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  • ASTROPHYSICS  (7)
  • Acoustics
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  • 1
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    Intercontinental antenna arraying by symbol stream combining at ICE Giacobini-Zinner encounter (1986)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Deep space tracking stations on different continents were arrayed during the encounter of the International Cometary Explorer (ICE) spacecraft with the comet Giacobini-Zinner during September 9 through 12, 1985. This is the first time that telemetry signals received on different continents have been combined to enhance signal to noise ratio. The arraying was done in non-real time using the method of symbol stream combining. The improvement in signal to noise ratio was typically 2 dB over the stronger of the two stations in each array.
    Keywords: ASTROPHYSICS
    Type: The Telecommunications and Data Acquisition Report; p 220-228
    Format: application/pdf
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  • 2
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    RE 0044+09: A new K dwarf rapid rotator with a white dwarf companion (1995)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: We report the discovery of a new K dwarf rapid rotator with a potential white dwarf companion. The white dwarf accounts for over 90% of the observed extreme ultraviolet flux detected from this system. Analysis of ROSAT Wide Field Camera (WFC) and IUE data both suggest a white dwarf temperature of approximately 28,700 K. Optical photometry and the IUE long wavelength prime (LWP) spectrum (with the white dwarf contribution removed) imply that the late-type star has a spectral type of K1-3 V, and a distance of 55 +/- 5 pc. Using this distance, the observed IUE SWP flux, and the best-fit temperature results in a white dwarf radius of 0.0088 solar radius. The estimated white dwarf mass is then approximately 0.91 solar mass; somewhat over-massive compared to field white dwarfs. Optical photometry of the K star reveals a 'spot' modulation period of approximately 10 hr (now observed over 3 yr). However, radial velocity observations have revealed no significant variations. Spectroscopic observations place a low limit on the lithium abundance, but do show rapid rotation with a v sin i of 90 +/- 10 km/s. The K star was detected as a radio source at 3.6 cm (on two occasions) and 6 cm by the Very Large Array (VLA). The most likely evolutionary scenario is that the K star and hot white dwarf from either a wide binary or common proper motion pair with an age of 0.1-0.1 Gyr-consistent with the evolutionary timescale of the white dwarf and the rapid rotation of the K star. However, from the proper motion of the K star, this system does not seem to be associated with any of the known young stellar groups.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 438; 1; p. 364-375
    Format: text
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  • 3
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    RJ 051542+0104.7: A new magnetic, eclipsing, cataclysmic variable (1994)
    In:  Other Sources
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    Publication Date: 2019-08-28
    Description: We present photometric and spectroscopic observations of a recently identified X-ray bright, magnetic cataclysmic variable, RJ 051542+0104.7. The X-ray source was discovered serendipitously by Walter et al. (1994; Walter & Zoonematkermani 1994), and their data imply the presence of a heated white dwarf compatible with a magnetic accretion column. Buckley (1994) has reported the presence of circular polarization. Our optical photometry shows that the system undergoes eclipses with a period of 7.9835 +/- 0.0002 hours. The eclipse is 1 magnitude deep and appears to be total. Our spectra were all obtained near eclipse and show a strong blue continuum with broad Balmer emission as well as He II (4686 and 5411 A), C III/N III (4650 A) and He I lines. The blue continuum and emission lines disappear during eclipse, leaving only the spectrum of a M0 star. Using the observed magnitude during eclipse and ignoring interstellar extinction, the distance is approximately 500 pc. For the secondary to fill its Roche lobe, it must be at least 20% larger than that of a normal dM0 star. This may indicate the red dwarf is far from local thermodynamic equilibrium (LTE) due to strong magnetic braking. We find evidence for cyclotron humps in the continuum spectrum which imply a magnetic field strength in the cyclotron emitting region of up to 55 MG. The unexpected existence of a long period AM Her system should provide constraints on models of polar evolution.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters (ISSN 0004-637X); 435; 2; p. L141-L144
    Format: text
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  • 4
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    Testing models of low-mass star formation - High-resolution far-infrared observations of L1551 IRS 5 (1991)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: A 50 and 100 micron wavelength study of L151 IRS 5 has yielded data consistent with the Adams et al. (1987) theoretical model prediction. It has proven possible to constrain a range of possible density gradients through source-emission modeling on the basis of the spherically-symmetric radiative transfer program of Egan et al. (1988) and a comparison of the observed scans at 50 and 100 microns. Attention is given to the effects of varying the dust grain properties of the spherical energy distribution of the source; the amount of mid-IR emission is highly sensitive to dust opacity and, because of poorly understood dust properties, is not a sensitive test for the presence of disks.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 376; 636-653
    Format: text
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  • 5
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    Conservative Overset Grids for Overflow For The Sonic Wave Atmospheric Propagation Project (1999)
    In:  CASI
    Details
    Publication Date: 2019-07-10
    Description: Methods are presented that can be used to make multiple, overset grids communicate in a conservative manner. The methods are developed for use with the Chimera overset method using the PEGSUS code and the OVERFLOW solver.
