Sökresultat

Stellar abundances are important for understanding the chemical evolution of galaxies and provide us with constraints on stellar evolution and supernova nucleosynthesis. To determine stellar abundances accurately, atomic data is crucial. This data is incomplete for many elements, especially in the infrared region. In particular, hyperfine structure (hfs) data in the near-infrared region is lacking

A selection of well known period luminosity relations for cepheid variables are studied under the assumption that cepheid variables have a mean vertical velocity of zero in the galactic plane. Proper motion data from Hipparcos and Thyco-2 catalogues are coupled with the distances obtained from applying the period luminosity relations on a database of known classical cepheids to calculate the veloc

In this project I have studied the effect of gas expulsion on the evolution of stellar clusters. What effect the rate of gas removal and the quantity of gas removed has on the evolution on the cluster will be studied through computer simulations with the NBody6 code and compared to analytical predictions. The rate at which gas is removed has a very significant impact on how the cluster evolves

In this report we present the testing and development made using the Lund Observatory Vacuum Echelle Spectrograph (LOVES) during the last few years. Hardware development includes an assembly from base components due to relocation and necessary calibrations of the optics. Software devel- opment includes the making of a basic image processing pipeline for the instrument. The testing of LOVES wavelen

Over the past two decades many discoveries of exoplanets have been made, which have drawn much attention to extrasolar planetary systems. In this work we study the composition of these systems and search for analogues of the Solar System. We considered the planets in the database at exoplanet.eu. The search of solar-like systems required these planets to be classified. The classification was perf

Star clusters can harbour many exotic objects, including black holes (BHs), X-ray binaries and blue straggler stars. In dense stellar environments like globular clusters (GCs), two-body relaxation drives their dynamical evolution, where gravitational interactions between stars strive to equalize their kinetic energy in the cluster. Theoretical studies have indicated that some of these clusters can

Context. The discovery of hot Jupiters, giant gas exoplanets on tight orbits close to their host star, has proven instrumental in the study of exoplanet atmospheres through transit spectroscopy. Just as a temperature increase with height manifests in Earth’s atmosphere due to ozone absorbing ultraviolet radiation, transit spectra of some hot Jupiters has yielded evidence that suggests the presence

Context. With the goal to accurately map about a billion of the Milky Way stars, the astrometric satellite Gaia was launched in December 2013. Its high precision and sensitivity will lead to better understanding of the Galactic structure and evolution. Also, it will be possible to probe the matter distribution in the Galaxy. Aims. To study how well the Galactic matter distribution can be determin

Context. Intensity interferometry was invented and used by R.Hanbury Brown and R.Q.Twiss in the 1960's to measure stellar angular diameters. Its main advantage over conventional interferometry is that it enables very long baselines and is insensitive to poor seeing. However, because it requires very large light collectors, it was never pursued further. The Cherenkov Telescope Array (CTA) is a

In this thesis, I present a case where Dark Matter subhalos would annihilate at some stage in their lifetime. The implication of this scenario could potentially aid the Missing Satellites and the Cusp-Core density profile problem. The Dark Matter particles’ annihilation process and effective “friction” lead to an energy and momentum loss into radiation and hence to the destabilization of the Dark

Context: Data from the recently launched astrometric satellite Gaia will be coming in soon with the final data release expected in 2022. This will provide a very precise map of the Galaxy. The Solar system and Galaxy is thought to be filled with invisible bodies (planetesimals, planets, brown dwarfs, neutron stars, black holes, etc.) and they will affect the observations via gravitational lensing.

The origin of the class of exoplanets typically referred to as hot Jupiters is to this day an unsettled matter. Some of the proposed formation channels predict certain values of the spin-orbit misalignment parameter, i.e. the angle between the stellar rotation axis, and the angular momentum vector of the planet orbit. One such formation channel is tidal capture following Kozai resonance (TCKR). Th

Most of the things that we know about stars come from their spectrum. The properties of the atomic lines, e.g. energy levels, wavelengths, oscillator strengths, must be known to understand the observed spectrum and to perform quantitative analyses. Atomic data of some elements are incomplete, especially in the near-infrared region, which makes it difficult or even impossible to analyze a stellar s

We investigate the radial infall of ice pebbles in a protoplanetary disk, and how these tend to end up in relatively close proximity to eachother, providing a possible spawning ground for planets. These pebbles have dust particles embedded in them, which are released as the pebble crosses the so-called ice- line, where the ice evaporates. This is interesting as the dust will pile up around this ic