Engineering topics

Barnes, T. G., III

Publications and source records attributed to Barnes, T. G., III.

10 records

NASA NTRS1981

The visual surface brightness relation and the absolute magnitudes of RR Lyrae stars. II - RR Lyrae and X Arietis

The theoretical surface brightness relation for RR Lyrae stars has been combined with new VR photometry to determine distances, radii, and absolute magnitudes for X Arietis and RR Lyrae. For X Arietis, a pulsational variation in the radius from 5.06 solar radii to 5.96 solar radii, a distance of 495 + or - 50 pc, and an intensity mean absolute magnitude of +0.59 + or - 0.25 is obtained. The corresponding quantities for RR Lyrae are 4.81-5.67 solar radii, 263 + or - 39 pc, and an intensity mean absolute magnitude of +0.61 + or - 0.35. The larger errors quoted for RR Lyrae are due to uncertainties arising from the Blazhko effect. Results are discussed in the context of the dependence of RR Lyrae absolute magnitudes on metal abundance.

Manduca, A.↗

NASA NTRS1981

On the mass of the Cepheid X Cygni

Using a new non-Lagrangian hydrodynamic radiation transport code, models of the Cepheid X Cygni have been calculated and compared with new observations. Adopting an effective temperature of 5300 K, the luminosity was varied for stellar masses of 6, 8, and 9 solar masses in order to obtain a period of 16.4d. The results indicate that in order to find reasonable agreement between the light curves as calculated and observed, the mass used in the models must be nearly the evolutionary mass, not some 60% less as found in earlier work for Cepheids with periods from 7d to 10d. In addition, the new observations support the physical reality of the so-called 'artificial viscosity dip'.

Davis, C. G.↗

NASA NTRS1980

Observational studies of Cepheids. I - BVRI photometry of bright Cepheids

Over 1,000 differentially determined photoelectric BVRI observations and the resulting light curves are presented for 24 bright Cepheids accessible from Northern Hemisphere observatories. The internal precision of these data is shown to be better than + or - 0.01 mag, and the accuracy of transformation to the Johnson BVRI system is nearly as good.

Moffett, T. J.↗

NASA NTRS1980

An independent Cepheid distance scale: Current status

An independent distance scale for Cepheid variables is discussed. The apparent magnitude and the visual surface brightness, inferred from an appropriate color index, are used to determine the angular diameter variation of the Cepheid. When combined with the linear displacement curve obtained from the integrated radial velocity curve, the distance and linear radius are determined. The attractiveness of the method is its complete independence of all other stellar distance scales, even though a number of practical difficulties currently exist in implementing the technique.

Barnes, T. G., III↗

NASA NTRS1980

Photoelectric observations of lunar occultations

Photoelectric observations of 13 lunar occultation disappearances during a March 1979 Hyades passage are reported. Three double stars (SAO 93925 = Fin 342 = 70 Tau, SAO 93961 = ADS 3248, and SAO 95419 = Kui 24) and one possible double (SAO 93950 = 75 Tau) were detected. A brief description is given of the Purdue University pulse-counting photometer as modified for occultation observations.

Fekel, F. C.↗

NASA NTRS1979

A UBVRI equatorial extinction star network

An equatorial-extinction star network, based on 1503 observations of 37 stars, is presented. These results together with those of Crawford et al. (1971) provide a well-determined UBVRI extinction network. Identification charts are included.

Barnes, T. G., III↗

NASA NTRS1979

Equatorial UBVRI photoelectric sequences

From 1335 BVRI observations of 189 stars in selected areas 92-115, Landolt's (1973) network of faint UBV standards has been extended to R I. Of these stars, 173 have four or more observations. The (U-B) values of Landolt are adopted, and a well-observed equatorial faint-star network is presented on the Johnson UBVRI photometric system.

Moffett, T. J.↗

NASA NTRS1979

Secondary standards for BVRI photometry

A thorough test of Fernie's instrumentation system for matching the Johnson BVRI photometric system has been made. From 1,526 observations of 186 stars in the Arizona-Tonantzintla Catalogue, there were found excellent transformations, except for a slight curvature in the (B-V) transformation, which is easily removed, and a difficulty in (R-I) for highly reddened stars. Photometric values and their uncertainties are given for all the stars, and these are of sufficient quality to serve as secondary standards in BVRI for small- to moderate-size telescopes (1-m).

Moffett, T. J.↗

NASA NTRS1976

Comments on the optical counterpart of the X-ray source 3U 0352 + 30

Spectral and photometric observations of ADS 2859 B, the faint companion to X Per, show it to be a normal M giant rather than a T Tauri star as previously reported in the literature. Consequently, there is no substantive reason to associate it with the X-ray source 3U 0352 + 30. A search for rapid light variations of X Per itself proved negative.

Moffett, T. J.↗

NASA NTRS1974

Atmospheric motions in red supergiants

Radial velocities obtained from interferometric spectra of a alpha Ori, alpha Her, and alpha Sco have been analyzed to investigate expansion and other large-scale motions in their atmospheres. In alpha Ori evidence of such motions is found. They appear to be sporadic in time or position on the surface of the star. If these motions are an observational indication of mass loss, they lead to extremely high instantaneous loss rates. It has not been possible to infer an average rate of mass loss.

Brooke, A. L.↗