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Dissertations / Theses on the topic 'Astronomy Stars'

Author: Grafiati

Published: 4 June 2021

Last updated: 1 February 2022

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1

Rosen, Anna L. "The Destructive Birth of Massive Stars & Massive Star Clusters." Thesis, University of California, Santa Cruz, 2017. http://pqdtopen.proquest.com/#viewpdf?dispub=10274404.

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<p> The injection of energy and momentum into the interstellar medium by young massive stars’ intense radiation fields and their fast, radiatively driven winds can have a profound influence on their formation and environment. Massive star forming regions are rare and highly obscured, making the early moments of their formation difficult to observe. Instead, we must turn to theory to elucidate the physics involved in the formation of massive stars and massive star clusters (MSCs), which can host thousands of massive stars. In my thesis, I developed analytical and numerical techniques to s

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2

Glenn, Jason 1968. "Millimeter-wave polarimetry of star formation regions and evolved stars." Diss., The University of Arizona, 1997. http://hdl.handle.net/10150/282440.

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A new λ = 1.3 mm polarimeter, Cyclops, was constructed to make observations of dust continuum emission from star formation regions. The polarization of the inner arcminute of DR 21 was mapped with Cyclops. The polarization percentage and position angle are remarkably constant, indicating a uniform magnetic field throughout the cloud. Turbulent gas motions are a more significant source of support against self gravity in the cloud core than thermal pressure or magnetic fields. The polarization toward the cloud core increases slightly from λ = 100 μm to λ = 2 mm and is consistent with the standar

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3

Herard, Thomas. "The magnetic fields of exoplanet hostM-dwarf stars : The magnetic fields of exoplanet hostM-dwarf stars." Thesis, Uppsala universitet, Teoretisk astrofysik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-455262.

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The majority of stars in the Milky Way are M dwarfs whichmake up 75 % of stars in the vicinity of the sun. As the magneticfield of stars can significantly affect the interiors and theatmospheres of the exoplanets they host within the stellar system,characterising this magnetic field is of major importance.In this work, we selected a sample of 23 exoplanet hostM dwarfs and analysed the observations made by the highresolutionspectropolarimeters ESPaDOnS and NARVAL availablein PolarBase for these stars. In particular, we used theLSD Stokes I and V spectra to measure the projection alongthe line o

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4

Siderud, Emelie. "Dust emission modelling of AGB stars." Thesis, Uppsala universitet, Observationell astrofysik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-423949.

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5

Nordlander, Thomas. "Atomic Diffusion in Old Stars : Testing parameter degeneracies." Thesis, Uppsala universitet, Institutionen för fysik och astronomi, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-158223.

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The predicted primordial lithium abundance differs from observations of unevolved halo stars on the Spite plateau by a factor two to three. Surface depletion due to atomic diffusion has been suggested as a cause of this so-called cosmological lithium problem. Evolutionary abundance trends indicative of atomic diffusion have previously been identified in the metal-poor globular cluster NGC 6397 ([Fe/H] = -2), with stellar parameters deduced spectroscopically in a self-consistent manner. Abundances of five elements (Li, Mg, Ca, Ti, and Fe) were found to be in agreement with stellar structure mod

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6

Harrop-Allin, Margaret. "Superhumps in AM Canum Venaticorum stars." Master's thesis, University of Cape Town, 1996. http://hdl.handle.net/11427/19686.

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Bibliography: pages 205-214.<br>The AM Canum Venaticorum stars are an in homogeneous group of six stars that are characterised by the absence of hydrogen lines in their spectra. The structure of these stars has been the subject of much debate, and single star models were considered as recently as 1992. The prevailing opinion, however, is that the A.Jf eVn stars are semi-detached binaries which consist of a low-mass, degenerate helium secondary which is transferring mass via an accretion disc to a DB white dwarf. Under this model, the orbital periods of the AM CVn systems are in the range 1000

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7

Pretorius, Magaretha L. "Rapid oscillations in cataclysmic variable stars." Master's thesis, University of Cape Town, 2004. http://hdl.handle.net/11427/6103.

