Sökning: "astrophysics"

Visar resultat 26 - 30 av 58 uppsatser innehållade ordet astrophysics.

  1. 26. Accurate Abundances of Giant Stars in the Local disk: A manual analysis of IR APOGEE spectra

    Master-uppsats, Lunds universitet/Astronomi - Genomgår omorganisation; Lunds universitet/Institutionen för astronomi och teoretisk fysik - Genomgår omorganisation

    Författare :Ivalu Barlach Christensen; [2020]
    Nyckelord :Galactic Chemical Evolution; Astrophysics; Astronomy; IR Spectroscopy; Milky Way; Abundance; Physics and Astronomy;

    Sammanfattning : Purpose: In order to study the Galactic Chemical Evolution, elemental abundances are needed. The purpose of this work is to investigate the chemical evolution of the Milky Way by determining several elemental abundances of giants in the local disk. LÄS MER

  3. 27. Efficient Discovery Of Binary Stars

    Master-uppsats, Lunds universitet/Astronomi - Genomgår omorganisation; Lunds universitet/Institutionen för astronomi och teoretisk fysik - Genomgår omorganisation

    Författare :Pablo Navarro Barrachina; [2020]
    Nyckelord :Binary Stars; Spectroscopic binary stars; SB2; Machine Learning; Data Mining; Physics and Astronomy;

    Sammanfattning : Purpose: even in the era of exponential increase in the amount of stellar data gathered, binaries are still often overlooked in observational data due to the special handling they require. The goal of this work is to develop a method capable of automatically and efficiently identifying and extract double-lined spectroscopic binaries (SB2) from a spectroscopic survey, while being scalable and technically successful, and to identify and optimize the parameters that influence their detection. LÄS MER

  4. 28. How Odd is Betelgeuse?

    Kandidat-uppsats, Lunds universitet/Astronomi - Genomgår omorganisation

    Författare :Martin Oshaughnessy; [2020]
    Nyckelord :Betelgeuse; runaway stars; stellar evolution; binary interactions; Physics and Astronomy;

    Sammanfattning : The role of massive stars (those with masses greater than eight solar masses) in the chemical enrichment of galaxies and renewed star formation forms an important field of fundamental research in modern astrophysics. The complex nature of massive star evolution produces formidable challenges in furthering our understanding of the processes driving massive star evolution. LÄS MER

  5. 29. Collisional broadening by hydrogenfor stellar spectroscopy : extension towards high-lying states

    Kandidat-uppsats, Uppsala universitet/Teoretisk astrofysik

    Författare :Adam Hultquist; [2019]
    Nyckelord :Astrophysics; Spectral line broadening; ABO; Collisional broadening;

    Sammanfattning : The object of this thesis is to extend the current tables for two useful quantities when calculatingcollisional broadening, the cross-section of interaction and the velocity parameter.These quantities, which have hitherto been tabulated for lower states, have now been calculatedfor higher lying states and are used in the ABO - model for spectral line broadening. LÄS MER

  7. 30. An introduction to some ordinary differential equations governing stellar structures

    Kandidat-uppsats, Lunds universitet/Matematik (naturvetenskapliga fakulteten)

    Författare :Yani di Giovanni; [2019]
    Nyckelord :Mathematics and Statistics;

    Sammanfattning : The Lane-Emden equation is a non-linear differential equation governing the equilibrium of polytropic stationary self-gravitating, spherically symmetric star models; $${\frac {1}{\xi ^{2}}}{\frac {d}{d\xi }}\left({\xi ^{2}{\frac {d\theta }{d\xi }}}\right)+\theta ^{n}=0.$$ In the isothermal cases we have the Chandrasekhar equation: $${\frac {1}{\xi ^{2}}}{\frac {d}{d\xi }}\left({\xi ^{2}{\frac {d\psi}{d\xi }}}\right)-e^{-\psi}=0$$ After having derived these models, we will go through all cases for which analytic solutions are achievable. LÄS MER