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  • 1
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    Unknown
    In:  Other Sources
    Publication Date: 2011-08-18
    Description: Variations in the Mg II 2800-A doublet of Zeta Aurigae have been observed. The Mg II profiles deviate from simple P-Cygni profiles in that they exhibit an absorption feature consistent with Chapman's (1981) interpretation of C IV absorption as evidence of a column of accretion onto the B-star component of the binary. The opening angle of the shock cone containing the accretion column is found to exceed 16 deg, implying a stellar wind velocity of approximately 67 km/s, unless the H II region temperature is unusually high. The turbulence velocity of the wind then appears to be about 33 km/s, compared to values of order 10 km/s previously determined closer to the K-star surface.
    Keywords: ASTROPHYSICS
    Type: Astronomy and Astrophysics (ISSN 0004-6361); 126; 2, Oc
    Format: text
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  • 2
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    In:  Other Sources
    Publication Date: 2019-07-12
    Description: Archival IUE observations of 31 Cygni at phases at which its sister Zeta Aurigae systems exhibit evidence of an accretion wake are discussed. The absence of absorption in Mg II can be explained by the phase at the specific times of observation. The detection of high-velocity absorption due to C IV but not N V implies a shock temperature lower than that of Zeta Aur and 22 Vul but higher than than of 32 Cygni. The dependence of the high-velocity absorption component on phase is consistent with a simple model for the shock structure. The reverse P Cygni profiles in the high-temperature lines are weak and the emission components are observed only at the times when the accretion shock cone absorption is detected. Interpretation of a high-velocity shortward-shifted absorption component as circumstellar material is consistent with the estimated terminal velocity of the supergiant wind.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 338; 1011-101
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  • 3
    Publication Date: 2019-07-12
    Description: A semiempirical model for the wind in four Zeta Aur binary systems is developed, basing the analyses on the velocity function, nonthermal velocities, and upper limits to Ne/N(H) inferred from observations of the winds from the cool supergiants. The model assumes that the energy fluxes needed to drive the wind are supplied by Alfven waves, since the acoustic wave flux estimated from line broadening is too low. The damping scale length of the waves, is found to change from very small values near the star to larger values of the order of the local radius further out in the wind. The temperature structure and hydrogen ionization are derived for these models. Limits to the stellar magnetic field are found, as well as a necessary constraint for the existence of cool massive winds, suggesting that the dividing line in the H-R diagram is where this constraint is violated.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 344; 856-869
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  • 4
    Publication Date: 2019-07-12
    Description: The existence of an accretion column in 32 Cyg is reported, and the presence of the accretion column in Zeta Aurigae is confirmed. Secular variations have been detected for Zeta Aur. Refinements are suggested for the model of Ahmad, Chapman, and Kondo (1983). Resonance line equivalent widths have been calculated and the implications for flow geometry, secular variability, and plasma density are discussed.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 301; 275-285
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  • 5
    Publication Date: 2019-07-12
    Description: A previous report that 22 Vul is a zeta Aurigae-type eclipsing binary is supported by the discovery of evidence for an accretion shock cone in 22 Vul similar to those found in zeta Aurigae and 32 Cygni. Such systems consist of a cool supergiant star primary and a hot dwarf secondary (G3 Ib-II and B9 in the case of 22 Vul) and undergo atmospheric eclipses.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters to the Editor (ISSN 0004-637X); 299; L33-L35
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