Yazar "Blackford, M." seçeneğine göre listele

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    Absolute parameters of young stars: GG Lup and ?1 Sco
    (Oxford Univ Press, 2015) Budding, E.; Butland, R.; Blackford, M.
    New high-resolution spectroscopy and BVR photometry, together with literature data, on the Gould's Belt close binary systems GG Lup and mu(1) Sco are presented and analysed. In the case of GG Lup, light and radial velocity curve fittings confirm a near-main-sequence picture of a pair of close stars. Absolute parameters are found, to within a fewper cent, thus: M-1 = 4.16 +/- 0.12, M-2 = 2.64 +/- 0.12 (M-circle dot); R-1 = 2.42 +/- 0.05, R-2 = 1.79 +/- 0.04 (R-circle dot); T-1 similar to 13 000, T-2 similar to 10 600 (K); photometric distance similar to 160 (pc). The high eccentricity and relatively short period (105 yr) of apsidal revolution may be related to an apparent 'slow B-type pulsator' oscillation. Disturbances of the outer envelope of at least one of the components then compromise comparisons to standard evolutionary models, at least regarding the age of the system. A rate of apsidal advance is derived, which allows a check on the mean internal structure constant (k(2)) over bar +/- 0.0058 +/- 0.0004. This is in agreement with values recently derived for young stars of solar composition and mass similar to 3 M-circle dot. For mu(1) Sco, we agree with previous authors that the secondary component is considerably oversized for its mass, implying binary (interactive) stellar evolution, probably of the ` Case A' type. The primary appears relatively little affected by this evolution, however. Its parameters show consistency with a star of its derived mass at age about 13 Myr, consistent with the star's membership of the Sco-Cen OB2 Association. The absolute parameters are as follows: M-1 = 8.3 +/- 1.0, M-2 = 4.6 +/- 1.0 (M circle dot); R-1 = 3.9 +/- 0.3, R-2 = 4.6 +/- 0.4 (R-circle dot); T-1 +/- 24 000, T-2 +/- 17 000 (K); photometric distance similar to 135 (pc).
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    Absolute parameters of young stars: QZ Carinae
    (Oxford Univ Press, 2017) Walker, W. S. G.; Blackford, M.; Butland, R.; Budding, E.
    New high-resolution spectroscopy and BVR photometry together with literature data on the complex massive quaternary star QZ Car are collected and analysed. Absolute parameters are found as follows. System A: M-1 = 43 (+/- 3), M-2 = 19 (+3 -7), R-1 = 28 (+/- 2), R-2 = 6 (+/- 2), (circle dot); T-1 similar to 28 000, T-2 similar to 33 000 K; System B: M-1 = 30 (+/- 3), M-2 = 20 (+/- 3), R-1 = 10 (+/- 0.5), R-2 = 20 (+/- 1), (circle dot); T-1 similar to 36 000, T-2 similar to 30 000 K (model dependent temperatures). The wide system AB: Period = 49.5 (+/- 1) yr, Epochs, conjunction = 1984.8 (+/- 1), periastron = 2005.3 (+/- 3) yr, mean separation = 65 (+/- 3), (au); orbital inclination = 85 (+5 - 15) deg, photometric distance similar to 2700 (+/- 300) pc, age = 4 (+/- 1) Myr. Other new contributions concern: (a) analysis of the timing of minima differences (O - C) s for the eclipsing binary (System B); (b) the width of the eclipses, pointing to relatively large effects of radiation pressure; (c) inferences from the rotational widths of lines for both Systems A and B; and (d) implications for theoretical models of early-type stars. While feeling greater confidence on the quaternary's general parametrization, observational complications arising from strong wind interactions or other, unclear, causes still inhibit precision and call for continued multiwavelength observations. Our high-inclination value for the AB system helps to explain failures to resolve the wide binary in the previous years. The derived young age independently confirms membership of QZ Car to the open cluster Collinder 228.
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    Collaborative Studies of Southern Close Binary Systems
    (Astronomical Soc Pacific, 2015) Budding, E.; Blackford, M.; Butland, R.; Demircan, O.; Erdem, A.; Idaczyk, R.; Ozkardes, B.
    We present a few items from our southern eclipsing binary program, underway in recent years and involving observations at the Mt. John University Observatory and elsewhere in Australasia. Reduction and analysis have also been carried out at COMU (Turkey). Derived parameters allow interesting comparisons with other recent findings on binary stars, observational and theoretical.