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

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

Social influence by artefacts

A review of the paradigms of social influence – suggestion, imitation, normalization, conformity, compliance, conversion – leads me to diagnose a triple malaise: the shrinkage of paradigms to cognitive dual-processing theories of information; the dominant methodology of laboratory experiments falls short of the reality of (mass) communication; and the focus of social influence on inter-subjectivity is only half of the story. I will suggest two extensions of social influence theory to include mass media communication and the inter-objectivity of artefacts. We need to be able to conceptualize the modalities of why, how and to what effect somebody might put up a wall to influence neighbours instead of contenting themselves with putting up a public note ‘Do not trespass!’. Social influence by fait accompli needs to be within the remit of social psychology, otherwise it loses its relevance in a technological society where artefacts mediate most inter-personal relations