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Includes bibliographical references (p. 129-146).<br>Rapid quasi-coherent oscillations were detected in the optical light curves of 24 cataclysmic variable stars (CVS). In 12 of these systems (TU Men, WW Cet, HX Peg, BP CrA, BR Lup, HP Nor, AG Hya, TW Vir, PU CMa, V426 Ooph, V1193 Ori, and CR Boo) for the first time. The results contribute to the observational record of the phenomenology of dwarf nova oscillations (DNOs), quasi-periodic oscillations (QPOs), and longer period dwarf nova oscillations (lpDNOs), strengthen the correlation, valid over nearly six orders of magnitude in frequency, be

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8

Romero, Daniela. "Comparing the Period-Luminosityrelationships in variable stars." Thesis, Uppsala universitet, Institutionen för fysik och astronomi, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-323634.

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There are four Period Luminosity relations from three sources, [3, 5, 9, 11], that are compared for theiraccuracy in calculating distances and to see how much uncertainty has to be considered when calculatingother distances based on these. Here, the relations are compared by using each to calculate and compare thedistances of the stars: BK Vir, L2 Pup, R Hor, R Hya, R Lep, and RR Aql; along with using data from AAVSOand SIMBAD in the calculations. The relations have an uncertainty that ranges from about 30%-40%, exceptfor the relation from [9] that has an uncertainty of 90%

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9

De, Rosa Robert John. "The volume-limited A-star survey : exploring the multiplicity of intermediate mass stars." Thesis, University of Exeter, 2012. http://hdl.handle.net/10036/3544.

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I present the results of the first volume-limited adaptive optics multiplicity survey of A-type stars. Using high-resolution observations obtained using adaptive optics instruments at five observatories, I have estimated the frequency of binary companions to a sample of 233 A-type stars within 60 parsecs. The survey is complete within a projected separation range of $56 < a{\rm [AU]} \le 891$, and a companion mass ratio range of $0.05 \le q \le 1.00$, corresponding to the bottom of the Main Sequence for companions to A-type stars. The multiplicity fraction of the sample, when corrected for

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10

Martin, Alexander John. "Spectropolarimetric analysis of magnetic stars." Thesis, Keele University, 2017. http://eprints.keele.ac.uk/3030/.

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The spectra of Ap and Bp stars show evidence of non-homogenous distributions of chemical elements both vertically and horizontally, along with the presence of largescale ordered magnetic fields. The atomic diffusion theory in stellar atmospheres explains the presence of the non-homogenous element distributions as a result of the magnetic field’s effect on the radiative pressure in the photosphere. Recent modelling of the abundance distributions in Ap and Bp stars has questioned the results determined theoretically. In addition, there has been a debate over the uniqueness and reliability of the

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11

Medupe, Rodney. "Atmospheric temperature structure in the RoAp stars." Master's thesis, University of Cape Town, 1996. http://hdl.handle.net/11427/18483.

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The rapidly oscillating Ap (roAp) stars are a sub-group of the chemically peculiar stars of class 2 (CP2), which are characterised by peculiar spectra and anomalously strong lines of Sr, Cr, Eu and other rare earth elements. They have strong global dipole magnetic fields with effective strengths of up to a few thousand gausses. Stars showing these phenomena cover the spectral range B8p to F0 V-IV. About 20 years ago rapid non-radial pulsations were discovered in the coolest members of the CP2 group, namely the roAp stars. These pulsations are due to high over-tone, low degree p modes with peri

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12

Totten, Edward James. "Carbon stars in the Galactic Halo." Thesis, Queen's University Belfast, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.263490.

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13

Shenton, Mervyn. "Multiwavelength study of RV Tauri stars." Thesis, Keele University, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.304453.

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14

Hutcheon, Richard J. "Fundamental properties of solar-type eclipsing binary stars, and kinematic biases of exoplanet host stars." Thesis, Keele University, 2015. http://eprints.keele.ac.uk/1202/.

