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  • 1
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    Gaspra's shape and surface features: Comparison to small satellites (1992)
    In:  CASI
    Details
    Publication Date: 2013-08-29
    Description: The several thousand asteroids constitute the second largest population of substantial solid objects in the solar system (there are probably more comets), and have been studied from the Earth for nearly two centuries. Asteroids are important members of the solar system for several reasons, among them: (1) they contain the materials that reflect the processes going on early in the time of planet formation; (2) their impacts have been the major external influences on the surface of some terrestrial planets; and (3) their impacts on Earth have probably had major effects on biologic evolution. This paper examines and describes the asteroid Gaspra, and compares it to small satellites.
    Keywords: ASTROPHYSICS
    Type: Lunar and Planetary Inst., Twenty-Third Lunar and Planetary Science Conference; p 49-52
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  • 2
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    Shock drift acceleration (1985)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: This is a review of the fundamental physics of the interactions of charged particles treated individually while they interact with fast mode magnetohydrodynamic shocks. Numerical simulation and analytical theory are used to develop predictions of the expected characteristics of this process strong upstream anisotropies directed along the magnetic field and downstream anisotropies tending to be peaked more perpendicular to the field; relatively more of the enhancement of higher-energy particles occurring upstream; sensitive dependence on shock normal to magnetic field angle of the efficiency of energization. Observations which display all of the above characteristics are reviewed. Also discussed is the relationship of shock drift acceleration to the models for stochastic transport of charged particles in the vicinity of shocks. Extensions of this work in both the observational and theoretical approaches are discussed.
    Keywords: ASTROPHYSICS
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  • 3
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    Near-infrared observations of young stellar objects in the Rho Ophiuchi dark cloud (1992)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: We have conducted an imaging survey of 1.4 sq pc of the Rho Ophiuchi dark cloud in the J, H, and K near-infrared photometric bands. Approximately 337 of our 481 detected sources are associated with the cloud, and we estimate that 48 percent of these have near-infrared excesses, indicative of disks or circumstellar material surrounding these young stellar objects (YSOs). The K-band luminosity function is significantly different in different regions of our survey area, suggesting that YSOs in these regions have different ages or mass functions. We estimate that the entire survey area has a high star-formation efficiency, at roughly 23 percent. Finally, our many newly detected sources provide a relatively large, uniformly sensitive sample of objects for study at longer wavelengths to better determine true source luminosities and evolutionary lifetimes.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 395; 2 Au; 516-528
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  • 4
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    The Rho Ophiuchi cloud young stellar population - Results of a near-infrared study (1991)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: An imaging survey of 1.4 sq pc of the Rho Ophiuchi dark cloud in the J, H, and K near-infrared photometric bands was conducted. Approximately 332 of the 481 detected sources are associated with the cloud, and 30 percent of these have near-infrared excesses, indicative of disks or circumstellar material surrounding these young stellar objects (YSOs). The K-band luminosity function is significantly different in different regions of the survey area, suggesting that YSOs in these regions have different ages or mass functions. The entire survey area has a high star formation efficiency of about 23 percent. Finally, many newly detected sources provide a relatively large, uniformly sensitive sample of objects for study at longer wavelengths to better determine true source luminosities and evolutionary lifetimes.
    Keywords: ASTROPHYSICS
    Type: Societa Astronomica Italiana, Memorie (ISSN 0037-8720); 62; 4 19
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  • 5
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    IRAS observations of dust heating and energy balance in the Rho Ophiuchi dark cloud (1989)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: The equilibrium process dust emission in the Rho Ophiuchi dark cloud is studied. The luminosity of the cloud is found to closely match the luminosity of the clouds's known embedded and external radiation sources. There is no evidence for a large population of undetected low-luminosity sources within the cloud and unknown external heating is also only a minor source of energy. Most of the cloud's luminosity is emitted in the mid-to-far-IR. Dust temperature maps indicate that the dust is not hot enough to heat the gas to observed temperatures. A simple cloud model with a radiation field composed of flux HD 147889, S1, and Sco OB2 associations predicts the observed IRAS 60 to 100 micron in-band flux ratios for a mean cloud density n(H2) = 1400. Flattened 12 and 25 micron observations show much extended emission in these bands, suggesting stochastic heating of very small grains or large molecules.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 339; 258-267
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  • 6
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    IRAS observations of young stellar objects in the Corona Australis dark cloud (1992)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: The young stellar object (YSO) population associated with the dark cloud complex in Corona Australis is studied by synthesizing IRAS data with newly obtained near-IR and mid-IR photometry and previously published optical/IR data. Twenty-four YSOs in the Cr A complex are identified. The observed range of spectral energy distribution shapes and bolometric luminosities are consistent with those observed in other dark clouds. The duration and efficiency of star formation are found to be similar to the Rho Ophiuchi IR cluster. The low number of YSOs compared to other dark clouds is understood by a reevaluation of the molecular mass of the R Cr A cloud which shows it to be much less massive than previously assumed.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 397; 2; p. 520-533.
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  • 7
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    Infrared images of the young cluster NGC 2264 (1993)
    In:  Other Sources
    Details
    Publication Date: 2019-08-27
    Description: Initial results of an extensive IR imaging survey of the young cluster NGC 2264 and a nearby galactic control field are presented. A large portion of the cluster was imaged in each of the three standard near-IR colors (J, H, and K) with an IR array camera. On the basis of a comparison of these observations, the size of the cluster population is estimated, and the nature of its members is investigated. The cluster is found to contain 360 +/- 130 members. The slope of the K luminosity function of the cluster is significantly steeper than that expected for a cluster of ZAMS stars, and appears to flatten out or turn over at an apparent K magnitude of roughly 13.0-14.0. An analysis of the JHK color-color diagrams of the cluster and control fields shows that approximately 170 sources observed toward the cluster have colors indicative of intrinsic excess IR emission.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 408; 2; p. 471-483.
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