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Spatially resolved spectroscopy across stellar surfaces : II. High-resolution spectra across HD 209458 (G0 V)

Dravins, Dainis LU ; Ludwig, Hans Günter LU ; Dahlén, Sven-Erik and Pazira, Hiva (2017) In Astronomy and Astrophysics 605.
Abstract

Context. High-resolution spectroscopy across spatially resolved stellar surfaces aims at obtaining spectral-line profiles that are free from rotational broadening; the gradual changes of these profiles from disk center toward the stellar limb reveal properties of atmospheric fine structure, which are possible to model with 3D hydrodynamics. Aims. Previous such studies have only been carried out for the Sun but are now extended to other stars. In this work, profiles of photospheric spectral lines are retrieved across the disk of the planet-hosting star HD 209458 (G0 V). Methods. During exoplanet transit, stellar surface portions successively become hidden and differential spectroscopy provides spectra of small surface segments... (More)

Context. High-resolution spectroscopy across spatially resolved stellar surfaces aims at obtaining spectral-line profiles that are free from rotational broadening; the gradual changes of these profiles from disk center toward the stellar limb reveal properties of atmospheric fine structure, which are possible to model with 3D hydrodynamics. Aims. Previous such studies have only been carried out for the Sun but are now extended to other stars. In this work, profiles of photospheric spectral lines are retrieved across the disk of the planet-hosting star HD 209458 (G0 V). Methods. During exoplanet transit, stellar surface portions successively become hidden and differential spectroscopy provides spectra of small surface segments temporarily hidden behind the planet. The method was elaborated in Paper I, with observable signatures quantitatively predicted from hydrodynamic simulations. Results. From observations of HD 209458 with spectral resolution λ/ Δλ ~ 80 000, photospheric Fe I line profiles are obtained at several center-To-limb positions, reaching adequately high S/N after averaging over numerous similar lines. Conclusions. Retrieved line profiles are compared to synthetic line profiles. Hydrodynamic 3D models predict, and current observations confirm, that photospheric absorption lines become broader and shallower toward the stellar limb, reflecting that horizontal velocities in stellar granulation are greater than vertical velocities. Additional types of 3D signatures will become observable with the highest resolution spectrometers at large telescopes.

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organization
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type
Contribution to journal
publication status
published
subject
keywords
Hydrodynamics, Line: profiles, Planets and satellites: gaseous planets, Stars: Atmospheres, Stars: solar-Type, Techniques: spectroscopic
in
Astronomy and Astrophysics
volume
605
publisher
EDP Sciences
external identifiers
  • scopus:85029508215
  • wos:000412231200094
ISSN
0004-6361
DOI
10.1051/0004-6361/201730901
language
English
LU publication?
yes
id
6206e604-fb7c-4421-9f67-129406826124
date added to LUP
2017-10-02 12:58:30
date last changed
2018-02-25 04:19:41
@article{6206e604-fb7c-4421-9f67-129406826124,
  abstract     = {<p>Context. High-resolution spectroscopy across spatially resolved stellar surfaces aims at obtaining spectral-line profiles that are free from rotational broadening; the gradual changes of these profiles from disk center toward the stellar limb reveal properties of atmospheric fine structure, which are possible to model with 3D hydrodynamics. Aims. Previous such studies have only been carried out for the Sun but are now extended to other stars. In this work, profiles of photospheric spectral lines are retrieved across the disk of the planet-hosting star HD 209458 (G0 V). Methods. During exoplanet transit, stellar surface portions successively become hidden and differential spectroscopy provides spectra of small surface segments temporarily hidden behind the planet. The method was elaborated in Paper I, with observable signatures quantitatively predicted from hydrodynamic simulations. Results. From observations of HD 209458 with spectral resolution λ/ Δλ ~ 80 000, photospheric Fe I line profiles are obtained at several center-To-limb positions, reaching adequately high S/N after averaging over numerous similar lines. Conclusions. Retrieved line profiles are compared to synthetic line profiles. Hydrodynamic 3D models predict, and current observations confirm, that photospheric absorption lines become broader and shallower toward the stellar limb, reflecting that horizontal velocities in stellar granulation are greater than vertical velocities. Additional types of 3D signatures will become observable with the highest resolution spectrometers at large telescopes.</p>},
  articleno    = {A91},
  author       = {Dravins, Dainis and Ludwig, Hans Günter and Dahlén, Sven-Erik and Pazira, Hiva},
  issn         = {0004-6361},
  keyword      = {Hydrodynamics,Line: profiles,Planets and satellites: gaseous planets,Stars: Atmospheres,Stars: solar-Type,Techniques: spectroscopic},
  language     = {eng},
  month        = {09},
  publisher    = {EDP Sciences},
  series       = {Astronomy and Astrophysics},
  title        = {Spatially resolved spectroscopy across stellar surfaces : II. High-resolution spectra across HD 209458 (G0 V)},
  url          = {http://dx.doi.org/10.1051/0004-6361/201730901},
  volume       = {605},
  year         = {2017},
}