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This thesis is in three parts: 1) a kinematical study of exoplanet host stars, 2) a study of the detached eclipsing binary V1094 Tau and 3) and observations of other eclipsing binaries. Part I investigates kinematical biases between two methods of detecting exoplanets; the ground based transit and radial velocity methods. Distances of the host stars from each method lie in almost non-overlapping groups. Samples of host stars from each group are selected. They are compared by means of matching comparison samples of stars not known to have exoplanets. The detection methods are found to introduce

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15

Boyajian, Tabetha Suzanne. "Sizing Up the Stars." Digital Archive @ GSU, 2009. http://digitalarchive.gsu.edu/phy_astr_diss/34.

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For the main part of this dissertation, I have executed a survey of nearby, main sequence A, F, and G-type stars with the CHARA Array, successfully measuring the angular diameters of forty-four stars to better than 4% accuracy. The results of these observations also yield empirical determinations of stellar linear radii and effective temperatures for the stars observed. In addition, these CHARA-determined temperatures, radii, and luminosities are fit to Yonsei-Yale isochrones to constrain the masses and ages of the stars. These quantities are compared to the results found in Allende Prieto & L

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16

Norgren, Ofelia. "Pulsation Properties in Asymptotic Giant Branch Stars." Thesis, Uppsala universitet, Teoretisk astrofysik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-388388.

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Asymptotic Giant Branch (AGB) stars are stars with low- to intermediate mass in a late stage in their stellar evolution. An important feature of stellar evolution is the ongoing nucleosynthesis, the creation of heavier elements. Unlike main sequence stars, the AGB stars have a thick convective envelope which makes it possible to dredge-up the heavier fused elements from the stellar core to its surface. AGB stars are also pulsating variable stars, meaning the interior expands and contracts, causing the brightness to fluctuate. These pulsations will also play a major role in the mass loss observ

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17

Doyle, Amanda. "Spectral analyses of solar-like stars." Thesis, Keele University, 2015. http://eprints.keele.ac.uk/767/.

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Accurate stellar parameters are important not just to understand the stars themselves, but also for understanding the planets that orbit them. Despite the availability of high quality spectra, there are still many uncertainties in stellar spectroscopy. In this thesis, the finer details of spectroscopic analyses are discussed and critically evaluated, with a focus on improving the stellar parameters. Using high resolution, high signal-to-noise HARPS spectra, accurate parameters were determined for 22 WASP stars. It is shown that there is a limit to the accuracy of stellar parameters that can be

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18

Townsend, Richard Henry Denny. "Non-radial pulsation of early-type stars." Thesis, University College London (University of London), 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.265968.

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19

Ivison, Robert Julian. "A multi-frequency study of symbiotic stars." Thesis, University of Central Lancashire, 1992. http://clok.uclan.ac.uk/20822/.

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Multi-frequency observations using a wide variety of telescopes and instrumentation have been used to throw light upon some of the physical characteristics of symbiotic stars. A detailed understanding of these enigmatic binaries requires the planning of large, simultaneous observing campaigns to obtain the maximum possible range of diagnostic tools - line ratios, profiles and intensities and continuum flux densities. This then is the general theme of the work presented in this thesis. The results of a low dispersion, optical spectroscopic survey of northern sky symbiotics are presented and ref

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20

Baskill, Darren Stuart. "X-ray properties of cataclysmic variable stars." Thesis, University of Leicester, 2003. http://hdl.handle.net/2381/30669.

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In this thesis, I study the entire sample of non-magnetic cataclysmic variables observed with the Japanese satellite ASCA, presenting a detailed analysis of the spectral and temporal behaviour of these twenty-nine targets. The spectral analysis indicates that all the targets in the ASCA sample appear to be X-ray under-luminous, with only three possible exceptions. This indicates that energy is being lost from the accretion disk in a non-radiative way. Since a third of the observations require additional absorption above that expected from interstellar alone, both the X-ray under-luminosity and

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21

Bengtz, Oskar. "Chemical signatures of the first stars." Thesis, Uppsala universitet, Institutionen för fysik och astronomi, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-326091.

