The IAG solar flux atlas: Accurate wavelengths and absolute convective blueshift in standard solar spectra

Reiners, A.; Mrotzek, Niclas; Lemke, Ulrike; Hinrichs, Johannes; Reinsch, K.

doi:10.1051/0004-6361/201527530

Cited by 98 publications

(158 citation statements)

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“…Such a telluric-free zone is just blueward of the O 2 A-band between 7517-7580 Å and contains over 20 well-defined and relatively unblended solar lines. We adopt the IAG FTS atlas from Reiners et al (2016) as a template and cross correlate all other spectra with it. The crosscorrelation peak is fit with a polynomial and returns one relative velocity.…”

Section: Identifying the Spectrum Componentsmentioning

confidence: 99%

“…Heliocentric radial velocities in m s −1 from the lunar Tycho region. The dots are our relative velocities from solar absorption lines with respect to the IAG FTS solar atlas(Reiners et al 2016). The colors denote the wavelengths at which the velocities were measured and are identified in the insert (CD is the cross disperser and its respective central wavelength in Å; symbols are dots = CD VI, squares = CD V, diamonds = CD IV, crosses = CD III, pluses = CD II).…”

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confidence: 99%

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High-resolution spectroscopy and spectropolarimetry of the total lunar eclipse January 2019

Strassmeier

Ilyin

Keles

et al. 2020

A&A

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Context. Observations of the Earthshine off the Moon allow for the unique opportunity to measure the large-scale Earth atmosphere. Another opportunity is realized during a total lunar eclipse which, if seen from the Moon, is like a transit of the Earth in front of the Sun. Aims. We thus aim at transmission spectroscopy of an Earth transit by tracing the solar spectrum during the total lunar eclipse of January 21, 2019. Methods. Time series spectra of the Tycho crater were taken with the Potsdam Echelle Polarimetric and Spectroscopic Instrument (PEPSI) at the Large Binocular Telescope (LBT) in its polarimetric mode in Stokes IQUV at a spectral resolution of 130 000 (0.06 Å). In particular, the spectra cover the red parts of the optical spectrum between 7419-9067 Å. The spectrograph's exposure meter was used to obtain a light curve of the lunar eclipse.Results. The brightness of the Moon dimmed by 10. m 75 during umbral eclipse. We found both branches of the O 2 A-band almost completely saturated as well as a strong increase of H 2 O absorption during totality. A pseudo O 2 emission feature remained at a wavelength of 7618 Å, but it is actually only a residual from different P-branch and R-branch absorptions. It nevertheless traces the eclipse. The deep penumbral spectra show significant excess absorption from the Na i 5890-Å doublet, the Ca ii infrared triplet around 8600 Å, and the K i line at 7699 Å in addition to several hyper-fine-structure lines of Mn i and even from Ba ii. The detections of the latter two elements are likely due to an untypical solar center-to-limb effect rather than Earth's atmosphere. The absorption in Ca ii and K i remained visible throughout umbral eclipse. Our radial velocities trace a wavelength dependent Rossiter-McLaughlin effect of the Earth eclipsing the Sun as seen from the Tycho crater and thereby confirm earlier observations. A small continuum polarization of the O 2 A-band of 0.12 % during umbral eclipse was detected at 6.3σ. No line polarization of the O 2 A-band, or any other spectral-line feature, is detected outside nor inside eclipse. It places an upper limit of ≈0.2% on the degree of line polarization during transmission through Earth's atmosphere and magnetosphere.

