Sökresultat

Estimation of radiation damage to electronics is complex and requires knowledge of several disciplines. Such estimation is important in the assessment of design and construction of systems in radiatory applications. This can be used to approximate the lifetime of electronics and to develop strategies for both ensuring reliability of the equipment and for financial optimization. To understand the i

Observing in the infrared has many benefits, such as seeing through the interstellar dust in the galaxy, easier use of adaptive optics, and better flux ratios for direct observations of exoplanets. Before the infrared spectral range can be utilised for highly accurate stellar spectroscopy there is a need for a better understanding of both stellar modelling and the atomic physics that go into formi

This is a thesis project, analysing data from high-resolution imaging observations, specifically speckle imaging, as a follow up study of exoplanet host stars observed with K2, the second operational phase of the space telescope Kepler. The project was accomplished at NASA Ames research center under the guidance of Rachel A. Matson, during an internship in collaboration with the Swedish National S

Does the formation of planets give imprints on the chemical composition of the host star? In order to test this theory a differential abundance analysis (i.e. comparing two stars' abundances to each other) was carried out on a few stars with and without known planets, to see if any differences were found. The analysis was based on high resolution, high signal to noise ratio (SNR) spectra of fo

Hypervelocity stars (HVSs) are stars located in the Galactic halo travelling with extremely high speeds. They are produced when a binary approches the supermassive black hole (SMBH) in the Galactic Center (GC) and gets tidally broken up. In this process one of the stars is ejected with high velocity. The angle between the velocity of the incoming binary and the velocity of the ejected HVS is alm

Purpose: The purpose of this work is to determine the abundances of neutron-capture elements in solar neighborhood giant stars. This enables constraints to be put on the the cosmic origin of these elements. I have determined abundances of elements produced in both the weak s-process (Cu), the first and second s-process peaks (Y, Zr and La, Ce, Pr, Nd, respectively) and the r-process (Eu, Gd). The

The scientific development of astronomy today mainly comes from the information that can be obtained via electromagnetic radiation. Today, the Gaia optical telescope is one of the most ambitious space projects man has ever completed. Another optical telescope LSST is designed to complement Gaia. In about 15 years it will also be possible to measure gravitational waves with the telescope LISA, whic

Recent work by Nissen and Schuster have found two distinct populations of halo stars with -1<5 alpha [Fe/H] -0<5. Both populations are kinematically selected to be halo stars. The differences between the two groups are the alpha -elemental abundances and the [Na/Fe] and [Ni/Fe] ratios. From angular momentum space, we can see that the majority of these stars do not show any extreme kinematic indica

Detailed abundance analysis of 41 F and G type dwarf stars located in the solar neighborhood are presented. The stellar sample was selected to have kinematics intermediate between the Galactic thin and thick discs. The stars have been observed with the NOT telescope at La Palma, Spain in March 2006 and the ESO 2.2 m telescope at La Silla, Chile between October 1, 2004 and March 31, 2005. Abundance

In this project spectra of neutral calcium between 2000-30000 cm-1 have been recorded by the Fourier Transform Spectrometer Bruker HR IRFTS at Lund Observatory. Using 204 spectral lines, 78 energy levels in the calcium atom have been derived. Level mixing and self absorption of some transitions are discussed. The energy levels in the previously not resolved triplet 4s5g 3G have been measured in th

Gravitational light deflection in the Solar System can be detected by high precision astrometric measurements. We discuss the parametrized post-Newtonian framework and the comparison of metric theories of gravity. At the precision of a few micro-arcseconds, Gaia data will permit tests of the PPN parameters beta and gamma and to distinguish monopole and quadrupole gravitational light deflection. Ac