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The first stars are something many scientists are curious about. How did they formand how did the universe look like at that time? These stars however probably died along time ago, or are at a distance too far away from us to be observable. If these starsexploded and formed supernovae there might be stars observable today that formed fromthe ejecta of these supernovae. Models of nucleosynthesis in the first stars may potentiallybe used to infer parameters of progenitor supernovae from chemical abundances in old,metal-poor stars. This thesis aim is to find out how precise these abundances need

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22

Stempels, Henricus Cornelis. "An Observational Study of Accretion Processes in T Tauri Stars." Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis : Univ.-bibl. [distributör], 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-3420.

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23

Staley, Timothy. "Lucky imaging : beyond binary stars." Thesis, University of Cambridge, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.607953.

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24

Zbinden, Jonas. "Planning Observations of Terrestrial ExoplanetsAround M Type Stars with CRIRES+." Thesis, Uppsala universitet, Observationell astrofysik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-437673.

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In recent decades, thousands of exoplanets have been discovered. The next step is to characterize theobserved planets in terms of their radii, masses, density, physical conditions and composition of theiratmospheres. Several space-based observatories such as TESS and CHEOPS have started determiningthe first three observables but characterization of exoplanetary atmospheres is waiting for observationcampaigns with instruments like CRIRES+ at the VLT and NIRSpec on the JWST. To ensure the efficiencyof data acquisition, careful planning of observations is necessary. In this project we developeda

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Shrestha, Joseph, Jennifer L. Hoffman, Richard Ignace, and Hilding R. Neilson. "Astronomy in Denver: Polarization of Bow Shock Nebulae around Massive Stars." Digital Commons @ East Tennessee State University, 2018. https://dc.etsu.edu/etsu-works/5507.

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Stellar wind bow shocks are structures created when stellar winds with supersonic relative velocities interact with the local interstellar medium (ISM). They can be studied to understand the properties of stars as well as the ISM. Since bow shocks are asymmetric, light becomes polarized by scattering in the regions of enhanced density they create. We use a Monte Carlo radiative transfer code calle SLIP to simulate the polarization signatures produced by both resolved and unresolved bow shocks with analytically derived shapes and density structures. When electron scattering is the polarizing me

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Votruba, V., Achim Feldmeier, J. Kubát, and D. Rätzel. "Multicomponent stellar wind of hot stars." Universität Potsdam, 2007. http://opus.kobv.de/ubp/volltexte/2008/1767/.

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27

Czekala, Ian. "The Fundamental Properties of Young Stars." Thesis, Harvard University, 2016. http://nrs.harvard.edu/urn-3:HUL.InstRepos:33493279.

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Accurate knowledge of the fundamental properties of stars--mass, temperature, and luminosity--is key to our understanding of stellar evolution. In particular, empirical measurements of stellar mass are difficult to make and are generally limited to stars that dynamically interact with a companion (e.g., eclipsing or astrometric binaries), a precious but ultimately small sample. We developed a technique that uses the rotation of the protoplanetary disk--a consequence of the star formation process still present around many pre-main sequence stars--to measure the stellar mass. To establish the ab

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Gerke, Jill R. "Failed Supernovae, Dusty Stars and Cepheid Distances." The Ohio State University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=osu1405528289.

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29

Davies, John Keith. "Photometric monitoring of early type emission line stars." Thesis, University of Central Lancashire, 1988. http://clok.uclan.ac.uk/20181/.

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A programme of simultaneous optical (UBVRI) and infrared (JHKL MNQ) photometry of early type, emission line, stars is described. Particular emphasis is placed on observations of suspected pre-main-sequence objects such as Herbig Ae/Be stars. The observations, together with data from the IRAS point source catalogue, are analysed to probe the circumstellar environments of these objects and to determine the extent and causes of optical variability in such stars. It was found that many of these stars are associated with warm circumstellar dust and that the mean temperature of that dust is higher t

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Hickman, Richard D. G. "Multi-wavelength observations of cataclysmic variable stars." Thesis, University of Warwick, 2011. http://wrap.warwick.ac.uk/38153/.

