Showing papers in "The Astronomical Journal in 1973"
789 citations
TL;DR: In this article, a two-dimensional spectral classification system for the O stars is presented, and the separation of the Carina-Sagittarius arm from the local arm along the entire longitude range of 255 to 20 deg
Abstract: New results pertaining to the two-dimensional spectral classification system for the O stars are presented. Classifications for additional stars in both hemispheres are given, and two groups of peculiar Of-like spectra are described and illustrated. Some refinements of the absolute-magnitude calibration are discussed. The space distribution projected into the galactic plane is derived for all nonpeculiar O stars with classifications. The most striking result is the clear separation of the Carina-Sagittarius arm from the local arm along the entire longitude range of 255 to 20 deg . The good agreement with previous results for other types of young objects provides evidence in support of the new luminosity classification for the O stars. (auth)
329 citations
208 citations
152 citations
TL;DR: In this paper, photoelectric observations of the entire lunar disk made in 1964-1965 over phase angles from 6 to 12 deg in nine narrow bands from 0.35 to 1.0 microns and in UBV are reviewed.
Abstract: Photoelectric observations of the entire lunar disk made in 1964-1965 over phase angles from 6 to 12 deg in nine narrow bands from 0.35 to 1.0 microns and in UBV are reviewed. Phase curves are presented as a function of wavelength. The results confirm a reddening with increasing phase angle found by previous investigators for particular areas.
140 citations
TL;DR: In this paper, the centinuum spectra of diacrete radio sources measured with the 10-22-MHz T- arrays at the Dominion Radio Astrophysical Observatory were combined with observations from higher frequencies to construct and classify the centimetric spectras of 225 sources in the range 10-2000 MHz.
Abstract: Flux densities of diacrete radio sources measured with the 10-22-MHz T- arrays at the Dominion Radio Astrophysical Observatory are combined with observations from higher frequencies to construct and classify the centinuum spectra of 225 sources in the range 10-2000 MHz. New or revised flux densities are given for 38 sources at 10 and 22 MHz, together wiih revised calibration fuctors for previously published flux densities at these frequencies. Scales used for other published flux densities in the range 12-178 MHz are assessed and an intenally consistent set of scale revision factors is derived. The spectral propenties of complete samples of extragalactic sources selected at 10, 178, and 1400 MHz are compared, using spectral indices evaluated at six frequencies. Classes of sources having unusually high- and low-spectral indices are identified. Quasistellar sources are found to have spectral indices distributed differently from those of radio galaxies; quasistellar sources with power-law regions of their spectra have generally higher spectral indices there than those of the galaxies. A small group of sources identified with blank fields contains some members whose spectral indices are uncharacteristic of distant radio galaxies or of quasistellar sources. There appears to be no evolutionary effect present in the spectral index-luminositymore » correlation for radio galaxies. (auth)« less
93 citations
TL;DR: In this article, a realistic model was proposed to show how satellites' gravitational interaction can halt their differential tidal evolution when resonant commensurabilities of their orbital periods are reached.
Abstract: Analysis of a realistic model shows how satellites' gravitational interaction can halt their differential tidal evolution when resonant commensurabilities of their orbital periods are reached. The success of this study lends support to the hypothesis that orbit-orbit resonances among satellites in the solar system, including the Titan-Hyperion case, did evolve as a result of tidal energy dissipation. Consideration of the time scale for this evolution process, possible now that the capture mechanism has been revealed, can offer more sophisticated constraints on the tidal dissipation function, Q, and on past orbital conditions.
76 citations
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TL;DR: In this paper, the authors measured spectral reflectivities (0.3-1.1 micron) for 32 asteroids and found that the most common spectral curve types are: (a) reddish curves with 10% absorptions near 0.95 micron or beyond 1.0 micron, due to Fe(2+) in minerals such as pyroxenes; (b) flat curves in the visible and near-IR with sharp decreases in the UV and (c) flat curve even into the UV.
