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  • 1
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    Detection of the overtone of the 3.3 micron emission feature in IRAS 21282+5050 (1994)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: The 1.6-1.8 micron spectrum of the planetary nebula, IRAS 21282+5050, a strong emitter of the unidentified interstellar bands, contains a 0.02 micron wide eimission feature centered at 1.680 micron, which is well matched by laboratory spectra of the 0-2 CH stretching mode in polycyclic aromatic hydrocarbons (PAHs). We identify the new feature as the overtone of the well-known 3.3 micron band. In view of the high excitation required for emission in this band, the identification indicates that the emission is by free molecules rather than molecular moieties in solid dust grains. Modeling of the intensity ratio of the 2-0 to 1-0 band implied that the PAHs emitting in these bands contain about 60 carbon atoms. It is inferred that the nu = 2-1 hot band of the CH stretching mode occurs at about 3.43 micron and contributes to the long-wavelength shoulder of the 3.40 micron feature. The main 3.40 micron feature probably is due to aliphatic sidegroups on PAH molecules.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters (ISSN 0004-637X); 434; 1; p. L15-L18
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  • 2
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    Pulsed high-energy gamma-rays from the radio pulsar PSR1706-44 (1992)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: Gamma radiation above 100 MeV in energy has been detected from the radio pulsar PSR1706-44. The gamma emission forms a single broad peak within the pulsar period of 102 ms, in contrast to the two narrow peaks seen in the other three known high-energy gamma-ray pulsars. The emission mechanism in all cases is probably the same, the differences arising from the geometry of the magnetic and rotation axes and the line of sight. Gamma-ray emission accounts for as much as 1 percent of the total neutron star spindown energy in these pulsars, much more than emerges at optical or radio frequencies. Thus, study of this emission is important in understanding pulsar emission and evolution.
    Keywords: ASTROPHYSICS
    Type: Nature (ISSN 0028-0836); 359; 6396; p. 615, 616.
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  • 3
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    A high-frequency survey of the southern Galactic plane for pulsars (1992)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: Results of an HF survey designed to detect young, distant, and short-period pulsars are presented. The survey detected a total of 100 pulsars, 46 of which were previously unknown. The periods of the newly discovered pulsars range between 47 ms and 2.5 ms. One of the new discoveries, PSR 1259-63, is a member of a long-period binary system. At least three of the pulsars have ages less than 30,000 yr, bringing the total number of such pulsars to 12. The majority of the new discoveries are distant objects with high dispersion measures, which are difficult to detect at low frequencies. This demonstrates that the survey has reduced the severe selection effects of pulse scattering, high Galactic background temperature, and dispersion broadening, which hamper the detection of such pulsars at low radio frequencies. The pulsar distribution in the southern Galaxy is found to extend much further from the Galactic center than that in the north, probably due to two prominent spiral arms in the southern Galaxy.
    Keywords: ASTROPHYSICS
    Type: Royal Astronomical Society, Monthly Notices (ISSN 0035-8711); 255; 401-411
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  • 4
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    Negative ions in the coma of Comet Halley (1991)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: The detection of negatively charged cometary ions in the inner coma of Comet Halley is reported. These ions are observed in three broad mass peaks at 7-19, 22-65, and 85-110 AMU, with densities reaching greater than about 1/cu cm, about 0.05/cu cm, and about 0.04/cu cm, respectively, at a distance of about 2300 km from the nucleus. The ion species thought to be present include O(-), OH(-), C(-), CH(-), CN(-) and heavier complex CHO molecular ions. As negative ions are easily destroyed by solar radiation at about 1 AU, an efficient production mechanism, so far unidentified, is required to account for the observed densities. The detection of negative ions in the coma near 1 AU implies that negative ions should also be present in similar neutral gas and dust environment farther away from the sun. If the negative-ion densities are large enough, they could play an important part in physical processes such as radiative transfer or charge exchange.
