A Survey of Alkali Line Absorption in Exoplanetary Atmospheres

Abstract

We obtained over 90 hours of spectroscopic observations of four exoplanetary systems with the Hobby-Eberly Telescope (HET). Observations were taken in transit and out of transit, and we analyzed the differenced spectra---i.e., the transmission spectra---to inspect it for absorption at the wavelengths of the neutral sodium (\ion{Na}{1}) doublet at $\lambda \lambda 5889,5895$ and neutral potassium (\ion{K}{1}) at $\lambda 7698$. We used the transmission spectrum at \ion{Ca}{1} $\lambda 6122$---which shows strong stellar absorption but is not an alkali metal resonance line that we expect to show significant absorption in these atmospheres---as a control line to examine our measurements for systematic errors. We use an empirical Monte Carlo method to quantity these systematic errors. In a reanalysis of the same dataset using a reduction and analysis pipeline that was derived independently, we confirm the previously seen \ion{Na}{1} absorption in HD 189733b at a level of $(-5.26\pm 1.69)\times 10^{-4}$ (the average value over a 12 Å integration band to be consistent with previous authors). Additionally, we tentatively confirm the \ion{Na}{1} absorption seen in HD 209458b (independently by multiple authors) at a level of $(-2.63\pm 0.81)\times 10^{-4}$, though the interpretation is less clear. Furthermore, we find \ion{Na}{1} absorption of $(-3.16\pm 2.06)\times 10^{-4}$ at $<3\sigma$ in HD 149026b; features apparent in the transmission spectrum are consistent with real absorption and indicate this may be a good target for future observations to confirm. No other results (\ion{Na}{1} in HD 147506b and \ion{Ca}{1} and \ion{K}{1} in all four targets) are significant to $\ge 3\sigma$, although we observe some features that we argue are primarily artifacts.

38 total pages (preprint format), 9 color figures, 4 tables, accepted for publication in ApJ

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• HST hot Jupiter Transmission Spectral Survey: A detection of Na and strong optical absorption in HAT-P-1b
• Temperature-Pressure Profile of the hot Jupiter HD 189733b from HST Sodium Observations: Detection of Upper Atmospheric Heating
• An HST Optical to Near-IR Transmission Spectrum of the Hot Jupiter WASP-19b: Detection of Atmospheric Water and Likely Absence of TiO
• Spatially resolved eastward winds and rotation of HD 189733b
• ACCESS I: An Optical Transmission Spectrum of GJ 1214b Reveals a Heterogeneous Stellar Photosphere
• Constraining High Speed Winds in Exoplanet Atmospheres Through Observations of Anomalous Doppler Shifts During Transit
• Hot Exoplanet Atmospheres Resolved with Transit Spectroscopy (HEARTS) - II. A broadened sodium feature on the ultra-hot giant WASP-76b
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• Hot Exoplanet Atmospheres Resolved with Transit Spectroscopy (HEARTS) I. Detection of hot neutral sodium at high altitudes on WASP-49b
• Detection of sodium in the atmosphere of WASP-69b
• Atmospheric dynamics and the variable transit of KELT-9 b
• The center-to-limb variation across the Fraunhofer lines of HD 189733; Sampling the stellar spectrum using a transiting planet
• Ground-based detection of Calcium and possibly Scandium and Hydrogen in the atmosphere of HD 209458b
• Searching for Thermal Inversion Agents in the Transmission Spectrum of MASCARA-2b/KELT-20b: Detection of Neutral Iron and Ionised Calcium H$\&$K Lines
• Optical hydrogen absorption consistent with a thin bow shock leading the hot Jupiter HD 189733b
• The atmosphere of HD 209458b seen with ESPRESSO. No detectable planetary absorptions at high resolution
• The Properties of the 500 K Dwarf UGPS J072227.51-054031.2, and a Study of the Far-Red Flux of Cold Brown Dwarfs
• Hydrogen and Sodium Absorption in the Optical Transmission Spectrum of WASP-12b
• Is there NaI in the atmosphere of HD 209458b? Effect of the centre-to-limb variation and Rossiter-McLaughlin effect in transmission spectroscopy studies
• Exonephology: Transmission spectra from a 3D simulated cloudy atmosphere of HD209458b
• Exoplanetary atmospheric sodium revealed by the orbital motion. Narrow-band transmission spectroscopy of HD 189733b with UVES
• The effects of stellar activity on optical high-resolution exoplanet transmission spectra
• A Model of the H$\alpha$ and Na Transmission Spectrum of HD 189733b
• CHEOPS geometric albedo of the hot Jupiter HD 209458b
• The Dawes Review 3: The Atmospheres of Extrasolar Planets and Brown Dwarfs
• Detection of sodium absorption in WASP-17b with Magellan
• GTC OSIRIS transiting exoplanet atmospheric survey: detection of potassium in HAT-P-1b from narrowband spectrophotometry
• Variation in the pre-transit Balmer line signal around the hot Jupiter HD 189733 b
• Characterizing exoplanetary atmospheres at high resolution with SPIRou: Detection of water on HD 189733 b
• Further constraints on the optical transmission spectrum of HAT-P-1b
• The potassium absorption on HD189733b and HD209458b
• How Much Information Does the Sodium Doublet Encode? Retrieval Analysis of Non-LTE Sodium Lines at Low and High Spectral Resolutions
• Assessing telluric correction methods for Na detections with high-resolution exoplanet transmission spectroscopy
• Modeling synthetic spectra for transiting extrasolar giant planets: detectability of H${}_2$S and PH${}_3$ with JWST
• Non-Local Thermodynamic Equilibrium Transmission Spectrum Modelling of HD209458b
• Probing the atmosphere of HD189733b with the Na I and K I lines
• Probing Na in giant exoplanets with ESPRESSO and 3D NLTE stellar spectra
• Illusion and Reality in the Atmospheres of Exoplanets
• The ESPRESSO transmission spectrum of HD189733b : Extracting the planetary sodium and lithium signatures amid stellar contamination
• A re-analysis of equilibrium chemistry in five hot Jupiters