36 research outputs found

    Horizontal Branch Stars: The Interplay between Observations and Theory, and Insights into the Formation of the Galaxy

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    We review HB stars in a broad astrophysical context, including both variable and non-variable stars. A reassessment of the Oosterhoff dichotomy is presented, which provides unprecedented detail regarding its origin and systematics. We show that the Oosterhoff dichotomy and the distribution of globular clusters (GCs) in the HB morphology-metallicity plane both exclude, with high statistical significance, the possibility that the Galactic halo may have formed from the accretion of dwarf galaxies resembling present-day Milky Way satellites such as Fornax, Sagittarius, and the LMC. A rediscussion of the second-parameter problem is presented. A technique is proposed to estimate the HB types of extragalactic GCs on the basis of integrated far-UV photometry. The relationship between the absolute V magnitude of the HB at the RR Lyrae level and metallicity, as obtained on the basis of trigonometric parallax measurements for the star RR Lyrae, is also revisited, giving a distance modulus to the LMC of (m-M)_0 = 18.44+/-0.11. RR Lyrae period change rates are studied. Finally, the conductive opacities used in evolutionary calculations of low-mass stars are investigated. [ABRIDGED]Comment: 56 pages, 22 figures. Invited review, to appear in Astrophysics and Space Scienc

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    227 hal . ; 21 cm

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    Revisiting Wilkins' 'Notional syllabuses'.

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    One of the innovations that we have recently introduced in our reviews section is to include reviews of books that were published some time ago. The aim of the ‘classics’ reviews is to indicate how far these older works are still relevant to current thinking, how far we have or have not moved on, and generally to serve as an occasion for a critical reappraisal. The intention is to publish these reviews on a significant anniversary of the original publication, and as 2006 is the 30th anniversary of David Wilkins's Notional Syllabuses, we have asked Keith Johnson to launch the series with a review of this book
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