Time-resolved UVES observations of a stellar flare on the planet host HD 189733 during primary transit

Klocová, T.; Czesla, S.; Khalafinejad, S.; Wolter, Uwe; Schmitt, J. H. M. M.

doi:10.1051/0004-6361/201630068

Cited by 24 publications

(16 citation statements)

References 79 publications

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“…The Ca II-IR triplet lines are known to show variations due to stellar chromospheric activity. Klocová et al (2017) investigated a flare during one transit of HD189733b determining a change in flux of the Ca II line at 8498 Å of around 2-3 per cent (see their fig. 6).…”

Section: Re-investigating the K I Absorption On Hd189733bmentioning

confidence: 99%

Probing the atmosphere of HD189733b with the Na i and K i lines

Keles

Kitzmann

Mallonn

et al. 2020

Monthly Notices of the Royal Astronomical Society

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High spectral resolution transmission spectroscopy is a powerful tool to characterize exoplanet atmospheres. Especially for hot Jupiters, this technique is highly relevant, due to their high altitude absorption e.g. from resonant sodium (Na i) and potassium (K i) lines. We resolve the atmospheric K i-absorption on HD189733b with the aim to compare the resolved K i-line and previously obtained high resolution Na i-D-line observations with synthetic transmission spectra. The line profiles suggest atmospheric processes leading to a line broadening of the order of ∼10 km/s for the Na i-D-lines, and only a few km/s for the K i-line. The investigation hints that either the atmosphere of HD189733b lacks a significant amount of K i or the alkali lines probe different atmospheric regions with different temperature, which could explain the differences we see in the resolved absorption lines.

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Section: Re-investigating the K I Absorption On Hd189733bmentioning

confidence: 99%

Probing the atmosphere of HD189733b with the Na i and K i lines

Keles

Kitzmann

Mallonn

et al. 2020

Monthly Notices of the Royal Astronomical Society

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“…The presence of stellar activity offers both opportunities and problems. Precision photometry during transit suggests that the planet sometimes crosses some dark spots (Pont et al 2007;Sing et al 2011), while bright flares may appear in chromospheric emission lines (Czesla et al 2015;Klocová et al 2017). A challenging future task will be to recover spatially resolved spectra of such starspots and active regions (including their magnetic signatures), but that will require simultaneous sequences of precision photometry and spectroscopy, which are not yet available.…”

Section: Stellar Activitymentioning

confidence: 99%

Spatially resolved spectroscopy across stellar surfaces

Dravins

Gustavsson

Ludwig

2018

A&A

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Context. Spectroscopy across spatially resolved stellar surfaces reveals spectral line profiles free from rotational broadening, whose gradual changes from disk center toward the stellar limb reflect an atmospheric fine structure that is possible to model by 3D hydrodynamics. Aims. Previous studies of photospheric spectral lines across stellar disks exist for the Sun and HD 209458 (G0 V) and are now extended to the planet-hosting HD 189733A to sample a cooler K-type star and explore the future potential of the method. Methods. During exoplanet transit, stellar surface portions successively become hidden and differential spectroscopy between various transit phases uncovers spectra of small surface segments temporarily hidden behind the planet. The method was elaborated in Paper I, in which observable signatures were predicted quantitatively from hydrodynamic simulations. Results. From observations of HD 189733A with the ESO HARPS spectrometer at λ/Δλ~ 115 000, profiles for stronger and weaker Fe I lines are retrieved at several center-to-limb positions, reaching adequate S/N after averaging over numerous similar lines. Conclusions. Retrieved line profile widths and depths are compared to synthetic ones from models with parameters bracketing those of the target star and are found to be consistent with 3D simulations. Center-to-limb changes strongly depend on the surface granulation structure and much greater line-width variation is predicted in hotter F-type stars with vigorous granulation than in cooler K-types. Such parameters, obtained from fits to full line profiles, are realistic to retrieve for brighter planet-hosting stars, while their hydrodynamic modeling offers previously unexplored diagnostics for stellar atmospheric fine structure and 3D line formation. Precise modeling may be required in searches for Earth-analog exoplanets around K-type stars, whose more tranquil surface granulation and lower ensuing microvariability may enable such detections.

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“…Other stars are far less intensively monitored with highresolution spectroscopy than the Sun, so that spectral time series of stellar flares often result from chance observations (e.g. Klocová et al 2017). Also, flares on other stars are generally only observed in disk-integrated light.…”

Section: Introductionmentioning

confidence: 99%

The CARMENES search for exoplanets around M dwarfs

Fuhrmeister

Czesla

Schmitt

et al. 2018

A&A

Self Cite

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Stellar activity is ubiquitously encountered in M dwarfs and often characterised by the Hα line. In the most active M dwarfs, Hα is found in emission, sometimes with a complex line profile. Previous studies have reported extended wings and asymmetries in the Hα line during flares. We used a total of 473 high-resolution spectra of 28 active M dwarfs obtained by the CARMENES (Calar Alto high-Resolution search for M dwarfs with Exo-Earths with Near-infrared and optical Echelle Spectrographs) spectrograph to study the occurrence of broadened and asymmetric Hα line profiles and their association with flares, and examine possible physical explanations. We detected a total of 41 flares and 67 broad, potentially asymmetric, wings in Hα. The broadened Hα lines display a variety of profiles with symmetric cases and both red and blue asymmetries. Although some of these line profiles are found during flares, the majority are at least not obviously associated with flaring. We propose a mechanism similar to coronal rain or chromospheric downward condensations as a cause for the observed red asymmetries; the symmetric cases may also be caused by Stark broadening. We suggest that blue asymmetries are associated with rising material, and our results are consistent with a prevalence of blue asymmetries during the flare onset. Besides the Hα asymmetries, we find some cases of additional line asymmetries in He I D3, Na I D lines, and the He I line at 10 830 Å taken all simultaneously thanks to the large wavelength coverage of CARMENES. Our study shows that asymmetric Hα lines are a rather common phenomenon in M dwarfs and need to be studied in more detail to obtain a better understanding of the atmospheric dynamics in these objects.

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Time-resolved UVES observations of a stellar flare on the planet host HD 189733 during primary transit

Cited by 24 publications

References 79 publications

Probing the atmosphere of HD189733b with the Na i and K i lines

Probing the atmosphere of HD189733b with the Na i and K i lines

Spatially resolved spectroscopy across stellar surfaces

The CARMENES search for exoplanets around M dwarfs

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