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Observations of the cataclysmic variable systems EX Dra, Z Cha, and OY Car using multi-wavelength data ranging from near-infrared to X-ray bands are presented and analysed. Obscuration of the white dwarf by intervening material is discussed in context of all three systems, including the confirmation of iron lines in the spectrum of OY Car and the absorbing nature of the accretion disc upon the soft X-ray band in Z Cha. Evidence for spiral shocks and slingshot prominences from the secondary star are found in EX Dra, while the extent of Z Cha's boundary layer is probed with extensive modelling o

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31

Jonsell, Karin. "Chemical Abundance Analysis of Population II Stars : The Summary Includes a Background in General Astronomy." Doctoral thesis, Uppsala University, Department of Astronomy and Space Physics, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-6034.

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<p>We are made of stardust in the sense that most atomic nuclei around us have been formed by stars. Stars synthesise new elements and expel them to the interstellar medium, from which later new generations of stars are born. We can map this chemical evolution by analysing the atmospheric contents of old Galactic halo stars. I have done two such investigations. A vigourous debate is going on whether the oxygen-to-iron ratio varies strongly with the general metal-content of halo stars. In my first study, I made an abundance analysis of 43 halo stars, and found no support for such a variation. I

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Prieto, Jose L. "Massive Stars: Life and Death." The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1248987393.

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33

Schmidt, Luca. "Formation of Eu II spectral features in magnetic chemically peculiar stars." Thesis, Uppsala universitet, Institutionen för fysik och astronomi, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-418059.

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The advancing resolution of modern spectrometers uncovers increasingly detailed spectral features in astrophysical observations which can be attributed to properties of the energy structure of the corresponding atomic systems such as fine, hyperfine and Zeeman splitting. At the same time, increasing computational power enables us to include these quantum mechanical interactions on different levels of sophistication in our theoretical atomic structure calculations. This project aims at investigating the hyperfine and Zeeman splitting in five spectral lines of singly-ionized Europium which are r

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34

Husseini, Majid. "Magnetic field strength of chemically peculiar A and B-type stars." Thesis, Uppsala universitet, Institutet för rymdfysik, Uppsalaavdelningen, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-454565.

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The goal of this work is to detect Zeeman split lines and measure magnetic field strength in a sample of Ap stars. This work aims to analyse spectra of 454 stars and find stars that show spectral lines resolved into their magnetically split components. The work included writing and applying a computer code to visualize astronomical spectra and estimate the mean surface magnetic field strength by fitting resolved Zeeman split lines. The data represent spectroscopic measurements obtained from November 2018 to March 2020 with the HERMES spectrograph. This study investigated high-resolution spectr

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Hogg, Michael. "Neutron stars and their terrestrial analogues." Thesis, University of Southampton, 2014. https://eprints.soton.ac.uk/366019/.

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When we consider in detail the behaviour of a fluid consisting of two (or possibly more) interpenetrating components, the likelihood of dynamical instabilities induced by coupling between the two fluids cannot be ignored. The phenomenon is generic to all such multi fluid systems and as such is appellated the two-stream instability. Mathematically this class of instability is somewhat akin to the more well known Kelvin Helmholtz instability, but is distinguished by the fluids flowing through each other rather than having a clearly defined interface between them. In this thesis we describe in so

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Hultquist, Adam. "Stellar atmosphere models for Population III stars." Thesis, Uppsala universitet, Observationell astrofysik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-432178.

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The rst stars to illuminate the universe are said to belong to a group called Population III. Having knowledge of their atmospheric conditions would be useful in many endeavours. The aimof this project was to compile and run the FORTRAN code TLUSTY (Hubeny and Lanz 2017) inorder to create stellar atmospheres for Pop III stars. With a working version of TLUSTY, severalcontrol runs were then performed to make sure that everything worked as intended with the final goal to create a large grid of calculated atmospheres in the parameter space of effective temperatureand surface gravity. Successful

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Sandin, Christer. "A Study of Grain Drift in C Stars : Theoretical Modeling of Dust-Driven Winds in Carbon-Rich Pulsating Giant Stars." Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis : Univ.-bibl. [distributör], 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-3397.

