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

Investigations on physics and dynamics of matter with the Karlsruhe Light Ion Facility KALIF

In this report we present investigation on the dense plasma performed in the last few years at our light ion facility KALIF. Equation of state of matter in the region of strongly coupled plasma is investigated. The zone directly heated by the KALIF beam gets about 5 MJ/g of energy within first few 10's of ns. This launches a strong shock wave in the adjacent cold material. By suitably designing the target thin foils could be accelerated to velocities >12 km/s. The acceleration of flyer plate is not monotonic and shows several steps caused by shock wave reverberation within the flyer. Detailed analysis of this process gives clues about the equation of state of the matter. We have developed a Mie-Grueneisen type of equation of state that describe states of matter better than the previously available equation of states. Precise measurement of shock melting for a few materials is also presented. Further, spall strengths for some single- and polycrystalline materials have been measured at high strain rates in excess of 10"6s"-"1. Spall strength of single crystals exceed that of polycrystalline material by a factor of 2 to 3. (orig.)86 refs.Available from TIB Hannover: ZA 5141(5991) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman