Water observed in the atmosphere of τ Bootis Ab with CARMENES/CAHA

Abstract

Characterising the atmospheres of hot Jupiters is important in understanding the formation and migration of these exotic planets. However, there are still many open questions about the chemical and physical properties of these atmospheres. Here, we confirm the detection of water vapour in thermal emission from the non-transiting hot Jupiter τ Bootis Ab with the high resolution NIR CARMENES spectrograph. Combining over 17 h of observations (560 spectra) and using a Bayesian cross-correlation to log-likelihood approach, we measure a systemic velocity of $V_{sys}=-11.51_{-0.60}^{+0.59}$ km/s and a radial velocity semi-amplitude of $K_P=106.21_{-1.71}^{+1.76}$ km/s for the planet, which results in an absolute mass of $M_P=6.24_{-0.18}^{+0.17}{M}_J$ and an orbital inclination of $41.6_{-0.9}^{+1.0}$ degrees. Our retrieved $V_{sys}$ shows a significant shift (+5 km/s) from the literature value, which could be caused by an inaccurate time of periastron. Within the explored model grid, we measure a preference for solar water abundance (VMR = $10^{-3}$) and no evidence for additional minor species in the atmosphere. Given the extensive orbital coverage of the data, we searched for a phase dependency in the water signal but found no strong evidence of variation with orbital phase. This detection is at odds with recent observations from SPIRou/CFHT and their tight upper limit on water abundance. We recommend further observations of the atmosphere τ Bootis Ab to try and resolve these discrepancies.

Accepted for publication in MNRAS

References in corpus (23)

• Array Programming with NumPy
• Structure and Evolution of Nearby Stars with Planets II. Physical Properties of ~1000 Cool Stars from the SPOCS Catalog
• ExoMol molecular line lists XXXV: a rotation-vibration line list for hot ammonia
• Detection of Fe I in the atmosphere of the ultra-hot Jupiter WASP-121b, and a new likelihood-based approach for Doppler-resolved spectroscopy
• A solar C/O and sub-solar metallicity in a hot Jupiter atmosphere
• Five carbon- and nitrogen-bearing species in a hot giant planet's atmosphere
• Carbon monoxide and water vapor in the atmosphere of the non-transiting exoplanet HD 179949 b
• Spitzer Phase Curve Constraints for WASP-43b at 3.6 and 4.5 microns
• Weighing The Non-Transiting Hot Jupiter Tau BOO b
• Discovery of water at high spectral resolution in the atmosphere of 51 Peg b
• GENESIS: New Self-Consistent Models of Exoplanetary Spectra
• ExoMol molecular line lists -- XXXVII: spectra of acetylene
• Where is the Water? Jupiter-like C/H ratio but strong H${}_2$O depletion found on $\tau$ Boötis b using SPIRou
• The GAPS Programme with HARPS-N at TNG. VII. Putting exoplanets in the stellar context: magnetic activity and asteroseismology of $\tau$ Bootis A
• Confirmation of Asymmetric Iron Absorption in WASP-76b with HARPS
• Molecular Cross Sections for High Resolution Spectroscopy of Super Earths, Warm Neptunes and Hot Jupiters
• A Significant Increase in Detection of High-Resolution Emission Spectra Using a Three-Dimensional Atmospheric Model of a Hot Jupiter
• Detection of Fe\,{\sc i} Emission in the Day-side Spectrum of WASP-33b
• Seeing above the Clouds with High Resolution Spectroscopy
• Searching For Transiting Planets Around Halo Stars. II. Constraining the Occurrence Rate of Hot Jupiters
• Constraining the orbit of the planet-hosting binary $\tau$ Boötis: Clues about planetary formation and migration
• A search for He I airglow emission from the hot Jupiter tau Boo b
• The California Legacy Survey I. A Catalog of 178 Planets from Precision Radial Velocity Monitoring of 719 Nearby Stars over Three Decades

Cited by in corpus (2)

• How drifting and evaporating pebbles shape giant planets III: The formation of WASP-77A b and $\tau$ Boötis b
• The hot Neptune WASP-166 b with ESPRESSO III: A blue-shifted tentative water signal constrains the presence of clouds