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Spatially resolved spectroscopy across stellar surfaces : IV. F, G, and K-stars: Synthetic 3D spectra at hyper-high resolution

Dravins, Dainis LU orcid ; Ludwig, Hans Günter LU and Freytag, Bernd (2021) In Astronomy and Astrophysics 649.
Abstract

Context. High-precision stellar analyses require hydrodynamic 3D modeling. Such models predict changes across stellar disks of spectral line shapes, asymmetries, and wavelength shifts. For testing models in stars other than the Sun, spatially resolved observations are feasible from differential spectroscopy during exoplanet transits, retrieving spectra of those stellar surface segments that successively become hidden behind the transiting planet, as demonstrated in Papers I, II, and III. Aims. Synthetic high-resolution spectra over extended spectral regions are now available from 3D models. Similar to other ab initio simulations in astrophysics, these data contain patterns that have not been specifically modeled but may be revealed... (More)

Context. High-precision stellar analyses require hydrodynamic 3D modeling. Such models predict changes across stellar disks of spectral line shapes, asymmetries, and wavelength shifts. For testing models in stars other than the Sun, spatially resolved observations are feasible from differential spectroscopy during exoplanet transits, retrieving spectra of those stellar surface segments that successively become hidden behind the transiting planet, as demonstrated in Papers I, II, and III. Aims. Synthetic high-resolution spectra over extended spectral regions are now available from 3D models. Similar to other ab initio simulations in astrophysics, these data contain patterns that have not been specifically modeled but may be revealed after analyses to be analogous to those of a large volume of observations. Methods. From five 3D models spanning Teff = 3964-6726 K (spectral types ~K8 V-F3 V), synthetic spectra at hyper-high resolution (λ/Δλ >1 000 000) were analyzed. Selected Fe » I and Fe » II lines at various positions across stellar disks were searched for characteristic patterns between different types of lines in the same star and for similar lines between different stars. Results. Spectral-line patterns are identified for representative photospheric lines of different strengths, excitation potentials, and ionization levels, thereby encoding the hydrodynamic 3D structure. Line profiles and bisectors are shown for various stars at different positions across stellar disks. Absolute convective wavelength shifts are obtained as differences to 1D models, where such shifts do not occur. Conclusions. Observable relationships for line properties are retrieved from realistically complex synthetic spectra. Such patterns may also test very detailed 3D modeling, including non-LTE effects. While present results are obtained at hyper-high spectral resolution, the subsequent Paper V examines their practical observability at realistically lower resolutions, and in the presence of noise.

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author
; and
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Line: profiles, Methods: observational, Stars: atmospheres, Stars: solar-type, Techniques: radial velocities, Techniques: spectroscopic
in
Astronomy and Astrophysics
volume
649
article number
A16
publisher
EDP Sciences
external identifiers
  • scopus:85104963679
ISSN
0004-6361
DOI
10.1051/0004-6361/202039995
language
English
LU publication?
yes
id
ad3a07ef-7da1-494c-a9d8-a461708d78d6
date added to LUP
2021-05-17 15:05:44
date last changed
2024-04-20 06:13:33
@article{ad3a07ef-7da1-494c-a9d8-a461708d78d6,
  abstract     = {{<p>Context. High-precision stellar analyses require hydrodynamic 3D modeling. Such models predict changes across stellar disks of spectral line shapes, asymmetries, and wavelength shifts. For testing models in stars other than the Sun, spatially resolved observations are feasible from differential spectroscopy during exoplanet transits, retrieving spectra of those stellar surface segments that successively become hidden behind the transiting planet, as demonstrated in Papers I, II, and III. Aims. Synthetic high-resolution spectra over extended spectral regions are now available from 3D models. Similar to other ab initio simulations in astrophysics, these data contain patterns that have not been specifically modeled but may be revealed after analyses to be analogous to those of a large volume of observations. Methods. From five 3D models spanning Teff = 3964-6726 K (spectral types ~K8 V-F3 V), synthetic spectra at hyper-high resolution (λ/Δλ &gt;1 000 000) were analyzed. Selected Fe » I and Fe » II lines at various positions across stellar disks were searched for characteristic patterns between different types of lines in the same star and for similar lines between different stars. Results. Spectral-line patterns are identified for representative photospheric lines of different strengths, excitation potentials, and ionization levels, thereby encoding the hydrodynamic 3D structure. Line profiles and bisectors are shown for various stars at different positions across stellar disks. Absolute convective wavelength shifts are obtained as differences to 1D models, where such shifts do not occur. Conclusions. Observable relationships for line properties are retrieved from realistically complex synthetic spectra. Such patterns may also test very detailed 3D modeling, including non-LTE effects. While present results are obtained at hyper-high spectral resolution, the subsequent Paper V examines their practical observability at realistically lower resolutions, and in the presence of noise. </p>}},
  author       = {{Dravins, Dainis and Ludwig, Hans Günter and Freytag, Bernd}},
  issn         = {{0004-6361}},
  keywords     = {{Line: profiles; Methods: observational; Stars: atmospheres; Stars: solar-type; Techniques: radial velocities; Techniques: spectroscopic}},
  language     = {{eng}},
  month        = {{05}},
  publisher    = {{EDP Sciences}},
  series       = {{Astronomy and Astrophysics}},
  title        = {{Spatially resolved spectroscopy across stellar surfaces : IV. F, G, and K-stars: Synthetic 3D spectra at hyper-high resolution}},
  url          = {{http://dx.doi.org/10.1051/0004-6361/202039995}},
  doi          = {{10.1051/0004-6361/202039995}},
  volume       = {{649}},
  year         = {{2021}},
}