Abstract: We measured spectral reflectivities (0.3-1.1 micron) for 32 asteroids. There are at least 14 different curve types. Common types are: (a) reddish curves with 10% absorptions near 0.95 micron or beyond 1.0 micron, due to Fe(2+) in minerals such as pyroxenes; (b) flat curves in the visible and near-IR with sharp decreases in the UV and (c) flat curves even into the UV. Several asteroids show probable color variations with rotation, especially 6 Hebe. A sample of 102 asteroids with reliably known colors is derived from the reflectivities and from earlier colorimetry. Several correlations of colors and spectral curve types with orbital and physical parameters are examined: (1) asteroids with large aphelia have flat reflectivities while those with small perihelia are mostly reddish, (2) curve types show evidence for clustering on an a vs e plot, with 0.95 micron bands occuring mainly for Mars-approaching asteroids, (3) no strong correlation exists between color and either proper eccentricity or proper inclination.
66 citations
TL;DR: In this paper, the processes used for the identification, filtering, and compression of McDonald Observatory lunar-laser ranging data are presented in sufficient detail to justify the confidence levels currently assigned to these data.
Abstract: The processes used for the identification, filtering, and compression of McDonald Observatory lunar-laser ranging data are presented in sufficient detail to justify the confidence levels currently assigned to these data. The observational normal points are tabulated for the interval 1969-1971.
TL;DR: In this paper, the rotational polarization curves indicate that the lightcurves are mostly due to shape, but some albedo variation over the surface is detected as well, showing some reddening with phase.
Abstract: UBV photometry, lightcurves, a polarization-phase relation, and rotational polarization curves of Toro were obtained, June-August 1972. The average colors are B-V = 0.87 and U-B = 0.47 mag, showing some reddening with phase. The geometric albedo of Toro in the B filter is 0.14 which corresponds to an effective mean radius of 2.2 km plus or minus 0.4 (p.e.). The rotational polarization curves indicate that the lightcurves are mostly due to shape, but some albedo variation over the surface is detected as well. The shape is elongated, and probably irregular, with a cross-sectional area ratio of about 3.2, the maximum effective radius is 2.8 km and the minimum, 1.6 km.
TL;DR: In this paper, high-resolution spectrophotometric observations from 0.6 to 2.0 microns were used to study the Jovian and Saturnian limb darkening at 0 deg phase angle.
Abstract: High spatial resolution spectrophotometric observations (from 0.6 to 2.0 microns) are used to study the Jovian and Saturnian limb darkening at 0 deg phase angle. The limb-darkening coefficients (k) of the Minnaert function are 1.0 over Jupiter's entire disk and between 0.75 and 0.90 for different latitudes on Saturn. These data are used to derive geometric albedoes (G) for the various belts, zones, spots, and regions observed on Jupiter and Saturn. These values of G and k are in turn used to show that an isotropic scattering model is invalid for Jupiter and that at least an asymmetric scattering function, such as the Euler function, is needed to fit the Jovian data. The Jovian scattering function is found to generally vary between 0.960 (1 + 0.85 cos theta) and 0.994 (1 + 0.42 cos theta) as a function of wavelength and the feature observed. The Saturn geometric albedoes and values of k indicate that Euler's function fails to adequately model the scattering properties of Saturnian clouds; they may be better represented by a cumulus cloud model.
TL;DR: In this article, the photometric function of the Saturn ring system at visual (V) wavelengths is interpreted in terms of a simple scattering model, based on a plane-parallel slab of isotropically scattering particles.
Abstract: Reliable data defining the photometric function of the Saturn ring system at visual (V) wavelengths are interpreted in terms of a simple scattering model. To facilitate the analysis, new photographic photometry of the ring has been carried out utilizing the Lowell observatory plate collection. Homogeneous measurements of the mean surface brightness (rings A and B together), covering almost the complete range in planetocentric solar declination angle, are presented. The ring model adopted is a plane-parallel slab of isotropically scattering particles; the single scattering albedo and the perpendicular optical thickness are both arbitrary. Results indicate that primary scattering is inadequate to describe the photometric properties of the ring; multiple scattering predominates for all angles of tilt with respect to the Sun and Earth.
TL;DR: A Maximum Entropy Method spectral analysis of van de Kamp's data on the perturbation motions of Barnard's Star suggests that several planets may be in orbit about it as mentioned in this paper.
Abstract: A Maximum Entropy Method spectral analysis of van de Kamp's data on the perturbation motions of Barnard's Star suggests that several planets may be in orbit about it. The preferred interpretation requires planets with 26-, 11-, 3.8- , 2.9-, and 2.4-year orbital periods having masses rarging from 0.7 to 1.6 times the mass of Jupiter. The interpretation is based upon probability and likelihood arguments. (auth)