TY - JOUR
T1 - Confirmation of water emission in the dayside spectrum of the ultrahot Jupiter WASP-121b
AU - Mikal-Evans, Thomas
AU - Sing, David K.
AU - Kataria, Tiffany
AU - Wakeford, Hannah R.
AU - Mayne, Nathan J.
AU - Lewis, Nikole K.
AU - Barstow, Joanna K.
AU - Spake, Jessica J.
PY - 2020/6/1
Y1 - 2020/6/1
N2 - We present four new secondary eclipse observations for the ultrahot
Jupiter WASP-121b acquired using the Hubble Space Telescope Wide Field
Camera 3. The eclipse depth is measured to a median precision of 60 ppm
across 28 spectroscopic channels spanning the 1.12- $1.64\, \mu \rm {m}$
wavelength range. This is a considerable improvement to the 90 ppm
precision we achieved previously for a single eclipse observation using
the same observing setup. Combining these data with those reported at
other wavelengths, a blackbody spectrum for WASP-121b is ruled out at
>6σ confidence and we confirm the interpretation of previous
retrieval analyses that found the data is best explained by a dayside
thermal inversion. The updated spectrum clearly resolves the water
emission band at 1.3- $1.6\, \mu \rm {m}$ , with higher signal-to-noise
than before. It also fails to reproduce a bump in the spectrum at
$1.25\, \mu \rm {m}$ derived from the first eclipse observation, which
had tentatively been attributed to VO emission. We conclude the latter
was either a statistical fluctuation or a systematic artefact specific
to the first eclipse dataset.
AB - We present four new secondary eclipse observations for the ultrahot
Jupiter WASP-121b acquired using the Hubble Space Telescope Wide Field
Camera 3. The eclipse depth is measured to a median precision of 60 ppm
across 28 spectroscopic channels spanning the 1.12- $1.64\, \mu \rm {m}$
wavelength range. This is a considerable improvement to the 90 ppm
precision we achieved previously for a single eclipse observation using
the same observing setup. Combining these data with those reported at
other wavelengths, a blackbody spectrum for WASP-121b is ruled out at
>6σ confidence and we confirm the interpretation of previous
retrieval analyses that found the data is best explained by a dayside
thermal inversion. The updated spectrum clearly resolves the water
emission band at 1.3- $1.6\, \mu \rm {m}$ , with higher signal-to-noise
than before. It also fails to reproduce a bump in the spectrum at
$1.25\, \mu \rm {m}$ derived from the first eclipse observation, which
had tentatively been attributed to VO emission. We conclude the latter
was either a statistical fluctuation or a systematic artefact specific
to the first eclipse dataset.
U2 - 10.1093/mnras/staa1628
DO - 10.1093/mnras/staa1628
M3 - Article (Academic Journal)
JO - Monthly Notices of the Royal Astronomical Society, Advance Access
JF - Monthly Notices of the Royal Astronomical Society, Advance Access
ER -