Sökning: "Astrophysics"

Visar resultat 1 - 5 av 58 uppsatser innehållade ordet Astrophysics.

1. 1. Simulation-based discrimination of Crab pulsar models with XL-Calibur

   Master-uppsats, KTH/Fysik

   Författare :Dennis Åkerström; [2024]
   Nyckelord :Astroparticle Physics; Astrophysics; Detector Physics; Simulation; Theoretical Physics; Engineering Physics; Pulsar models; Crab pulsar; Astropartikelfysik; Astropartikelfysik; Detektorfysik; Simulering; Teoretisk Fysik; Teknisk Fysik; Pulsar modeller; Krabbpulsaren;

   Sammanfattning : Polarisation of X-ray light is being investigated with polarimeters to extend the borders of what can be observed. Distant compact objects, such as pulsars, that are to small on the sky to be analysed with imaging can be investigated by analysing the polarisation of the emitted light. This can reveal physics previously hidden by their small nature. LÄS MER

3. 2. Gravitational Collapse of a Massless Scalar Field in a Theory of Minimally Modified Gravity

   Master-uppsats, KTH/Fysik

   Författare :Atabak Fathe Jalali; [2024]
   Nyckelord :Theoretical physics; astrophysics; modified gravity; minimally modified gravity; gravitational collapse; VCDM; scalar collapse; apparent horizon; numerical relativity; Teoretisk fysik; astrofysik; modifierad gravitation; minimalt modifierad gravitation; gravitationskollaps; VCDM; skalär kollaps; uppenbar horisont; numerisk relativitet;

   Sammanfattning : This thesis explores the spherically symmetric gravitational collapse of a massless scalar field in a minimally modified gravity theory denoted VCDM (V replaces $\Lambda$ in the $\Lambda$CDM abbreviation), a class of theories propagating the same degrees of freedom as general relativity at the expense of broken 4D diffeomorphism invariance. Numerical evolution of the equations of motion reveals that for small initial scalar profile amplitudes, no black hole forms from the collapse. LÄS MER

4. 3. Fitting a photospheric prompt emission model to GRB data: The Kompaneets RMS approximation (KRA)

   Master-uppsats, KTH/Fysik

   Författare :Oscar Wistemar; [2023]
   Nyckelord :Gamma-Ray Bursts; Astrophysics; Engineering Physics; Gamma-Blixtar; Astrofysik; Teknisk Fysik;

   Sammanfattning : Gamma-ray bursts (GRBs) are some of the most energetic events in the universe. Shocks occurring below the photosphere are likely radiation mediated shocks (RMSs) and are suspected to shape the spectra. Due to computational costs of simulating RMSs, models had not been fitted to data and a faster model was needed. LÄS MER

5. 4. A cross-correlation analysis of a warm super-Neptune using transit spectroscopy

   Kandidat-uppsats, Uppsala universitet/Institutionen för fysik och astronomi

   Författare :Elias Önerud; [2023]
   Nyckelord :Cross-correlation; cross-correlation spectroscopy; cross-correlation analysis; super-Neptune; astronomy; astrophysics; WASP-107; WASP-107 b; CRIRES ; SysRem; exoplanet; transmission spectrum; transit;

   Sammanfattning : A study was made in order to deduce whether certain chemical species, namely water (H2O) and carbon monoxide (CO), are present in the atmosphere of the exoplanet WASP-107 b, which lies about 200 light-years away from Earth in the constellation Virgo. The project was carried out at Uppsala University at the Department of Physics and Astronomy. LÄS MER

7. 5. Finding new members of the VelHel-4 stream

   Kandidat-uppsats, KTH/Skolan för teknikvetenskap (SCI)

   Författare :Lucas Johansson; [2023]
   Nyckelord :Galactic Archaeology; Milky Way; Stellar Streams; Streams; Stellar Halo; Stars; Globular Cluster; Astronomy; Astrophysics; Gaia; Chemical Abundance; Spectroscopy;

   Sammanfattning : According to the paradigm of lambda-CDM cosmology, the stellar halo ofour Galaxy has been built-up over time through the accretion of other galaxiesand star clusters. The remnants of some of these are still observable today asstellar streams, but are typically very faint and difficult to resolve amidst the farmore numerous foreground Milky Way stars. LÄS MER