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Petigura, Erik Ardeshir. "Prevalence of Earth-size Planets Orbiting Sun-like Stars." Thesis, University of California, Berkeley, 2015. http://pqdtopen.proquest.com/#viewpdf?dispub=3720767.

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<p> In this thesis, I explore two topics in exoplanet science. The first is the prevalence of Earth-size planets in the Milky Way Galaxy. To determine the occurrence of planets having different sizes, orbital periods, and other properties, I conducted a survey of extrasolar planets using data collected by NASA’s <i>Kepler Space Telescope</i>. This project involved writing new algorithms to analyze <i>Kepler</i> data, finding planets, and conducting follow-up work using ground-based telescopes. I found that most stars have at least one planet at or within Earth’s orbit and that 26%

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De, Marco Orsola. "Cool Wolf-Rayet central stars and their planetary nebulae." Thesis, University College London (University of London), 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.267831.

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Stroud, Matthew Paul. "The origin of ejecta nebulae surrounding evolved massive stars." Thesis, University College London (University of London), 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.300450.

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Davies, B., J. S. Vink, and R. D. Oudmaijer. "Modelling the polarimetric variability of hot stars." Universität Potsdam, 2007. http://opus.kobv.de/ubp/volltexte/2008/1793/.

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Many hot stars exhibit stochastic polarimetric variability, thought to arise from clumping low in the wind. Here we investigate the wind properties required to reproduce this variability using analytic models, with particular emphasis on Luminous Blue Variables. We find that the winds must be highly structured, consisting of a large number of optically-thin clumps; while we find that the overall level of polarization should scale with mass-loss rate – consistent with observations of LBVs. The models also predict variability on very short timescales, which is supported by the results of a recen

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Gonzalez, Marjorie. "X-ray observations of young neutron stars." Thesis, McGill University, 2008. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=18813.

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The extreme physical properties of neutron stars make them efficient emitters at all wavelengths of the electromagnetic spectrum and, traditionally, they have been extensively studied at radio wavelengths. The neutron stars with the highest estimated magnetic fields (so-called "magnetars") have remarkably different characteristics from the rest of the population: they emit no persistent radio emission but show large amounts of high-energy radiation that is thought to be powered by their large magnetic fields. For this thesis we have studied the X-ray emission properties of various types of you

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Carter, Philip J. "Estimating the space density of ultracompact binary stars." Thesis, University of Warwick, 2014. http://wrap.warwick.ac.uk/63942/.

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The AM Canum Venaticorum (AM CVn) binaries are a rare group of hydrogen-deficient, ultrashort period, mass-transferring white dwarf binaries, some of which may be Type Ia supernova progenitors. These systems represent the end product of several finely-tuned evolutionary pathways, and as such are of great interest for binary stellar evolution theory. They are also some of the strongest known sources of low-frequency gravitational waves. Establishing their space density is important for constraining evolutionary models, and the signals we expect to detect from the Galactic population. This has b

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Tarrant, Neil James. "Asteroseismology from the main sequence to giant stars." Thesis, University of Birmingham, 2010. http://etheses.bham.ac.uk//id/eprint/736/.

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The thesis focuses on the use of asteroseismology to probe the structure of stellar sources. By observing pulsational variability, a detailed description of the interior of stars, and the determination of stellar parameters can be obtained. An extensive sample of bright K and M class giant stars were surveyed to detect the presence of any noticeable variability. Three giant stars have been studied in detail. In Arcturus (alpha Boo), no oscillations at a significant amplitude were detected. In beta UMi (Kochab) multiperiodic oscillations have been observed for the first time, allowing an astero

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Asbell, Jessica Lee. "Non-radial fluid pulsation modes of compact stars." Thesis, California State University, Long Beach, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10150591.