    Keywords: Acoustics
    Format: application/pdf
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  • 6
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    Molecular outflows and mass loss in the pre-main-sequence stars (1988)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: Molecular outflows are used here to probe mass loss in premain sequence (PMS) stars. Mass-loss rates are determined for 26 objects ranging in luminosity from four to about 100,000 solar, in mass from 0.5 to 30 solar, and in age from about 10,000 to about a million years. The derived mass-loss rates range from 9 x 10 to the -9th to 9 x 10 to the -4th solar mass/yr, with a typical value of 3 x 10 to the -7th solar mass/yr. PMS objects showing mass loss fall in a clearly demarcated region of the H-R diagram. The mass loss is proportional to bolometric luminosity to the 0.6 power and to stellar mass to the 1.8 power. The implications of these findings for the nature of the PMS mass-loss mechanism, for self-regulated low-mass star formation, and for planetary formation are discussed.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 330; 897-910
    Format: text
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  • 7
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    A search for molecular outflows toward the pre-main-sequence objects (1988)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: A search for molecular outflows has been conducted toward a sample of 71 young stellar objects dominated by optically selected pre-main-sequence stars. Molecular outflows ranging in size from 0.07 to about 5 pc, with expansion velocities from 6 to 60 km/s, have been detected toward 20 of these objects and in an additional six infrared objects not included in the original survey. The apparent ages of the outflows are from 1000 to 500,000 yr; about half of the observed outflows are bipolar, with the rest showing a wide variety of morphologies. It is found that outflows driven by low-luminosity objects tend to be more bipolar than those driven by high-luminosity objects. The implications of the results of the study are discussed.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal Supplement Series (ISSN 0067-0049); 67; 283-371
    Format: text
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  • 8
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    The spectrum of random magnetic fields in the mean field dynamo theory of the Galactic magnetic field (1992)
    In:  Other Sources
    Details
    Publication Date: 2019-08-27
    Description: The fluctuation spectrum that must arise in a mean field dynamo generation of galactic fields if the initial field is weak is considered. A kinetic equation for its evolution is derived and solved. The spectrum evolves by transfer of energy from one magnetic mode to another by interaction with turbulent velocity modes. This kinetic equation is valid in the limit that the rate of evolution of the magnetic modes is slower than the reciprocal decorrelation time of the turbulent modes. This turns out to be the case by a factor greater than 3. Most of the fluctuation energy concentrates on small scales, shorter than the hydrodynamic turbulent scales. The fluctuation energy builds up to equipartition with the turbulent energy in times that are short compared to the e-folding time of the mean field. The turbulence becomes strongly modified before the dynamo amplification starts. Thus, the kinematic assumption of the mean dynamo theory is invalid. Thus, the galactic field must have a primordial origin, although it may subsequently be modified by dynamo action.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 396; 2 Se
    Format: text
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