Swift UVOT near-UV transit observations of WASP-121 b

Abstract

Close-in gas planets are subject to continuous photoevaporation that can erode their volatile envelopes. Today, ongoing mass loss has been confirmed in a few individual systems via transit observations in the ultraviolet spectral range. We demonstrate that the Ultraviolet/Optical Telescope (UVOT) onboard the Neil Gehrels Swift Observatory enables photometry to a relative accuracy of about 0.5% and present the first near-UV (200-270 nm, NUV) transit observations of WASP-121 b, a hot Jupiter with one of the highest predicted mass-loss rates. The data cover the orbital phases 0.85 to 1.15 with three visits. We measure a broad-band NUV transit depth of $2.10\pm 0.29$%. While still consistent with the optical value of 1.55%, the NUV data indicate excess absorption of 0.55% at a 1.9$\sigma$ level. Such excess absorption is known from the WASP-12 system, and both of these hot Jupiters are expected to undergo mass loss at extremely high rates. With a CLOUDY simulation, we show that absorption lines of Fe II in a dense extended atmosphere can cause broad-band NUV absorption at the 0.5% level. Given the numerous lines of low-ionization metals, the NUV range is a promising tracer of photoevaporation in the hottest gas planets.

7 pages, 6 figures, accepted for publication in A&A

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Cited by in corpus (31)

• Detection of Fe I in the atmosphere of the ultra-hot Jupiter WASP-121b, and a new likelihood-based approach for Doppler-resolved spectroscopy
• The HST PanCET Program: Exospheric Mg II and Fe II in the Near-UV transmission spectrum of WASP-121b using Jitter Decorrelation
• Hot Exoplanet Atmospheres Resolved with Transit Spectroscopy (HEARTS) IV. A spectral inventory of atoms and molecules in the high-resolution transmission spectrum of WASP-121 b
• Atmospheric Rossiter-McLaughlin effect and transmission spectroscopy of WASP-121b with ESPRESSO
• SO2, silicate clouds, but no CH4 detected in a warm Neptune
• Hot Exoplanet Atmospheres Resolved with Transit Spectroscopy (HEARTS) III. Atmospheric structure of the misaligned ultra-hot Jupiter WASP-121b
• Detection of neutral atomic species in the ultra-hot jupiter WASP-121b
• An emission spectrum for WASP-121b measured across the 0.8-1.1 micron wavelength range using the Hubble Space Telescope
• Non-detection of TiO and VO in the atmosphere of WASP-121b using high-resolution spectroscopy
• Detection of ionized calcium in the atmosphere of the ultra-hot Jupiter KELT-9b
• Optical phase curve of the ultra-hot Jupiter WASP-121b
• An inventory of atomic species in the atmosphere of WASP-121b using UVES high-resolution spectroscopy
• Non-local thermodynamic equilibrium effects determine the upper atmospheric temperature structure of the ultra-hot Jupiter KELT-9b
• Near-ultraviolet Transmission Spectroscopy of HD 209458b: Evidence of Ionized Iron Beyond the Planetary Roche Lobe
• Gemini/GMOS Optical Transmission Spectroscopy of WASP-121b: signs of variability in an ultra-hot Jupiter?
• High-resolution atmospheric retrievals of WASP-121b transmission spectroscopy with ESPRESSO: Consistent relative abundance constraints across multiple epochs and instruments
• UV Exoplanet Transmission Spectral Features as Probes of Metals and Rainout
• Exoplanet X-ray irradiation and evaporation rates with eROSITA
• A hydrodynamic study of the escape of metal species and excited hydrogen from the atmosphere of the hot Jupiter WASP-121b
• A large range of haziness conditions in hot-Jupiter atmospheres
• The secondary transit of the hot Jupiter WASP-121b at 2 $\mu$m
• Spitzer thermal phase curve of WASP-121 b
• Titanium chemistry of WASP-121 b with ESPRESSO in 4-UT mode
• Non-Local Thermodynamic Equilibrium Transmission Spectrum Modelling of HD209458b
• Searching for NLTE effects in the high-resolution transmission spectrum of WASP-121 b with Cloudy for Exoplanets
• Colorado Ultraviolet Transit Experiment Data Simulator
• Evidence of Titanate Clouds in the Day-side Atmosphere of the Ultra-Hot Jupiter WASP-121b
• Five new hot-Jupiter transits investigated with Swift-UVOT
• The near-UV transit of HD 189733b with the XMM-Newton Optical Monitor
• Impact of MgII interstellar medium absorption on near-ultraviolet exoplanet transit measurements
• Probing habitable regions with SRG/eROSITA