Browsing Institutt for teoretisk astrofysikk by Title
Now showing items 117-136 of 1279
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(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2019)
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(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2020)We examine the capabilities of a fast and simple method to infer line-of-sight (LOS) velocities from observations of the photospheric Si I 10 827 Å line. This spectral line is routinely observed together with the chromospheric ...
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(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2020)Context. Hot coronal jets are a basic observed feature of the solar atmosphere whose physical origin is still actively debated. Aims. We study six recurrent jets that occurred in active region NOAA 12644 on April 4, 2017. ...
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(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2016)Context. The He i 1083 nm is a powerful diagnostic for inferring properties of the upper solar chromosphere, in particular for the magnetic field. The basic formation of the line in one-dimensional models is well understood, ...
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(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2023)Context. Observations of center-to-limb variations (CLVs) of spectral lines and continua provide a good test for the accuracy of models with a solar and stellar atmospheric structure and spectral line formation. They are ...
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(Master thesis / Masteroppgave, 2009)En mulig forklaring på at universet gikk inn i en fase av akselerert ekspansjon for 5-6 milliarder år siden, er at energitettheten i universet inneholder et bidrag fra et dynamisk skalarfelt. Problemet med denne forklaringen ...
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(Master thesis / Masteroppgave, 2010)We investigate scalar-field theories with a field-dependent coupling to matter and show the existence of a chameleon mechanism. The thin-shell solutions for a spherical body are found, and used to investigate the consequences ...
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(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2015)We present Chandra and XMM-Newton observations of PLCK G036.7+14.9 from the Chandra–Planck Legacy Program. The high resolution X-ray observations reveal two close (~72'' = 193 kpc in projection) subclusters, G036N and ...
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(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2017)We present the results of work involving a statistically complete sample of 34 galaxy clusters, in the redshift range 0.15 ≤ z ≤ 0.3 observed with Chandra. We investigate the luminosity–mass (LM) relation for the cluster ...
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(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2021)Context. Metrewave solar type-III radio bursts offer a unique means to study the properties of turbulence across coronal heights. Theoretical models have shown that the apparent intensity and size of the burst sources ...
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(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2023)Abstract To recognize gravitational wave lensing events and being able to differentiate between similar lens models will be of crucial importance once one will be observing several lensing events of gravitational waves per ...
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(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2023)ABSTRACT We introduce a novel unbiased, cross-correlation estimator for the one-point statistics of cosmological random fields. One-point statistics are a useful tool for analysis of highly non-Gaussian density ...
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(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2019)We characterize, for the first time, type-II spicules in Ca II K 3934 Å using the CHROMIS instrument at the Swedish 1 m Solar Telescope. We find that their line formation is dominated by opacity shifts with the K3 minimum ...
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(Journal article / Tidsskriftartikkel / AcceptedVersion; Peer reviewed, 2020)Observations at millimetre wavelengths provide a valuable tool to study the small-scale dynamics in the solar chromosphere. We evaluate the physical conditions of the atmosphere in the presence of a propagating shock wave ...
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Characterizing the intracluster light over the redshift range 0.2 < z < 0.8 in the DES-ACT overlap (Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2023)ABSTRACT We characterize the properties and evolution of bright central galaxies (BCGs) and the surrounding intracluster light (ICL) in galaxy clusters identified in the Dark Energy Survey and Atacama Cosmology ...
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(Master thesis / Masteroppgave, 2022)The Interface Region Imaging Spectrograph (IRIS) provides simultaneous imaging and spectral data of the chromosphere and transition region (TR) with great spatial, spectral and temporal resolution. A Solar coronal hole ...
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Charged Black Hole Mergers: Emissions, Orbital Evolution, Gravitational Waveform and Observer Bias (Master thesis / Masteroppgave, 2020)Gravitational waveforms from mergers or close-encounters of astrophysical compact bodies provide a new and separate window into high energy physics and dark objects. Although there is a zoo of theoretical compact objects ...
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(Journal article / Tidsskriftartikkel / AcceptedVersion; Peer reviewed, 2021)We consider the inspiral of black holes carrying U(1) charge that is not electromagnetic, but corresponds to some dark sector. In the weak-field, low-velocity regime, the components follow Keplerian orbits. We investigate ...
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(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2023)Abstract We present a detailed chemical abundance analysis of the brightest star in the ultrafaint dwarf (UFD) galaxy candidate Cetus II from high-resolution Magellan/MIKE spectra. For this star, DES J011740.53-173053, ...
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(Journal article / Tidsskriftartikkel / PublishedVersion; Peer reviewed, 2020)