The GAPS programme at TNG

Abstract

Context. Transiting ultra-hot Jupiters are ideal candidates for studying the exoplanet atmospheres and their dynamics, particularly by means of high-resolution spectra with high signal-to-noise ratios. One such object is KELT-20b. It orbits the fast-rotating A2-type star KELT-20. Many atomic species have been found in its atmosphere, with blueshifted signals that indicate a day- to night-side wind. Aims. We observe the atmospheric Rossiter-McLaughlin effect in the ultra-hot Jupiter KELT-20b and study any variation of the atmospheric signal during the transit. For this purpose, we analysed five nights of HARPS-N spectra covering five transits of KELT-20b. Methods. We computed the mean line profiles of the spectra with a least-squares deconvolution using a stellar mask obtained from the Vienna Atomic Line Database (Teff = 10 000 K, log g = 4.3), and then we extracted the stellar radial velocities by fitting them with a rotational broadening profile in order to obtain the radial velocity time-series. We used the mean line profile residuals tomography to analyse the planetary atmospheric signal and its variations. We also used the cross-correlation method to study a previously reported double-peak feature in the FeI planetary signal. Results. We observed both the classical and the atmospheric Rossiter-McLaughlin effect in the radial velocity time-series. The latter gave us an estimate of the radius of the planetary atmosphere that correlates with the stellar mask used in our work (Rp+atmo∕Rp = 1.13 ± 0.02). We isolated the planetary atmospheric trace in the tomography, and we found radial velocity variations of the planetary atmospheric signal during transit with an overall blueshift of ≈10 km s−1, along with small variations in the signal depth, and less significant, in the full width at half maximum (FWHM). We also find a possible variation in the structure and position of the FeI signal in different transits. Conclusions. We confirm the previously detected blueshift of the atmospheric signal during the transit. The FWHM variations of the atmospheric signal, if confirmed, may be caused by more turbulent condition at the beginning of the transit, by a variable contribution of the elements present in the stellar mask to the overall planetary atmospheric signal, or by iron condensation. The FeI signal show indications of variability from one transit to the next.

The GAPS Programme with HARPS-N at TNG. XXXI. The WASP-33 system revisited with HARPS-N

“…Although stellar pulsations dominate also the RV curve, it is evident a qualitative agreement with the theoretical RM curve calculated using the parameters presented in Table 2 (by using the formalism of Ohta et al 2005). This is a further confirmation that for fast rotators the method of fitting the mean line profiles with a rotational profile instead of a Gaussian function brings optimal results, as it was previously found for other targets (e.g., Anderson et al 2018;Johnson et al 2018;Borsa et al 2019;Rainer et al 2021). We note however that for this case the Doppler tomography method remains the preferred one to determine the projected spin-orbit inclination angle.…”

Detection of iron emission lines and a temperature inversion on the dayside of the ultra-hot Jupiter KELT-20b

“…In addition to the emission spectroscopy, Fe i has also been detected in the transmission spectrum of KELT-20b. The Fe i transmission spectrum is blueshifted by 5 -10 km s −1 and the signal has an asymmetric feature between the first and second half of the transit (Stangret et al 2020;Nugroho et al 2020b;Hoeijmakers et al 2020;Rainer et al 2021), probably caused by atmospheric dynamics.…”

“…Here, we report the detection of Fe i emission lines in the dayside spectrum of KELT-20b/MASCARA-2b. The planet is an ultra-hot Jupiter with an equilibrium temperature (T eq ) of ∼ 2300 K. The transmission spectrum of the planet has been observed with several different instruments and various spectral features have been detected, including hydrogen Balmer lines, Fe i, Fe ii, Na i, Ca ii, Mg i, and Cr ii (Casasayas- Barris et al 2018Stangret et al 2020;Nugroho et al 2020b;Hoeijmakers et al 2020;Kesseli et al 2020;Rainer et al 2021). We present the first thermal emission spectroscopy of this planet.…”

Silicon in the dayside atmospheres of two ultra-hot Jupiters

“…KELT-20b/MASCARA-2b (Lund et al 2017;Talens et al 2018) is a UHJ with T eq ∼ 2300 K that orbits an A-type star without pulsations. A number of metals, such as Ca, Cr, Fe, Na, and Mg, were found in the planetary transmission spectrum (Casasayas-Barris et al 2018Hoeijmakers et al 2020a;Stangret et al 2020;Nugroho et al 2020b;Rainer et al 2021). Recently, Yan et al (2021a) used the spectral emission lines of Fe i to retrieve the atmospheric temperature profile, claiming the presence of a temperature inversion on the planetary dayside.…”