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  • 1
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    Determining asteroid masses from perturbations on Mars (1984)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: The orbit of Mars is perturbed more than 5 m, a value compatible with the accuracy of the Viking Lander ranging data, by about three dozen asteroids. In addition to larger asteroids throughout the belt, significant perturbations of long period are generated by smaller objects near commensurabilities with Mars. The largest periodic terms induced by 1 Ceres and 2 Pallas have amplitudes of 0.8 and 0.2 km, respectively, both with 10-year periods. Due to a near commensurability, 4 Vesta causes a 5-km, 52-year term. While the Viking ranges will yield significant mass determinations for the largest three asteroids, and some of the smaller bodies should be detectable, it will be difficult to separate the smaller bodies with useful accuracies. Accurate discrimination must await range data from future missions to Mars or other bodies in the neighborhood of the asteroid belt. The Viking ranges can also yield improved masses for the outer planets (except Pluto), an application which is being exploited by groups analyzing these data. Uncertainties in the asteroid masses limit the ultimate accuracy of the Viking determinations of both the long time scale motion of the system of the inner four planets with respect to an inertial frame and the rate of change of the gravitational constant.
    Keywords: ASTRONOMY
    Type: Icarus (ISSN 0019-1035); 57; 1-13
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  • 2
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    Photometry with Multi-anode Microchannel Arrays (mamas) and Charge Injection Devices (cids) (1984)
    In:  CASI
    Details
    Publication Date: 2014-09-18
    Description: The characteristics of two kinds of detectors are summarized with emphasis on those aspects that would affect their use in high accuracy astronomical photometry. The first type, the multianode microchannel arrays (MAMA), are a family of pulse counting array detectors. Components and operation principles are reviewed and quantum efficiency, noise characteristics, and dynamic range characteristics are described. The second type, charge injection devices (CID), are discussed in reference to their applicability to photometric detection at optical wavelengths.
    Keywords: ASTRONOMY
    Type: NASA. Ames Research Center Proc. of the Workshop on Improvements to Photometry; p 203-215
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  • 3
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    JHK photometry of Comet Bowell (1982I) (1984)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: Comet Bowell (1982I) was observed at JHK (1.25, 1.68, 2.25 microns) with the NASA Infrared Telescope Facility on March 10, 1981, June 3-5, 1981, and February 22, 1982. The inner coma was no brighter near perihelion in February 1982 than it was in 1981. Total area x albedo of the grains within 10,000 km of the nucleus was about 5 x 10 to the 12th/sq cm.
    Keywords: ASTRONOMY
    Type: Icarus (ISSN 0019-1035); 60; 445-448
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  • 4
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    The 157 Micron (C II) Luminosity of the Galaxy (1984)
    In:  CASI
    Details
    Publication Date: 2014-09-17
    Description: The diffuse far infrared (C II) emission of several regions of the Galactic plane were sampled. Mechanisms for the excitation of carbon ions are discussed in reference to the role of carbon ion transitions in cooling diffuse atomic hydrogen. Observations indicate that the C II emission probably arises at the edges of giant molecular clouds and appears to have localized knot-like features. The total C II luminosity of the Galaxy is approximately 6 to 10 to the 7th power L(solar).
    Keywords: ASTRONOMY
    Type: NASA. Ames Research Center Airborne Astron. Symp.; p 260-265
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  • 5
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    IUE observations of DQ Herculis and its nebula, and the nature of the cold nova shells (1984)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The nebula ejected in the 1934 outburst of the classical nova DQ Her is remarkable for its unprecedentedly low temperature of Te 500 K as measured by Williams et al. (1978). In this paper, IUE observations are combined with Steward optical spectra. It is confirmed that the gas is quite cold. It is further shown that the gas is ionized by the radiation field of the central object. X-ray, ultraviolet, optical and infrared observations of the underlying binary are combined with the extreme-ultraviolet continuum deduced from the level of ionization of the nebula to obtain a composite energy distribution for the central object. This energy distribution bears no resemblance to that predicted by theoretical models of accretion disks. Photoionization models of the nebula using the deduced continuum, as well as theoretical accretion disk continua, are presented to show that the low electron temperature is the result of the very high metal abundances which characterize nova shells. Infrared fine-structure lines are efficient coolants, and low temperatures are achieved for a wide variety of radiation fields. The implications of these results for nebulae surrounding other old novae are discussed.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 281; 194-204
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  • 6
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    E2003 + 225 - A 3h 42m AM Herculis type binary system (1984)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The bright soft X-ray source E2003 + 225, originally discovered by the HEAO 1 low-energy detectors, has been found to be a new AM Herculis type binary. The optical counterpart shows a rich emission spectrum of He II, He I, and H as well as circular and linear polarization. Larger polarization in the near-infrared than in the ultraviolet argues for its origin as high harmonic cyclotron emission. Optical photometry, polarimetry, spectroscopy, and the X-ray light curves are all consistent with an orbital period of 222.51 m, the longest period known for AM Herculis systems, and only the second on the long side of the 2-3 hour cataclysmic variable period gap.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 277; 682-691
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  • 7
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    Infrared photometry of the dust in comets (1984)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Infrared observations of six comets ranging in heliocentric distance from 1 to 5 AU are reported. Data consist of wide and intermediate bandpass filter photometry, 1-20 microns, for periodic comets Stephan-Oterma, Swift-Gehrels, Kearns-Kwee, Gunn, and Grigg-Skjellerup and for parabolic Comet Elias (1981 XV). All of the comets show infrared temperatures hotter than a theoretical black body, indicating small absorbing grains. No emission feature at 10 microns was observed within the accuracy of the filter photometry. The photometric system is discussed in detail, and temperature-dependent corrections to monochromatic magnitudes are presented.
    Keywords: ASTRONOMY
    Type: Astronomical Journal (ISSN 0004-6256); 89; 162-169
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