Masses, Oxygen and Carbon abundances in CHEPS dwarf stars

Reproduced with permission from Astronomy & Astrophysics. © 2019 ESOContext. We report the results from the determination of stellar masses, carbon, and oxygen abundances in the atmospheres of 107 stars from the Calan-Hertfordshire Extrasolar Planet Search (CHEPS) programme. Our stars are drawn from a population with a significantly super-solar metallicity. At least 10 of these stars are known to host orbiting planets. Aims. In this work, we set out to understand the behaviour of carbon and oxygen abundance in stars with different spectral classes, metallicities, and V sin i within the metal-rich stellar population. Methods. Masses of these stars were determined using data from Gaia DR2. Oxygen and carbon abundances were determined by fitting the absorption lines. We determined oxygen abundances with fits to the 6300.304 Å O I line, and we used 3 lines of the C I atom and 12 lines of the C 2 molecule for the determination of carbon abundances. Results. We determine masses and abundances of 107 CHEPS stars. There is no evidence that the [C/O] ratio depends on V sin i or the mass of the star within our constrained range of masses, i.e. 0.82 5 km s -1) are massive stars.Peer reviewedFinal Published versio

Extended Kalman Filter for Photographic Data from Impact Acceleration Tests

This paper presents the development of an Extended Kalman Filter (EKF) that optimally processes photographic data collected during short-duration impact acceleration tests. The system is modeled by a non-linear state-space representation using quaternions for rotational kinematics. Three cameras are used to photograph up to 14 fiducials mounted on a plate attached to the subject\u27s mouth. The filter yields the history of the rotational and translational kinematics of the origin of the mouth plate. Results from the EKF and analysis of the estimation error are presented

The determinants of vulnerability to currency crises: country-specific factors versus regional factors

We investigate the determinants of exchange market pressures (EMP) for some new EU member states at both the national and regional levels, where macroeconomic and financial variables are considered as potential sources. The regional common factors are extracted from these variables by using dynamic factor analysis. The linear empirical analysis, in general, highlights the importance of country-specific factors to defend themselves against vulnerability in their external sectors. Yet, given a significant impact of the common component in credit on EMP, a contagion effect is apparent through the conduit of credit market integration across these countries under investigation

Uncertainty-principle noise in vacuum-tunneling transducers

The fundamental sources of noise in a vacuum-tunneling probe used as an electromechanical transducer to monitor the location of a test mass are examined using a first-quantization formalism. We show that a tunneling transducer enforces the Heisenberg uncertainty principle for the position and momentum of a test mass monitored by the transducer through the presence of two sources of noise: the shot noise of the tunneling current and the momentum fluctuations transferred by the tunneling electrons to the test mass. We analyze a number of cases including symmetric and asymmetric rectangular potential barriers and a barrier in which there is a constant electric field. Practical configurations for reaching the quantum limit in measurements of the position of macroscopic bodies with such a class of transducers are studied

Near-Infrared water lines in V838 Monocerotis

V838 Monocerotis had an intriguing, nova-like outburst in January 2002 which has subsequently led to several studies of the object. It is now recognized that the outburst of V838 Mon and its evolution are different from that of a classical nova or other classes of well-known eruptive variables. V838 Mon, along with two other objects that have analogous properties, appears to comprise a new class of eruptive variables. There are limited infrared studies of V838 Mon. Here, we present near-infrared H band (1.5 - 1.75micron) spectra of V838 Mon from late 2002 to the end of 2004. The principal, new result from our work is the detection of several, rotation-vibration lines of water in the H band spectra. The observed water lines have been modeled to first establish that they are indeed due to water. Subsequently the temperature and column densities of the absorbing material, from where the water absorption features originate, are derived. From our analysis, we find that the water features arise from a cool ~750-900 K region around V838 Mon which appears to be gradually cooling with time.Comment: 11 pages, 2 figures. Accepted in Ap.J Letter

Effective Lorentz Force due to Small-angle Impurity Scattering: Magnetotransport in High-Tc Superconductors

We show that a scattering rate which varies with angle around the Fermi surface has the same effect as a periodic Lorentz force on magnetotransport coefficients. This effect, together with the marginal Fermi liquid inelastic scattering rate gives a quantitative explanation of the temperature dependence and the magnitude of the observed Hall effect and magnetoresistance with just the measured zero-field resistivity as input.Comment: 4 pages, latex, one epsf figure included in text. Several revisions and corrections are included. Major conclusions are the sam

A detailed study of Lithium in 107 CHEPS dwarf stars

Reproduced with permission from Astronomy & Astrophysics, © ESO 2018.Context. We report results from lithium abundance determinations using high resolution spectral analysis of the 107 metal-rich stars from the Calan-Hertfordshire Extrasolar Planet Search programme. Aims. We aim to set out to understand the lithium distribution of the population of stars taken from this survey. Methods. The lithium abundance taking account of non-local thermodynamical equilibrium effects was determined from the fits to the Li I 6708 Å resonance doublet profiles in the observed spectra. Results. We find that a) fast rotators tend to have higher lithium abundances; b) log N(Li) is higher in more massive and hot stars; c) log N(Li) is higher in stars of lower log g; d) stars with the metallicities >0.25 dex do not show the lithium lines in their spectra; e) most of our planet hosts rotate slower; and f) a lower limit of lithium isotopic ratio is 7Li/ 6Li > 10 in the atmospheres of two stars with planets (SWP) and two non-SWP stars. Conclusions. Measurable lithium abundances were found in the atmospheres of 45 stars located at distances of 20-170 pc from the Sun, for the other 62 stars the upper limits of log N(Li) were computed. We found well defined dependences of lithium abundances on T eff, V sin i, and less pronounced for the log g. In case of V sin i we see two sequences of stars: with measurable lithium and with the upper limit of log N(Li). About 10% of our targets are known to host planets. Only two SWP have notable lithium abundances, so we found a lower proportion of stars with detectable Li among known planet hosts than among stars without planets. However, given the small sample size of our planet-host sample, our analysis does not show any statistically significant differences in the lithium abundance between SWP and stars without known planets.Peer reviewe