    Keywords: ASTROPHYSICS
    Type: Nature (ISSN 0028-0836); 349; 393-396
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  • 5
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    A 5.75-millisecond pulsar in the globular cluster 47 Tucanae (1990)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: A pulsar with a period of 5.75 ms and a dispersion measure of 25/cu cm pc has been found in the direction of 47 Tucanae. Despite its probable origin as a member of a binary system, timing measurements show that the pulsar is now single. The observed dispersion measure is consistent with the pulsar lying outside the Galactic electron layer and within 47 Tucanae, but it is very different from the value of 67/cu cm pc for the pulsars that were reported recently as being in this globular cluster. It is suggested that the latter pulsars probably do not in fact lie within 47 Tucanae.
    Keywords: ASTROPHYSICS
    Type: Nature (ISSN 0028-0836); 345; 598-600
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  • 6
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    Photo-thermo-dissociation. I - A general mechanism for destroying molecules (1989)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Photothermodissociation (PTD) of an isolated molecule is the name of the process when a photon is absorbed by an electronic transition, the energy is transferred to the vibrations (hot molecule) and then an atom or a fragment is ejected. A statistical physics treatment is presented that goes beyond the thermal approximation and fully takes into account the isolation of the system. A model is given that permits an explicit calculation of the ejection rates of hydrogen and carbon fragments from aromatic molecules as a function of their size and internal energy. Then, the lifetime of species against PTD in different astronomical radiation fields will result when a precise dynamical evolution of their internal energy can be established.
    Keywords: ASTROPHYSICS
    Type: Astronomy and Astrophysics (ISSN 0004-6361); 213; 1-2,
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  • 7
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    Discovery of a Young, Energetic Pulsar Near the Supernova Remnant G290.1-0.8 and the Gamma-Ray Source 2EG J1103-6106 (1996)
    In:  Other Sources
    Details
    Publication Date: 2018-06-08
    Description: We report on the discovery and follow-up timing observations of a 63-ms radio pulsar, PSR J1105-6107. We show that the pulsar is young, having a characteristic age of only 63kyr. We consider its possible association with the nearby remnant G290.1-0.8 (MSH 11-61A) but uncertainties in the distances and ages preclude a firm conclusion.
    Keywords: Astronomy
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  • 8
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    Enhancement of the Accretion of Jupiters Core by a Voluminous Low-Mass Envelope (2013)
    In:  CASI
    Details
    Publication Date: 2019-07-19
    Description: We present calculations of the early stages of the formation of Jupiter via core nucleated accretion and gas capture. The core begins as a seed body of about 350 kilometers in radius and orbits in a swarm of planetesimals whose initial radii range from 15 meters to 100 kilometers. We follow the evolution of the swarm by accounting for growth and fragmentation, viscous and gravitational stirring, and for drag-induced migration and velocity damping. Gas capture by the core substantially enhances the cross-section of the planet for accretion of small planetesimals. The dust opacity within the atmosphere surrounding the planetary core is computed self-consistently, accounting for coagulation and sedimentation of dust particles released in the envelope as passing planetesimals are ablated. The calculation is carried out at an orbital semi-major axis of 5.2 AU and an initial solids' surface density of 10/g/cm^2 at that distance. The results give a core mass of 7 Earth masses and an envelope mass of approximately 0.1 Earth mass after 500,000 years, at which point the envelope growth rate surpasses that of the core. The same calculation without the envelope gives a core mass of only 4 Earth masses.
    Keywords: Astronomy
    Type: ARC-E-DAA-TN10762 , NCTS# 16972-14; Annual Meeting, Division for Planetary Science; Oct 06, 2013 - Oct 11, 2013; Denver, CO; United States
    Format: application/pdf
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  • 9
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    DP Capabilities: LWA Current and Future Users Meeting (2011)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: No abstract available
    Keywords: Astronomy
    Type: LWA Current and Future Users Meeting; May 12, 2011 - May 13, 2011; Albuquerque, NM; United States
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  • 10
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    A FPGA-based Fast Transient Search Platform for the Australian Square Kilometre Array Pathfinder (2011)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: No abstract available
    Keywords: Astronomy
    Type: National Radio Science Meeting (USNC-URSI); Jan 05, 2011 - Jan 09, 2011; Boulder, CO; United States
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