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  • Humans  (741)
  • Astrophysics  (287)
  • 2000-2004  (1,028)
  • 2002  (1,028)
  • 1
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    NASA's Laboratory Astrophysics Workshop: Opening Remarks (2002)
    In:  CASI
    Details
    Publication Date: 2019-08-28
    Description: The Astronomy and Physics Division at NASA Headquarters has an active and vibrant program in Laboratory Astrophysics. The objective of the program is to provide the spectroscopic data required by observers to analyze data from NASA space astronomy missions. The program also supports theoretical investigations to provide those spectroscopic parameters that cannot be obtained in the laboratory; simulate space environment to understand formation of certain molecules, dust grains and ices; and production of critically compiled databases of spectroscopic parameters. NASA annually solicits proposals, and utilizes the peer review process to select meritorious investigations for funding. As the mission of NASA evolves, new missions are launched, and old ones are terminated, the Laboratory Astrophysics program needs to evolve accordingly. Consequently, it is advantageous for NASA and the astronomical community to periodically conduct a dialog to assess the status of the program. This Workshop provides a forum for producers and users of laboratory data to get together and understand each others needs and limitations. A multi-wavelength approach enables a cross fertilization of ideas across wavelength bands.
    Keywords: Astrophysics
    Type: Proceedings of the NASA Laboratory Astrophysics Workshop; 15-16; NASA/CP-2002-211863
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  • 2
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    The Very Slow Wind from the Pulsating Semiregular Red Giant, L2 Puppis (2002)
    In:  Other Sources
    Details
    Publication Date: 2019-08-17
    Description: We have obtained 1 1.7 and 17.9 micron images at the Keck I telescope of the circumstellar dust emission from L(sub 2) Pup, which is one of the nearest ( D = 61 pc) mass-losing, pulsating red giants that has a substantial infra-red excess. We propose that the star is losing mass at a rate of approx.3 x 10(exp -7) Solar Mass/yr. Given its relatively low luminosity (approx. 1500 Solar Luminosity), relatively high effective temperature (near 3400 K), relatively short period (approx. 140 days), and inferred gas outflow speed of 3.5 km/s, standard models for dust-driven mass loss do not apply. Instead, the wind may be driven by the stellar pulsations, with radiation pressure on dust being relatively unimportant. as described in some recent calculations. L(sub 2) Pup may serve as the prototype of this phase of stellar evolution, in which a star could lose approx. 15% of its initial main-sequence mass. Subject headings: circumstellar matter - stars: individual (L2 Puppis) - stars: mass loss
    Keywords: Astrophysics
    Type: The Astrophysical Journal (ISSN 0004-637X); 569; 2, Pt. 1; 964-974
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  • 3
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    Experimental Simulations of Large-Scale Collisions (2002)
    In:  CASI
    Details
    Publication Date: 2019-08-17
    Description: This report summarizes research on the effects of target porosity on the mechanics of impact cratering. Impact experiments conducted on a centrifuge provide direct simulations of large-scale cratering on porous asteroids. The experiments show that large craters in porous materials form mostly by compaction, with essentially no deposition of material into the ejecta blanket that is a signature of cratering in less-porous materials. The ratio of ejecta mass to crater mass is shown to decrease with increasing crater size or target porosity. These results are consistent with the observation that large closely-packed craters on asteroid Mathilde appear to have formed without degradation to earlier craters.
    Keywords: Astrophysics
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  • 4
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    Long-Term Dynamics of Small Bodies in the Solar System (2002)
    In:  CASI
    Details
    Publication Date: 2019-08-17
    Description: As part of the NASA Planetary Geology and Geophysics program, Prof. Norm Murray (CITA (Canadian Institute of Theoretical Astrophysics)) and I have been conducting investigations of the long-term dynamics of small bodies in the outer solar system. This grant, and its successor NAG5-10365, supports travel for collaboration by the Investigators and also supports Murray during an annual one month visit to the CfA (Harvard-Smithsonian Center for Astrophysics) for further collaboration. In the course of this grant we made a number of advances in solar system dynamics. For example, we developed an analytic model for the origin and consequence of chaos associated with three-body resonances in the asteroid belt. This has been shown to be important for the delivery of near Earth objects (NEO). We later extended this model to three-body resonances among planets. We were able to show that the numerically identified chaos among the outer planets results from a three-body resonance involving Jupiter, Saturn, and Uranus. The resulting paper was awarded the 1999 Newcomb Cleveland award from the AAAS (American Association for the Advancement of Science). This award singles out one paper published in Science each year for distinction. A list of grant-related publications is presented, with abstracts included.
    Keywords: Astrophysics
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  • 5
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    Infrared Spectroscopy of Star Formation in Galactic and Extragalactic Regions (2002)
    In:  CASI
    Details
    Publication Date: 2019-08-17
    Description: This report details work done in a project involving spectroscopic studies, including data analysis and modeling, of star-formation regions using an ensemble of archival space-based data including some from the Infrared Space Observatory's Long Wavelength Spectrometer and Short Wavelength Spectrometer, and other spectroscopic databases. We will include four kinds of regions: (1) disks around more evolved objects; (2) young, low or high mass pre-main sequence stars in star-formation regions; (3) star formation in external, bright IR (infrared) galaxies; and (4) the galactic center. During this period, work proceeded fully on track and on time. Details on workshops and conferences attended and research results are presented. A preprint article entitled 'The Far Infrared Lines of OH as Molecular Cloud Diagnostics' is included as an appendix.
