The GTC exoplanet transit spectroscopy survey

Chen, G.; Guenther, E. W.; Pallé, E.; Nortmann, L.; Nowak, G.; Kunz, Sebastian; Parviainen, H.; Murgas, F.

doi:10.1051/0004-6361/201630228

Cited by 43 publications

(38 citation statements)

References 69 publications

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“…For both spatial and dispersion directions, the positions of spectra remained well within 1 pixel. We did not find any significant rotator-angle-dependent systematics as reported in previous observations (e.g., Nortmann et al 2016;Chen et al 2016Chen et al , 2017, probably because this observation only covered a small range of rotator angles (−229…”

Section: Observations and Data Reductionsupporting

confidence: 61%

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The GTC exoplanet transit spectroscopy survey

Chen

Πάλλη

Nortmann

et al. 2017

A&A

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We report the first detection of sodium absorption in the atmosphere of the hot Jupiter WASP-52b. We observed one transit of WASP-52b with the low-resolution Optical System for Imaging and low-Intermediate-Resolution Integrated Spectroscopy (OSIRIS) at the 10.4 m Gran Telescopio Canarias (GTC). The resulting transmission spectrum, covering the wavelength range from 522 nm to 903 nm, is flat and featureless, except for the significant narrow absorption signature at the sodium doublet, which can be explained by an atmosphere in solar composition with clouds at 1 mbar. A cloud-free atmosphere is stringently ruled out. By assessing the absorption depths of sodium in various bin widths, we find that temperature increases towards lower atmospheric pressure levels, with a positive temperature gradient of 0.88 ± 0.65 K km −1 , possibly indicative of upper atmospheric heating and a temperature inversion.

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Section: Observations and Data Reductionsupporting

confidence: 61%

“…We reduced the OSIRIS data using the approach outlined in Chen et al (2016Chen et al ( , 2017. The one-dimensional spectra (see Fig.…”

Section: Observations and Data Reductionmentioning

confidence: 99%

The GTC exoplanet transit spectroscopy survey

Chen

Πάλλη

Nortmann

et al. 2017

A&A

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“…8, the density of K2-106 c is consistent with a planet composed of 50% rock and 50% ice. However, as pointed out above, other planets like this one consist of a rocky core with a hydrogen atmosphere (Chen et al 2017). Since the mass is M c = 5.8 +3.3 −3.0 M ⊕ and the ratio of the stellar flux received by the planet compared to Earth is F p /F ⊕ ∼ 52, there is no reason why it could not have a hydrogen atmosphere since at about 800 K a 50% ice content is not very plausible.…”

Section: Discussionmentioning

confidence: 86%

“…It is obvious that the planets with the highest densities must be rocky, while those with the lowest densities must have a large fraction of volatiles such as hydrogen. Planets of intermediate densities could in principle have many different compositions, but there is now growing evidence that they also have rocky cores and less extended hydrogen atmospheres (see, for example, Chen et al 2017). A picture has thus emerged in which the diversity of low-mass exoplanets is explained by the different size of the hydrogen atmospheres -some planets have very extended atmospheres, some have less extended ones, and others do not have them at all.…”

Section: Introductionmentioning

confidence: 99%

K2-106, a system containing a metal-rich planet and a planet of lower density

Guenther

Barragán

Dai

et al. 2017

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Aims. Planets in the mass range from 2 to 15 M ⊕ are very diverse. Some of them have low densities, while others are very dense. By measuring the masses and radii, the mean densities, structure, and composition of the planets are constrained. These parameters also give us important information about their formation and evolution, and about possible processes for atmospheric loss. Methods. We determined the masses, radii, and mean densities for the two transiting planets orbiting K2-106. The inner planet has an ultra-short period of 0.57 days. The period of the outer planet is 13.3 days. . Conclusions. Since the system contains two planets of almost the same mass, but different distances from the host star, it is an excellent laboratory to study atmospheric escape. In agreement with the theory of atmospheric-loss processes, it is likely that the outer planet has a hydrogen-dominated atmosphere. The mass and radius of the inner planet is in agreement with theoretical models predicting an iron core containing 80 +20 −30 % of its mass. Such a high metal content is surprising, particularly given that the star has an ordinary (solar) metal abundance. We discuss various possible formation scenarios for this unusual planet.

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“…The passband-integrated light curves are produced from the raw data using the pipeline described in Chen et al (2016Chen et al ( , 2017. The pipeline carries out the basic CCD data reduction steps, calculates a 2D wavelength solution, removes the sky, and generates a reduced 1D spectrum for WASP-80 and the comparison star (Fig.…”

Section: Data Reduction and Passband Setsmentioning

confidence: 99%

The GTC exoplanet transit spectroscopy survey

Parviainen

Pallé

Chen

et al. 2018

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Aims. We set out to study the atmosphere of WASP-80b, a warm inflated gas giant with an equilibrium temperature of ∼800 K, using ground-based transmission spectroscopy covering the spectral range from 520 to 910 nm. The observations allow us to probe the existence and abundance of K and Na in WASP-80b's atmosphere, existence of high-altitude clouds, and Rayleigh-scattering in the blue end of the spectrum. Methods. We observed two spectroscopic time series of WASP-80b transits with the OSIRIS spectrograph installed in the Gran Telescopio CANARIAS, and use the observations to estimate the planet's transmission spectrum between 520 nm and 910 nm in 20 nm-wide passbands, and around the K I and Na I resonance doublets in 6 nm-wide passbands. We model three previously published broadband datasets consisting of 27 light curves jointly prior to the transmission spectroscopy analysis in order to obtain improved prior estimates for the planet's orbital parameters, average radius ratio, and stellar density. The parameter posteriors from the broadband analysis are used to set informative priors on the transmission spectroscopy analysis. The final transmission spectroscopy analyses are carried out jointly for the two nights using a divide-by-white approach to remove the common-mode systematics and Gaussian processes to model the residual wavelength-dependent systematics. Results. We recover a flat transmission spectrum with no evidence of Rayleigh scattering or K I or Na I absorption, and obtain an improved system characterisation as a by-product of the broadband-and GTC-dataset modelling. The transmission spectra estimated separately from the two observing runs are consistent with each other, as are the transmission spectra estimated using either a parametric or nonparametric systematics models. The flat transmission spectrum favours an atmosphere model with high-altitude clouds over cloud-free models with stellar or sub-stellar metallicities. Conclusions. Our results disagree with the recently published discovery of strong K I absorption in WASP-80b's atmosphere based on ground-based transmission spectroscopy with FORS2 at VLT.

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The GTC exoplanet transit spectroscopy survey

Cited by 43 publications

References 69 publications

The GTC exoplanet transit spectroscopy survey

The GTC exoplanet transit spectroscopy survey

K2-106, a system containing a metal-rich planet and a planet of lower density

The GTC exoplanet transit spectroscopy survey

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