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<p> The observation of gravitational waves from compact stars (neutron and quark stars) is a promising method of determining their internal composition. This research presents the details and results for calculations of some of the principal modes of compact star oscillations, by which they radiate gravitational waves. These are: the <i>f</i>-modes, <i>p</i>-modes, and <i>g</i>-modes. We find that for the same stellar mass, the <i> f</i>-modes for quark stars are higher in frequency than for neutron stars. The <i>p</i>-mode frequency of quark stars decrease with stellar mass, displaying an

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Hall, II Zack B. "General Relativistic Non-Radial Oscillations in Compact Stars." Thesis, California State University, Long Beach, 2017. http://pqdtopen.proquest.com/#viewpdf?dispub=10604673.

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<p> Currently, we lack a means of identifying the type of matter at the core of compact stars, but in the future, we may be able to use gravitational wave signals produced by fluid oscillations inside compact stars to discover new phases of dense matter. To this end, we study the fluid perturbations inside compact stars such as Neutron Stars (NS) and Strange Quark Stars (SQS), focusing on modes that couple to gravitational waves (GWs). Using a modern equation of state for quark matter that incorporates interactions at moderately high densities, we implement an efficient computational scheme to

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Persson, Magnus. "T Tauri stars : Optical lucky imaging polarimetry of HL and XZ Tau." Thesis, Stockholm University, Department of Astronomy, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-35802.

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<p>Optical lucky imaging polarimetry of HL Tau and XZ Tau in the Taurus-Auriga molecular cloud was carried out with the instrument PolCor at the Nordic Optical Telescope (NOT). The results show that in both the V- and R-band HL Tau show centrosymmetric structures of the polarization angle in its northeastern outflow lobe (degree of polarization ~30%). A C-shaped structure is detected which is also present at near-IR wavelengths (Murakawa, 2008), and higher resolution optical images (Stapelfeldt, 1995). The position angle of the outflow is 47.5+-7.5 degrees, which coincides with previous measur

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Peter, Camaren. "The red clump stars as a distance indicator : review and application." Master's thesis, University of Cape Town, 2002. http://hdl.handle.net/11427/7411.

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Bibliography: leaves 76-81.<br>The intention of this project was primarily to determine the distance to the Galactic Centre using a new technique pioneered by Paczynski and Stanek (1998) that uses the red clump stars as a standard candle. This was made possible by the large number of stars simultaneously observed by the OGLE microlensing project which yields well-deﬁned red clump structures in their colour magnitude diagrams. We have used data obtained at Sutherland in July 1997, in collaboration with the PLANET microlensing project. It was hoped that the observation of a number of lensing ev

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Olsson, Emma. "Many-body Problems in the Theory of Stellar Collapse and Neutron Stars." Doctoral thesis, Uppsala University, The Uppsala Astronomical Observatory, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-4704.

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<p>When modelling the collapse of massive stars leading to supernova explosions and the cooling of neutron stars, understanding the microphysical processes, such as the interaction of neutrinos within a dense medium are of vital importance. The interaction of neutrinos with nucleons (neutrons and protons) is altered by the presence of the medium, compared to the same process with free nucleons. Neutrino scattering and production processes may be characterized in terms of the excitations that are created or destroyed in the nuclear medium. One way to analyse the effects of the medium is by usin

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Johnston, Katharine G. "Observational signatures of massive star formation : an investigation of the environments in which they form, and the applicability of the paradigm of low-mass star formation." Thesis, University of St Andrews, 2011. http://hdl.handle.net/10023/1895.

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This thesis presents both a study of the cluster-scale environments in which massive stars form, investigating in particular how the ionized gas in these regions relates to the molecular star-forming material, as well as detailed studies of two luminous forming stars, AFGL 2591 and IRAS 20126+4104, to determine whether they are forming similarly to their low-mass counterparts. The results of this work include the identification of 35 HII regions (20 newly discovered) via a radio continuum survey of ionized gas towards 31 molecular cluster-forming clumps. The observed ionized gas was found to b

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