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Register a new userProbing the atmosphere of WASP-69 b with low- and high-resolution transmission spectroscopy
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Consideration of both low- and high-resolution transmission spectroscopy is key for obtaining a comprehensive picture of exoplanet atmospheres. In studies of transmission spectra, the continuum information is well established with low-resolution spectra, while the shapes of individual lines are best constrained with high-resolution observations. In this work, we aim to merge high- with low-resolution transmission spectroscopy. We present the analysis of three primary transits of WASP-69b in the VIS channel of the CARMENES instrument and perform a combined low- and high-resolution analysis using additional data from HARPS-N, OSIRIS/GTC, and WFC3/HST already available in the literature. During the first CARMENES observing night, we detected the planet Na D$_{2}$ and D$_{1}$ lines at $sim 7sigma$ and $sim 3sigma$ significance levels, respectively. We measured a D$_{2}$/D$_{1}$ intensity ratio of 2.5$pm$0.7, which is in agreement with previous HARPS-N observations. Our modelling of WFC3 and OSIRIS data suggests strong Rayleigh scattering, solar to super-solar water abundance, and a highly muted Na feature in the atmosphere of this planet, in agreement with previous investigations of this target. We use the continuum information retrieved from the low-resolution spectroscopy as a prior to break the degeneracy between the Na abundance, reference pressure, and thermosphere temperature for the high-resolution spectroscopic analysis. We fit the Na D$_{1}$ and D$_{2}$ lines individually and find that the posterior distributions of the model parameters agree with each other within 1$sigma$. Our results suggest that local thermodynamic equilibrium processes can explain the observed D$_{2}$/D$_{1}$ ratio because the presence of haze opacity mutes the absorption features.
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High-resolution transmission spectroscopy is a method for understanding the chemical and physical properties of upper exoplanetary atmospheres. Due to large absorption cross-sections, resonance lines of atomic sodium D-lines (at 5889.95 $AA$ and 5895.92 $AA$) produce large transmission signals. Our aim is to unveil the physical properties of WASP-17b through an accurate measurement of the sodium absorption in the transmission spectrum. We analyze 37 high-resolution spectra observed during a single transit of WASP-17b with the MIKE instrument on the 6.5 meter Magellan Telescopes. We exclude stellar flaring activity during the observations by analyzing the temporal variations of H$_{alpha}$ and Ca II infra-red triplet (IRT) lines. Then we obtain the excess absorption light curves in wavelength bands of 0.75, 1, 1.5 and 3 $AA$ around the center of each sodium line (i.e., the light curve approach). We model the effects of differential limb-darkening, and the changing planetary radial velocity on the light curves. We also analyze the sodium absorption directly in the transmission spectrum, which is obtained through dividing in-transit by out-of-transit spectra (i.e., the division approach). We then compare our measurements with a radiative transfer atmospheric model. Our analysis results in a tentative detection of exoplanetary sodium: we measure the width and amplitude of the exoplanetary sodium feature to be $sigma_{mathrm{Na}}$ = (0.128 $pm$ 0.078) $AA$ and A$_{mathrm{Na}}$ = (1.7 $pm$ 0.9)% in the excess light curve approach and $sigma_{mathrm{Na}}$ = (0.850 $pm$ 0.034) $AA$ and A$_{mathrm{Na}}$ = (1.3 $pm$ 0.6)% in the division approach. By comparing our measurements with a simple atmospheric model, we retrieve an atmospheric temperature of 1550 $^{+170} _{-200}$ K and radius (at 0.1 bar) of 1.81 $pm$ 0.02 R$_{rm Jup}$ for WASP-17b.
Aims. We report on ESPRESSO high-resolution transmission spectroscopic observations of two primary transits of the highly-irradiated, ultra-hot Jupiter-size planet WASP-76b. We investigate the presence of several key atomic and molecular features of interest that may reveal the atmospheric properties of the planet. Methods. We extracted two transmission spectra of WASP-76b with R approx 140,000 using a procedure that allowed us to process the full ESPRESSO wavelength range (3800-7880 A) simultaneously. We observed that at a high signal-to-noise ratio, the continuum of ESPRESSO spectra shows wiggles that are likely caused by an interference pattern outside the spectrograph. To search for the planetary features, we visually analysed the extracted transmission spectra and cross-correlated the observations against theoretical spectra of different atomic and molecular species. Results. The following atomic features are detected: Li I, Na I, Mg I, Ca II, Mn I, K I, and Fe I. All are detected with a confidence level between 9.2 sigma (Na I) and 2.8 sigma (Mg I). We did not detect the following species: Ti I, Cr I, Ni I, TiO, VO, and ZrO. We impose the following 1 sigma upper limits on their detectability: 60, 77, 122, 6, 8, and 8 ppm, respectively. Conclusions. We report the detection of Li I on WASP-76b for the first time. In addition, we found the presence of Na I and Fe I as previously reported in the literature. We show that the procedure employed in this work can detect features down to the level of ~ 0.1 % in the transmission spectrum and ~ 10 ppm by means of a cross-correlation method. We discuss the presence of neutral and singly ionised features in the atmosphere of WASP-76b.
We report detections of atomic species in the atmosphere of MASCARA-2 b, using the first transit observations obtained with the newly commissioned EXPRES spectrograph. EXPRES is a highly stabilised optical echelle spectrograph, designed to detect stellar reflex motions with amplitudes down to 30 cm/s, and was recently deployed at the Lowell Discovery Telescope. By analysing the transmission spectrum of the ultra-hot Jupiter MASCARA-2 b using the cross-correlation method, we confirm previous detections of Fe I, Fe II and Na I, which likely originate in the upper regions of the inflated atmosphere. In addition, we report significant detections of Mg I and Cr II. The absorption strengths change slightly with time, possibly indicating different temperatures and chemistry in the day-side and night-side terminators. Using the effective stellar line-shape variation induced by the transiting planet, we constrain the projected spin-orbit misalignment of the system to $1.6pm3.1$ degrees, consistent with an aligned orbit. We demonstrate that EXPRES joins a suite of instruments capable of phase-resolved spectroscopy of exoplanet atmospheres.
Thermal
Ultra-hot Jupiters (UHJs) present excellent targets for atmospheric characterisation. Their hot dayside temperatures (T $gtrsim$ 2200 K) strongly suppress the formation of condensates, leading to clear and highly-inflated atmospheres extremely conducive to transmission spectroscopy. Recent studies using optical high-resolution spectra have discovered a plethora of neutral and ionised atomic species in UHJs, placing constraints on their atmospheric structure and composition. Our recent work has presented a search for molecular features and detection of Fe I in the UHJ WASP-121b using VLT/UVES transmission spectroscopy. Here, we present a systematic search for atomic species in its atmosphere using cross-correlation methods. In a single transit, we uncover potential signals of 17 atomic species which we investigate further, categorising 5 as strong detections, 3 as tentative detections, and 9 as weak signals worthy of further exploration. We confirm previous detections of Cr I, V I, Ca I, K I and exospheric H I and Ca II made with HARPS and ESPRESSO, and independently re-recover our previous detection of Fe I at 8.8 $sigma$ using both the blue and red arms of the UVES data. We also add a novel detection of Sc II at 4.2 $sigma$. Our results further demonstrate the richness of UHJs for optical high-resolution spectroscopy.
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