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Section: Identifying the Spectrum Componentsmentioning

confidence: 99%

mentioning

confidence: 99%

High-resolution spectroscopy and spectropolarimetry of the total lunar eclipse January 2019

Strassmeier

Ilyin

Keles

et al. 2020

A&A

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“…An example of how changing telluric absorption in the wings of Hα, such as that shown in Fig. 1 of Reiners et al (2016), causes a spurious "emission" in the reconstructed profile, is in Fig. 9 of Dravins et al (2015).…”

Section: Chromospheric Linesmentioning

confidence: 99%

Spatially resolved spectroscopy across stellar surfaces

Dravins

Ludwig

Dahlén

et al. 2017

A&A

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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/∆λ ∼ 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.Key words. stars: atmospheres -techniques: spectroscopic -line: profiles -hydrodynamics -planets and satellites: gaseous planetsstars: solar-type Spatially resolved stellar spectraThree-dimensional and time-dependent hydrodynamic simulations provide realistic descriptions of the atmospheres of various classes of stars, and spectra computed from such models can be used to determine precise properties of the star and its exoplanets. To constrain and evolve such models, observations beyond the ordinary spectrum of integrated starlight are desirable. Spectral-line syntheses in 3D atmospheres show a rich variety of phenomena characterizing stellar hydrodynamics, which are seen especially in the gradual changes of photospheric line profile strengths, shapes, asymmetries, and wavelength shifts from the center of the disk toward the stellar limb. However, direct comparisons between theory and spectral-line observations have in the past only been possible for the spatially resolved Sun (e.g., Lind et al. 2017). In Paper I (Dravins et al. 2017), we examined theoretically predicted spatially resolved signatures for a group of main-sequence stellar models with temperatures between 6730 and 3960 K. Corresponding observations are feasible during exoplanet transits when small stellar surface portions successively become hidden, and differential spectroscopy between different transit phases can provide spectra of small surface segments temporarily hidden behind the pla...

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“…3). Studies of the solar spectrum under more stellar-like conditions include signatures in integrated sunlight during a transit of Venus and during a partial solar eclipse (Reiners et al 2016a), of convective line shifts and line asymmetries (de la Cruz Rodríguez et al 2011;Dravins 2008;Molaro & Monai 2012;Reiners et al 2016b), center-tolimb changes of line profile shapes (Koesterke et al 2008), and temporal variability of line profiles and bisectors in diskintegrated sunlight (Dumusque et al 2015;Marchwinski et al 2015).…”

Section: Spatially Resolved Diagnosticsmentioning

confidence: 99%

Spatially resolved spectroscopy across stellar surfaces

Dravins

Ludwig

Dahlén

et al. 2017

A&A

View full text Add to dashboard Cite

Context. High-precision stellar analyses require hydrodynamic modeling to interpret chemical abundances or oscillation modes. Exoplanet atmosphere studies require stellar background spectra to be known along the transit path while detection of Earth analogs require stellar microvariability to be understood. Hydrodynamic 3D models can be computed for widely different stars but have been tested in detail only for the Sun with its resolved surface features. Model predictions include spectral line shapes, asymmetries, and wavelength shifts, and their center-to-limb changes across stellar disks. Aims. We observe high-resolution spectral line profiles across spatially highly resolved stellar surfaces, which are free from the effects of spatial smearing and rotational broadening present in full-disk spectra, enabling comparisons to synthetic profiles from 3D models. Methods. During exoplanet transits, successive stellar surface portions become hidden and differential spectroscopy between various transit phases provides spectra of small surface segments temporarily hidden behind the planet. Planets cover no more than ∼1% of any main-sequence star, enabling high spatial resolution but demanding very precise observations. Realistically measurable quantities are identified through simulated observations of synthetic spectral lines. Results. In normal stars, line profile ratios between various transit phases may vary by ∼0.5%, requiring S /N 5000 for meaningful spectral reconstruction.While not yet realistic for individual spectral lines, this is achievable for cool stars by averaging over numerous lines with similar parameters. Conclusions. For bright host stars of large transiting planets, spatially resolved spectroscopy is currently practical. More observable targets are likely to be found in the near future by ongoing photometric searches.

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The IAG solar flux atlas: Accurate wavelengths and absolute convective blueshift in standard solar spectra

Cited by 98 publications

References 20 publications

High-resolution spectroscopy and spectropolarimetry of the total lunar eclipse January 2019

High-resolution spectroscopy and spectropolarimetry of the total lunar eclipse January 2019

Spatially resolved spectroscopy across stellar surfaces

Spatially resolved spectroscopy across stellar surfaces

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