TY - JOUR
T1 - A weak spectral signature of water vapour in the atmosphere of HD 179949 b at high spectral resolution in the L band
AU - Webb, Rebecca K.
AU - Brogi, Matteo
AU - Gandhi, Siddharth
AU - Line, Michael R.
AU - Birkby, Jayne L.
AU - Chubb, Katy L.
AU - Snellen, Ignas A.G.
AU - Yurchenko, Sergey N.
N1 - Publisher Copyright:
© 2020 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society
PY - 2020/5/1
Y1 - 2020/5/1
N2 - High-resolution spectroscopy (R ≽ 20 000) is currently the only known method to constrain the orbital solution and atmospheric properties of non-transiting hot Jupiters. It does so by resolving the spectral features of the planet into a forest of spectral lines and directly observing its Doppler shift while orbiting the host star. In this study, we analyse VLT/CRIRES (R = 100 000) L-band observations of the non-transiting giant planet HD 179949 b centred around 3.5 μm. We observe a weak (3.0σ, or S/N = 4.8) spectral signature of H2O in absorption contained within the radial velocity of the planet at superior-conjunction, with a mild dependence on the choice of line list used for the modelling. Combining this data with previous observations in the K band, we measure a detection significance of 8.4 σ for an atmosphere that is most consistent with a shallow lapse-rate, solar C/O ratio, and with CO and H2O being the only major sources of opacity in this wavelength range. As the two sets of data were taken 3 yr apart, this points to the absence of strong radial-velocity anomalies due, e.g. to variability in atmospheric circulation. We measure a projected orbital velocity for the planet of KP = (145.2 ± 2.0) km s−1 (1σ) and improve the error bars on this parameter by ∼70 per cent. However, we only marginally tighten constraints on orbital inclination (66.2+3.7-3.1 deg) and planet mass (0.963+0.0360.031 Jupiter masses), due to the dominant uncertainties of stellar mass and semimajor axis. Follow ups of radial-velocity planets are thus crucial to fully enable their accurate characterization via high-resolution spectroscopy.
AB - High-resolution spectroscopy (R ≽ 20 000) is currently the only known method to constrain the orbital solution and atmospheric properties of non-transiting hot Jupiters. It does so by resolving the spectral features of the planet into a forest of spectral lines and directly observing its Doppler shift while orbiting the host star. In this study, we analyse VLT/CRIRES (R = 100 000) L-band observations of the non-transiting giant planet HD 179949 b centred around 3.5 μm. We observe a weak (3.0σ, or S/N = 4.8) spectral signature of H2O in absorption contained within the radial velocity of the planet at superior-conjunction, with a mild dependence on the choice of line list used for the modelling. Combining this data with previous observations in the K band, we measure a detection significance of 8.4 σ for an atmosphere that is most consistent with a shallow lapse-rate, solar C/O ratio, and with CO and H2O being the only major sources of opacity in this wavelength range. As the two sets of data were taken 3 yr apart, this points to the absence of strong radial-velocity anomalies due, e.g. to variability in atmospheric circulation. We measure a projected orbital velocity for the planet of KP = (145.2 ± 2.0) km s−1 (1σ) and improve the error bars on this parameter by ∼70 per cent. However, we only marginally tighten constraints on orbital inclination (66.2+3.7-3.1 deg) and planet mass (0.963+0.0360.031 Jupiter masses), due to the dominant uncertainties of stellar mass and semimajor axis. Follow ups of radial-velocity planets are thus crucial to fully enable their accurate characterization via high-resolution spectroscopy.
KW - Planets
KW - Planets and satellites: atmospheres
KW - Planets and satellites: fundamental parameters
KW - Satellites: individual: HD 179949b
KW - Techniques: spectroscopic
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U2 - 10.1093/mnras/staa715
DO - 10.1093/mnras/staa715
M3 - Article
AN - SCOPUS:85085387027
SN - 0035-8711
VL - 494
SP - 108
EP - 119
JO - Monthly Notices of the Royal Astronomical Society
JF - Monthly Notices of the Royal Astronomical Society
IS - 1
ER -