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  • Other Sources  (14)
  • 1
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    Balmer-line-blanketed model atmospheres for A- type stars. (1966)
    In:  Other Sources
    Details
    Publication Date: 2019-05-30
    Description: Grid computations of model atmospheres for A-type stars, considering effects of Balmer-line blanketing
    Keywords: SPACE SCIENCES
    Type: ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES
    Format: text
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  • 2
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    A model for a b1 v star with line blanketing. (1965)
    In:  Other Sources
    Details
    Publication Date: 2019-05-24
    Description: B1 V star model atmosphere calculated and iterated for flux constancy, considering blanketing by strongest lines in UV
    Keywords: SPACE SCIENCES
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  • 3
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    The acceleration and propagation of solar flare energetic particles (1982)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Observations and theories of particle acceleration in solar flares are reviewed. The most direct signatures of particle acceleration in flares are gamma rays, X-rays and radio emissions produced by the energetic particles in the solar atmosphere and energetic particles detected in interplanetary space and in the Earth's atmosphere. The implication of these observations are discussed. Stochastic and shock acceleration as well as acceleration in direct electric fields are considered. Interplanetary particle propagation is discussed and an overview of the highlights of both current and promising future research is presented.
    Keywords: SOLAR PHYSICS
    Type: NASA-TM-83989 , NAS 1.15:83989
    Format: application/pdf
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  • 4
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    Resonance-line transfer with partial redistribution. VIII - Solution in the comoving frame for moving atmospheres (1976)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: The effects of partial frequency redistribution in the scattering process for lines formed in moving atmospheres are analyzed using a general method that allows the transfer equation to be solved in the comoving frame of the gas. The same chromospheric and atomic model studied by Cannon and Vardavas (1974) is employed in the calculations, but a depth scale with logarithmically spaced points is adopted. It is found that in both static and moving atmospheres, the profiles obtained with complete and partial frequency redistribution are virtually identical. The large differences in profiles obtained by Cannon and Vardavas when they used complete and partial redistribution are shown to be spurious (and physically unreal) effects resulting from angle averaging in the observer's frame instead of the comoving frame.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; 205; Apr. 15
    Format: text
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  • 5
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    Theoretical helium I emission-line intensities for quiescent prominences (1974)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: Self-consistent solutions of the combined statistical equilibrium and transfer equations have been carried out for a rather complete multilevel, multi-ion model helium atom in model quiescent prominences. The excitation and ionization of both He I and He II were considered simultaneously, and detailed calculations of the radiative transfer in the resonance lines and ground-state continua of both these ions were made, allowing for the effects of overlapping hydrogen transitions. A large number of excited states have been included in the computation, so that a fairly comprehensive set of predicted subordinate line intensities are now available for comparison with observation. A preliminary comparison of the predicted values with published singlet/triplet ratio observations shows good agreement for all the pairs of lines considered.
    Keywords: SPACE SCIENCES
    Type: Astrophysical Journal; 192; Aug. 15
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  • 6
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    Resonance line transfer with partial redistribution. IV - A generalized formulation for lines with common upper states. V - The solar Ca II lines (1975)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: A generalized formulation is given for treating partial redistribution effects in transfer problems in resonance lines with common upper states. The formulation allows explicitly for the possibility that several spectral lines may arise in transitions from a given upper level to several sharp lower levels, including, for example, the ground state and metastable states. Line profiles for the Ca II H and K lines have been calculated, accounting for the partial frequency coherence of scattered photons. These profiles are compared with calculations made with identical atomic and atmospheric models but assuming complete redistribution. Very significant differences between the profiles obtained using these two different physical descriptions of the scattering process are found, and it is now apparent that the assumption of complete redistribution is a serious oversimplification of the actual physical situation. The results question the validity of equating brightness temperatures observed at K(sub 1) in stellar spectra with minimum temperatures in stellar chromospheres; it appears likely that such a procedure will systematically underestimate the value of T-min.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal; 199; Aug. 1
    Format: text
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  • 7
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    Resonance line transfer with partial redistribution. VI - The Ca II K-line in solar-type stars (1975)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; 201; Oct. 1
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  • 8
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    He I lambda 4922 profiles in B stars - Calculations with an improved line broadening theory (1975)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; 197; Apr. 1
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  • 9
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    The photometric variability of solar-type stars. III - Results from 1981-82, including parallel observations of thirty-six Hyades stars (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: A photometric survey of main-sequence stars in the Pleiades, Hyades, and Malmquist Field, to investigate variability among solar-type stars, had been continued at Cloudcroft Observatory for a second season. Possibly six of 40 Pleiades stars, two (possibly six) of 49 Hyades stars and possibly four of 42 stars in the Malmquist Field are found to be variable. Parallel observations of Hyades stars were obtained also at Lowell Observatory. These measurements, which achieved better precision, reveal significiant variations in eleven (possibly 16) of 36 Hyades stars, all of spectral type F7 V-K2 V. Agreement between the two surveys is acceptable. The two seasons of the Cloudcroft survey show that changes in the mean annual brightness of the Hyades stars accompany changes in the amplitude of their short-term variability, in the sense that a star tends to become fainter as its variability increases and vice versa. Color effects are absent.
    Keywords: ASTROPHYSICS
    Type: AD-A135037 , AFGL-TR-83-0303 , Astronomical Society of the Pacific, Publications (ISSN 0004-6280); 95; 621-634
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  • 10
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    An archetype hydrogen atmosphere problem (1975)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: Populations for the first three bound states and the continuum of hydrogen are determined for an isothermal hydrostatic atmosphere at 20,000 K. The atmosphere is treated as optically thin in the Balmer and Paschen continua and illuminated by continuum radiation at these wavelengths with prescribed radiation temperatures. The atmosphere is optically thick in the 2-1, 3-1, 3-2 and c-1 transitions. Three stages of approximation are treated: (1) radiative detailed balance in the 2-1, 3-1 and 3-2 transitions, (2) radiative detailed balance in the 3-1 and 3-2 transitions, and (3) all transitions out of detailed balance. The solution of this problem is nontrivial and presents sufficient difficulty to have caused the failure of at least one rather standard technique. The problem is thus a good archetype against which new methods or new implementations of old methods may be tested.
    Keywords: ASTROPHYSICS
    Type: Solar Physics; 45; Nov. 197
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