Engineering Papers⌕ Search

Engineering topics

Eaton, J. A.

Publications and source records attributed to Eaton, J. A..

28 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1980

Ultraviolet colors of W Ursae Majoris - Gravity darkening, temperature differences, and the cause of W-type light curves

The paper presents photometry of the prototype W UMa binary system in three ultraviolet bands with the ANS satellite. It was found that W UMa has low-gravity darkening beta of 0.03; that temperature differences between the components not established by gravity darkening are insignificant; and that the bolometric albedo is not very large. It was also found that W UMa is limb-darkened in the ultraviolet region, and that the inner hemisphere of the less massive component is hotter than that predicted by gravity darkening and the reflection effect. It was concluded that about 20% of the surface area of the component responsible for large gravity darkening is covered by dark spots distributed uniformly in the longitudinal direction. An observational value of the convective darkening exponent of 0.054 plus or minus 0.02 is proposed.

Eaton, J. A.↗
NASA NTRS1979

Starspots as the cause of the intrinsic light variations in RS Canum Venaticorum type stars

A starspot model is proposed to interpret the light curves of three RS CVn type binary systems. Two of the systems are RS CVn and SZ Psc, which are detached, while the third system, RT Lac, is semidetached. Solar activity and the surface activity of the RS CVn type stars are compared. It is found that the spot model permits the detailed fitting of both the out-of-eclipse complications and the distorted shapes of the secondary eclipses in the light curves of these stars.

Eaton, J. A.↗
NASA NTRS1978

Tidal effects in the O-type eclipsing system LY Aurigae

Existing photometry of the O9.5 III eclipsing binary LY Aur is discussed and combined into a visual mean light curve. It is found that the observed light curve is incompatible with previous solutions based on the Russell model, but a respectable fit to the observed light curve can be achieved by assuming von Zeipel gravity darkening provided the system is allowed to be in marginal contact, which involves an unrealistically large change in the mass ratio to obtain the appropriate eclipse depths and light ratio. The alternative possibilities are considered that the primary is tidally distorted more than expected for its relative radius and the observed mass ratio or that von Zeipel gravity darkening is not appropriate for O-type stars and photometric effects exist which magnify the effects of the primary's physical distortions in the light curve. A solution is favored in which the ratio of radii is near 0.75 and the primary is very highly gravity darkened relative to von Zeipel's law.

Eaton, J. A.↗
NASA NTRS1978

A synthetic light curve solution of the OAO-2 ultraviolet light curves of u Herculis

OAO 2 ultraviolet photometry of the eclipsing binary u Her is reported and interpreted. The light curve of u Her is found to be intrinsically variable, the variable light curve is rectified, and the adjusted light and color curves are plotted. A simultaneous solution to three adjusted OAO 2 light curves (at respective wavelengths of 3320, 1910, and 1550 A) is obtained by using the Roche model. The results indicate that the system is semidetached if the gravity darkening of the secondary is not significantly larger than expected. It is suggested that the primary is responsible for the variable light curve, that the monochromatic albedo of the secondary is very low at short wavelengths, and that the depth of primary eclipse is strongly dependent on the primary's limb darkening.

Eaton, J. A.↗
NASA NTRS1977

Random variations in the ultraviolet spectrum of Beta Lyrae

Spectrophotometric scans of Beta Lyrae over the wavelength range from 1100 to 3700 A are analyzed which were obtained at different times with different resolutions by the OAO 2 satellite and from the ground. A model atmosphere with normal H and He abundances, an electron temperature of 11,000 K, and log g of 3.0 is found to fit the visual region of the spectrum well but to be a poor representation in the Balmer continuum. It is shown that a large complex emission feature dominates the spectrum from about 1700 to 2200 A, that there is a very pronounced strengthening of the spectrum just shortward of the 1550-A C IV feature at phase 0.69, and that the overall level of the spectrum shortward of 1400 A is quite high in comparison with the broad emission feature. A model is discussed in which the light from a disk-shaped secondary is highly concentrated toward the polar regions.

Bless, R. C.↗
NASA NTRS1976

Ultraviolet photometry from the Orbiting Astronomical Observatory. XXII Ultraviolet light variation of Beta Lyrae

Six-color ultraviolet light curves of the complex eclipsing binary system Beta Lyr were obtained with the OAO-2 Wisconsin Experiment Package. The filters had a typical width at half maximum of 150 to 200 A and were centered at 1430, 1550, 1910, 2460, 2980, and 3320 A. The most striking characteristics of the ultraviolet light curves are that the secondary minimum deepens at shorter wavelengths. This indicates that we are not observing the eclipse effect of two stars having roughly a Planckian distribution of energy. In combination with the high-resolution far-ultraviolet spectra of Beta Lyr recently obtained with Copernicus (OAO-3) Princeton Telescope Spectrometer, it is concluded that the far-ultraviolet light curves are dominated by emission from the high-temperature gas surrounding the binary system. The ultraviolet observations of OAO-2 and Copernicus are consistent with a model in which the enigmatic secondary component involves a gravitationally collapsed object; i.e., a black hole. However, alternative models are also admissible.

Kondo, Y.↗
NASA NTRS1975

Ultraviolet photometry and spectrophotometry of Algol

OAO-2 blue and UV light curves and spectrophotometric observations are used to establish effective temperatures and luminosities for the three components of the eclipsing Algol (beta Persei) system. An essentially complete energy distribution is given for Algol, and the fundamental properties - geometrical quantities, wavelength-dependent quantities and derived astrophysical quantities - are presented for the star.

Eaton, J. A.↗