Zobrazeno 1 - 10
of 53
pro vyhledávání: '"Kiselman, Dan"'
Autor:
Kiselman, Dan, Pereira, Tiago, Gustafsson, Bengt, Asplund, Martin, Meléndez, Jorge, Langhans, Kai
Context: In studies of the solar spectrum relative to spectra of solar twin stars, it has been found that the chemical composition of the Sun seems to depart systematically from those of the twins. One possible explanation is that the effect is due t
Externí odkaz:
http://arxiv.org/abs/1108.4527
Publikováno v:
Astronomy & Astrophysics, 533:A82, 2011
Context. Narrow-band interference filters can be tuned toward shorter wavelengths by tilting them from the perpendicular to the optical axis. This can be used as a cheap alternative to real tunable filters, such as Fabry-P\'erot interferometers and L
Externí odkaz:
http://arxiv.org/abs/1108.1234
The measurement of Doppler velocities in spectroscopic solar observations requires a reference for the local frame of rest. The rotational and radial velocities of the Earth and the rotation of the Sun introduce velocity offsets in the observations.
Externí odkaz:
http://arxiv.org/abs/1101.2671
We present results from a series of observational tests to 3D and 1D solar models. In particular, emphasis is given to the line formation of atomic oxygen lines, used to derive the much debated solar oxygen photospheric abundance. Using high-quality
Externí odkaz:
http://arxiv.org/abs/0909.4121
Context: There is a lively debate about the solar oxygen abundance and the role of 3D models in its recent downward revision. The models have been tested using high resolution solar atlases. Further testing can be done using centre-to-limb variations
Externí odkaz:
http://arxiv.org/abs/0909.2310
Aims: we seek to provide additional tests of the line formation of theoretical 3D solar photosphere models. In particular, we set out to test the spatially-resolved line formation at several viewing angles, from the solar disk-centre to the limb and
Externí odkaz:
http://arxiv.org/abs/0909.2307
We present non-Local Thermodynamic Equilibrium (non-LTE) calculations for neutral carbon spectral line formation, carried out for a grid of model atmospheres covering the range of late-type stars. The results of our detailed calculations suggest that
Externí odkaz:
http://arxiv.org/abs/astro-ph/0508063
Autor:
Kiselman, Dan
The NLTE effects affecting oxygen-abundance determinations of solar-type stars are discussed. LTE is perfectly safe for the forbidden lines. The permitted triplet at 777 nm is expected to show NLTE effects on the order of a few tenths of a dex (alway
Externí odkaz:
http://arxiv.org/abs/astro-ph/0010300
Autor:
Kiselman, Dan
NLTE effects - the errors caused by assuming local thermodynamic equilibrium (LTE) - on LiBeB abundance determinations for cool stars are discussed. These NLTE effects are significant in many cases for B I and Li I lines. The Be II 313 nm lines are n
Externí odkaz:
http://arxiv.org/abs/astro-ph/9902375
Autor:
Kiselman, Dan
The astrophysically very interesting Li I 671 nm line has been observed with high spatial resolution in solar granulation with the intention to diagnose departures from local thermodynamic equilibrium (LTE) in the line formation. The spectral feature
Externí odkaz:
http://arxiv.org/abs/astro-ph/9802049