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  • 1
    Publication Date: 2011-08-19
    Description: The line fluxes of the C IV 1550 A and semiforbidden C III 1909 A emission lines in HH 1 are noted to have monotonically decreased by factors of 4-6 between 1979 and 1983, despite a lack of indications of optical range changes. The thickness of the shocked layers and preshock density can be estimated on the basis of these rapid changes, with results suggesting a clumpy medium that leads to truncated shock waves with column densities insufficient for the development of complete recombination zones.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters to the Editor (ISSN 0004-637X); 292; L75-L78
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  • 2
    Publication Date: 2011-08-18
    Description: Short- and long-wavelength IUE spectra of the rather strongly reddened, high radial velocity Herbig-Haro object HH 32A have been obtained. The object is well known for its large positive radial velocity and for its unusually large velocity dispersion. In consequence of the large ultraviolet extinction, the spectra are faint. The semiforbidden C III 1909 and Mg II 2800 emission lines are, however, clearly detected, and their fluxes can be measured with reasonable accuracy. C IV 1550 and Si III 1892 are very probably present. The continuum can be detected convincingly in the wavelength range 1500-1900 A. In other regions it is just barely detectable. The continuum has an energy distribution which is probably very similar to that of HH 1 and HH 2H. If an average galactic extinction curve is used, the line fluxes for semiforbidden C III 1909 and C IV 1550 indicate a shock velocity of at least 140 km/s which is higher than for HH 1 or HH 2. If a Theta Ori-type extinction curve is used instead, ultraviolet line ratios are obtained which are rather similar to those in HH 1 and HH 2.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 277; 216-219
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  • 3
    Publication Date: 2011-08-18
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 263
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  • 4
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    Publication Date: 2011-08-19
    Description: The characteristics of intrinsically variable stars are examined, reviewing the results of observations obtained with the IUE satellite since its launch in 1978. Selected data on both medium-spectral-class pulsating stars (Delta Cep stars, W Vir stars, and related groups) and late-type variables (M, S, and C giants and supergiants) are presented in spectra, graphs, and tables and described in detail. Topics addressed include the calibration of the the period-luminosity relation, Cepheid distance determination, checking stellar evolution theory by the giant companions of Cepheids, Cepheid masses, the importance of the hydrogen convection zone in Cepheids, temperature and abundance estimates for Population II pulsating stars, mass loss in Population II Cepheids, SWP and LWP images of cold giants and supergiants, temporal variations in the UV lines of cold stars, C-rich cold stars, and cold stars with highly ionized emission lines.
    Keywords: ASTROPHYSICS
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  • 5
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    Publication Date: 2011-08-19
    Description: The absolute visual magnitudes of main-sequence Cepheid companions are here determined from their effective temperatures. The latter are obtained by comparing the measured relative energy distributions with model atmosphere energy distributions. Assuming an average Galactic extinction law, it is found that the distance moduli for the Cepheids should be smaller by Delta (mv-Mv) = -0.5 as compared to the Sandage-Tammann relation.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 296; 169-174
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  • 6
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    Publication Date: 2011-08-19
    Description: Twenty-one Cepheids, known or suspected to have blue companions, were studied with the International Ultraviolet Explorer satellite. For 13 of them, companions were indeed seen, though they were generally fainter in the UV than expected. For four Population I Cepheids, the suspected companions were not seen. For none of the Population II Cepheids could a companion be detected. The effective temperatures and luminosities of the companions which could be observed are discussed, and the positions of Cepheids and companions in the T(eff) luminosity diagrams are compared with positions expected from stellar evolution calculations.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 296; 175-184
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  • 7
    Publication Date: 2011-08-19
    Description: The ultraviolet energy distributions of the B stars in the LMC cluster NGC 2100 have been studied. The ultraviolet extinction law was studied for the LMC cluster. The T(eff)-luminosity diagrams were determined. The brightest stars in the cluster are evolved stars on the 'horizontal' supergiant branch. No P Cygni profiles indicating mass loss were recognized for these supergiants.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 292; 130-142
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  • 8
    Publication Date: 2011-08-19
    Description: In the present paper, the observation of a white dwarf companion of the mild Ba star Xi-1 Ceti (= 65 Ceti = HR 649 = HD 13611) is reported, taking into account also the properties of the mild Ba star and of its companion. The UV spectrum of Xi-1 Ceti is discussed along with an interpretation of this spectrum. Attention is given to the effective temperature of the companion, the absorption bands in the spectrum, the radius and mass of the Xi-1 Ceti companion, and questions regarding the obscuration of the companion by the atmosphere of the Ba star. It is found that the overall energy distribution of the Xi-1 Ceti companion can best be matched with a 14,000 K DA white dwarf of log g = 8 or less. However, the absolute intensity is too small and would require a radius too small and a mass too large for such a gravity.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 293; 288-293
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  • 9
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    Publication Date: 2011-08-18
    Description: Ultraviolet observations of barium stars and other cool stars with peculiar element abundances are reported. Those observations attempted to find hot white dwarf companions. Among six real barium stars studied, only Zeta Cap was found to have a white dwarf companion. Among seven mild, or marginal, barium stars studied, at least three were found to have hot subluminous companions. It is likely that all of them have white dwarf companions.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 278; 726-738
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  • 10
    Publication Date: 2011-08-19
    Description: The discrepancy noted in radii obtained by the Baade-Wesselink method when different colors are used to determine the effective temperatures is explored. The discrepancy is found to be due to an inconsistency in the applied temperature-color calibrations. The assumption of the maximum likelihood method that beta (the effective temperature + 0.1 times the bolometric correction) is a linear function of the color is valid for the B-V and V-I colors, but not for the V-R colors. It is suggested that the errors introduced by the nonlinearity in the relation between beta and the V-R colors will produce radii which are too large. The radii derived from the V-B colors appear to be too small.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 343; 343-351
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