involves the combined effect of stellar rotation and radiation pressure. A qualitative scenario of ring formation is outlined in which the envelope formed about a star from ejected material is in the form of a disk in the equatorial plane, collisions between ejected gas blobs are inevitable, and particles with high angular momenta form a rotating ring around the star. A quantitative description of this process is then formulated by considering the angular momentum and dynamical energy of the ejected matter as well as those of the ring alone, without introducing any other assumptions.

Huang, S.-S.↗
NASA NTRS1976

An elementary theory of eclipsing depths of the light curve and its application to Beta Lyrae

An elementary theory of the ratio of depths of secondary and primary eclipses of a light curve has been proposed for studying the nature of component stars. It has been applied to light curves of Beta Lyrae in the visual, blue, and far-ultraviolet regions with the purpose of investigating the energy sources for the luminosity of the disk surrounding the secondary component and determining the dominant radiative process in the disk. No trace of the spectrum of primary radiation has been found in the disk. Therefore, it is suggested that LTE is the main radiative process in the disk, which radiates at a temperature of approximately 12,000 K in the portion that undergoes eclipse. A small source corresponding to 14,500 K has also been tentatively detected and may represent a hot spot caused by hydrodynamic flow of matter from the primary component to the disk.

Huang, S.-S.↗
NASA NTRS1975

Interpretation of BM Orionis

The entire light curve of the BM Ori system both inside and outside primary and secondary eclipses has been examined on the basis of two models for the disk around the secondary component: one with the luminous energy of the disk coming entirely from the secondary, and another with the luminous energy coming at least partly from the primary. It has been found that if the disk is highly opaque, as is suggested by the fitting of the light curve, there exist in the first model discrepancies between what has been derived from the luminosity consideration for the secondary component and what has been derived from the radius consideration. Hence the second model is accepted. Based on this model the nature of both component stars has been examined from a consideration of the luminosity and the dimensions of the disk.

Huang, S.-S.↗
NASA NTRS1974

Profiles of emission lines in Be stars. III

The long-period V/R emission variations in three Be stars, HD 20336, 25 Ori, and beta-one Mon have been studied according to the mathematical formulation of the eccentric rotating model presented in a previous paper. The predictions of the theory fit satisfactorily the general trend of observed data. Periods, eccentricities, and sizes of the emitting ring with respect to the stellar radius are thereby derived and found to be consistent with results of the previous investigation of 105 Tauri.

Albert, E.↗
NASA NTRS1974

Interpretation of epsilon Aurigae. III

The light curve expected from the eclipse of a star by a companion possessing a semitransparent disk has been investigated. Two computational procedures for deriving the light curve based on the geometrically thin-disk model are given here. Using these procedures, we have calculated the light curves of epsilon Aur based on different sets of parameters including those given previously by Wilson. We have also studied the light curve of epsilon Aur based on a geometrically thick disk model, and have advanced two proposals in order to understand the change in the shape of the light curve from one eclipse to the next, namely, (1) the rapid evolution that occurs in the disk and (2) the density waves in the disk and/or individual condensations that are revolving around the secondary each in an independent way.

Huang, S.-S.↗
NASA NTRS1974

Interpretation of epsilon Aurigae. II - Infrared excess, secondary light variations, and plausible formation of a planetary system

Infrared excess based on the disk model proposed in a previous paper was computed. It was found that the disk alone will emit infrared radiation below the margin of detection. However, if individual condensations are present, the combined result of the disk proper and the condensations yields results of infrared excesses that are consistent with observations. The presence of condensations also makes the secondary light variation understandable. An elementary theory is developed that analyzes such light variations. The result of the analysis yields the size of the orbit of the condensation around the secondary component.

Huang, S.-S.↗
NASA NTRS1973

Profiles of emission lines in Be stars. II - Interpretation of the long-period V/R variation.

Investigation of the long-period V/R variation in some Be stars studied by McLaughlin (1966) and others, based on the assumption that the variation is caused by the apsidal motion of an elliptical ring in which the emitting atoms revolve around the star according to Kepler's laws of motion. The results indicate that the behavior of the V/R variation depends upon both the eccentricity and the lateral extent of the gaseous ring. However, if the ring is narrower than a certain limit, the dependence on the width is negligible. In such a case, the eccentricity of the ring can be determined by the observed amplitude of the V/R variation. Based on this model, the radial-velocity curves of both emission edges and central absorption are derived. It is found that they all have the same amplitude, which also depends on the eccentricity, and that all are changing in phase with the V/R variation.

Huang, S.-S.↗
NASA NTRS1973

Extrasolar planetary systems.

The terms 'planet' and 'planet-like objects' are defined. The observational search for extrasolar planetary systems is described, as performable by earthbound optical telescopes, by space probes, by long baseline radio interferometry, and finally by inference from the reception of signals sent by intelligent beings in other worlds. It is shown that any planetary system must be preceded by a rotating disk of gas and dust around a central mass. A brief review of the theories of the formation of the solar system is given, along with a proposed scheme for classification of these theories. The evidence for magnetic activity in the early stages of stellar evolution is presented. The magnetic braking theories of solar and stellar rotation are discussed, and an estimate is made for the frequency of occurrence of planetary systems in the universe.

Huang, S.-S.↗
NASA NTRS1973

Problems of gaseous motion around stars

A distinction is drawn between radial and tangential modes of ejection from stars, and the possible flow patterns are described. They are: expanding streams, falling streams, jet streams, circulatory streams, and gaseous envelopes. Motion around Be stars is discussed at some length, as a preliminary to studying more complicated flow in binary systems. The rotational velocity of the Be star is insufficient to form the ring. It appears likely that radial instability is temperature sensitive. Rings and disks in binary systems are discussed from the point of view of periodic orbits for particles within the gravitational field of such a system. The formation of these rings is discussed. The expected relation between rotational velocity of the ring and the orbital period is discussed. The relation of circumstellar streams to period changes is mentioned. Finally, the influence of magnetic fields on the circumstellar material and the system is discussed.

Huang, S.-S.↗
NASA NTRS1972

Disk and ring structure in the universe.

For a gas or dust cloud with a net angular momentum about a central mass, the stable shape is a rotating ring or disk, for a very simple reason. Collisions among the cloud's particles dissipate the energy of the random motions, while the rotational energy is maintained by the conservation of angular momentum. The angular momentum can be very easily imparted to matter. A ring or disk structure is, therefore, found in many celestial objects from asteroids to galaxies. The most impressive and obvious disk structures in the universe are the spiral galaxies. It is thought that the planetary system was formed from a flat disk of dust and gas. Much observational evidence shows that the thin, flat, concentric rings around the planet Saturn are composed of a host of individual particles.

Huang, S.-S.↗