    Keywords: Astrophysics
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  • 6
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    Magnetohydrodynamic Modeling of Coronal Evolution and Disruption (2002)
    In:  CASI
    Details
    Publication Date: 2019-08-17
    Description: Flux cancellation, defined observationally as the mutual disappearance of magnetic fields of opposite polarity at the neutral line separating them, has been found to occur frequently at the site of filaments (called prominences when observed on the limb of the Sun). During the second year of this project, we have studied theoretically the role that flux cancellation may play in prominence formation, prominence eruption, and the initiation of coronal mass ejections. This work has been in published in two papers: "Magnetic Field Topology in Prominences" by Lionello, Mikic, Linker, and Amari and "Flux Cancellation and Coronal Mass Ejections" by Linker, Mikic, Riley, Lionello, Amari, and Odstrcil.
    Keywords: Astrophysics
    Type: SAIC-03/8011:APPAT-320 , Rept-01-0157-04-1047-100
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  • 7
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    Interchannel Coupling in the Photoionization of Atoms and Ions in the X-Ray Range (2002)
    In:  CASI
    Details
    Publication Date: 2019-08-17
    Description: To understand how this interchannel coupling, so important in neutral atoms, applies to positive ions, a research program has been initiated to deal with this question, i.e., a program to quantify the effects of interchannel coupling in ionic photoionization, thereby assessing existing photoionization data bases in the x-ray region. To accomplish this task, we have employed the Relativistic Random-Phase-Approximation (RRPA) methodology which includes significant aspects of electron-electron correlation, including interchannel coupling. The RRPA methodology has been found to produce excellent agreement with experiment for neutral Ne at photon energies in the 1 keV range.
    Keywords: Astrophysics
    Type: Proceedings of the NASA Laboratory Astrophysics Workshop; 70-72; NASA/CP-2002-211863
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  • 8
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    Laboratory Studies of the X-ray Emission Produced by the Interaction of Solar Wind Heavy Ions with Comets (2002)
    In:  CASI
    Details
    Publication Date: 2019-08-17
    Description: The process of X-ray emission following charge exchange between solar wind heavy ions and cometary gases is studied in the laboratory. The emission is recorded with the spare ASTRO-E 6x6 microcalorimeter array. The microcalorimeter affords a resolution of better than 10 eV in the range of X-ray energies of interest arid thus individual emission lines can be resolved. Our present measurements focus on the most abundant K-shell heavy ions found in the solar wind. In particular, we measure the K-shell emission of bare C, N, O, and Ne, and their hydrogenlike counter parts interacting with such gases as CO2, N2, and CH4. Several results are noted that had not been considered in the early cometary X-ray models.
    Keywords: Astrophysics
    Type: Proceedings of the NASA Laboratory Astrophysics Workshop; 235-237; NASA/CP-2002-211863
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  • 9
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    Measurement of Metastable Lifetimes of Highly-Charged Ions (2002)
    In:  CASI
    Details
    Publication Date: 2019-08-17
    Description: The present work is part of a series of measurements of metastable lifetimes of highly-charged ions (HCIs) which contribute to optical absorption, emission and energy balance in the Interstellar Medium (ISM), stellar atmospheres, etc. Measurements were carried out using the 14-GHz electron cyclotron resonance ion source (ECRIS) at the JPL HCI facility. The ECR provides useful currents of charge states such as C(sup(1-6)+), Mg(sup(1-6)+) and Fe(sup(1-17)+). In this work the HCI beam is focused into a Kingdon electrostatic ion trap for measuring lifetimes via optical decays.
    Keywords: Astrophysics
    Type: Proceedings of the NASA Laboratory Astrophysics Workshop; 93-95; NASA/CP-2002-211863
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  • 10
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    Research and Project Activities in Astrophysics (2002)
    In:  CASI
    Details
    Publication Date: 2019-08-16
    Description: In collaboration with G Micela, S. Sciortino, and others at the Osservatorio Astronomico di Palermo G. S. Valens, we conducted studies of X-ray emission from normal stars, primarily via observations of several open star clusters and star forming regions (viz. the Pleiades, NBC 2516, NBC 2264, and the Orion Nebula Cluster). Our work was based on combined data from several X-ray observatories, Einstein, ROSAT, XMM-Newton and Chandra, as well as ground-based optical and radio data. Preliminary results were presented at several meetings: HEAD/AAS, November, 1997 a 195th AAS Meeting, January 2000 a Three Islands Conference, April 2000 a X-ray Astronomy 2000, September 2000 a 197th AAS Meeting, January 2001 Two Years of Science with Chandra, September 2001
    Keywords: Astrophysics
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