Pottery firing temperatures: A new method for determining the firing temperature of ceramics and burnt clay

A new method for determining the maximum firing temperature of ceramics and burnt clay is presented. The technique relies on measuring the magnetic susceptibility on a step-wise re-fired sample. The validity of the method has been tested by determining firing temperatures of two sets of clay samples fired at temperatures ranging from 400 to 1000 C. Aliquots of the same samples have been studied petrographically by optical microscopy on thin sections and analyzed by powder X-ray diffraction in order to monitor structural and mineralogical changes as a function of temperature. The method is demonstrated on samples from four geographically widely different sites and it is applied to a larger set of ceramics of Late (ca. AD 900eAD 1450) and Inca (ca. AD 1480eAD 1532) periods from the Northwestern Argentine region, dating to a limited period of time prior to the fall of the Inca Empire. The method is shown to be a powerful tool in revealing archaeological information about the change in firing technologies in the pre-Hispanic societies in the Andean area through time.Fil: Rasmussen, Kaare Lund. Technical University of Denmark; DinamarcaFil: de la Fuente, Guillermo Adrian. Universidad Nacional de Catamarca. Escuela de Arqueología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Bond, Andrew D.. Technical University of Denmark; DinamarcaFil: Mathiesen, Karsten Korsholm. Technical University of Denmark; DinamarcaFil: Vera, Sergio David. Universidad Nacional de Catamarca. Escuela de Arqueología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Establishing the accuracy of asteroseismic mass and radius estimates of giant stars. II. Revised stellar masses and radii for KIC 8430105

Asteroseismic scaling relations can provide high-precision measurements of mass and radius for red giant (RG) stars displaying solar-like oscillations. Their accuracy can be validated and potentially improved using independent and accurate observations of mass, radius, effective temperature and metallicity. We seek to achieve this using long period SB2 eclipsing binaries hosting oscillating RGs. We explore KIC 8430105, for which a previous study found significant asteroseismic overestimation of mass and radius when compared with eclipsing binary measurements. We measured dynamical masses and radii for both components to be significantly lower than previously established, increasing the discrepancy between asteroseismic and dynamical measurements. Our dynamical measurements of the RG component were compared to corresponding measurements of mass and radius using asteroseismic scaling relations. Uncorrected scaling relations overestimated the mass of the RG by 26%, the radius by 11%, and the average density by 7%, in agreement with studies for other systems. However, using a theoretical correction to $\Delta \nu$, we managed to obtain an asteroseismic average density that is $1\sigma$ consistent with our dynamical result. We obtained several measurements of $\nu_{max}$ that are not fully consistent. With $\nu_{max} = 76.78 \pm 0.81\mu$Hz, the $\Delta \nu$ correction provided $2 \sigma$ consistent mass and radius for the giant. The age of the system was estimated to be $3.7 \pm 0.4$ Gyr

Asteroseismology of the Hyades red giant and planet host epsilon Tauri

Asteroseismic analysis of solar-like stars allows us to determine physical parameters such as stellar mass, with a higher precision compared to most other methods. Even in a well-studied cluster such as the Hyades, the masses of the red giant stars are not well known, and previous mass estimates are based on model calculations (isochrones). The four known red giants in the Hyades are assumed to be clump (core-helium-burning) stars based on their positions in colour-magnitude diagrams, however asteroseismology offers an opportunity to test this assumption. Using asteroseismic techniques combined with other methods, we aim to derive physical parameters and the evolutionary stage for the planet hosting star epsilon Tau, which is one of the four red giants located in the Hyades. We analysed time-series data from both ground and space to perform the asteroseismic analysis. By combining high signal-to-noise (S/N) radial-velocity data from the ground-based SONG network with continuous space-based data from the revised Kepler mission K2, we derive and characterize 27 individual oscillation modes for epsilon Tau, along with global oscillation parameters such as the large frequency separation and the ratio between the amplitude of the oscillations measured in radial velocity and intensity as a function of frequency. The latter has been measured previously for only two stars, the Sun and Procyon. Combining the seismic analysis with interferometric and spectroscopic measurements, we derive physical parameters for epsilon Tau, and discuss its evolutionary status.Comment: 13 pages, 13 figures, 4 tables, accepted for publication in Astronomy & Astrophysic

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