WASP-121 b: a hot Jupiter close to tidal disruption transiting an active F star

Delrez, Laetitia; Santerne, A.; Almenara, J. M.; Anderson, D. R.; Cameron, A. Collier; Díaz, R. F.; Gillon, M.; Hellier, C.; Jehin, Emmanuël; Lendl, M.; Maxted, P. F. L.; Neveu-VanMalle, M.; Pepe, F.; Pollacco, D.; Queloz, D.; Ségransan, D.; Smalley, B.; Smith, A. M. S.; Triaud, A. H. M. J.; Udry, S.; Grootel, Valérie Van; West, R. G.

doi:10.1093/mnras/stw522

Cited by 167 publications

(265 citation statements)

References 129 publications

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“…where we assume H(λ) << R * (an atmosphere generally extends 5-10 scale heights, or several thousand kilometers for a hot-Jupiter) (Madhusudhan et al 2014a). Using the ephemeris of Delrez et al (2016) (Table 2), we identify 13, 18, and 18 in-transit exposures for Nights 1, 2 and 3 respectively. We denote in-transit and out-of-transit spectra as f (λ, t in ), and f (λ, t out ).…”

Section: Transmission Spectramentioning

confidence: 99%

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Detection of neutral atomic species in the ultra-hot Jupiter WASP-121b

Cabot

Madhusudhan

Welbanks

et al. 2020

Monthly Notices of the Royal Astronomical Society

102

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The class of ultra-hot Jupiters comprises giant exoplanets undergoing intense irradiation from their host stars. They have proved to be a particularly interesting population for their orbital and atmospheric properties. One such planet, WASP-121 b, is in a highly misaligned orbit close to its Roche limit, and its atmosphere exhibits a thermal inversion. These properties make WASP-121 b an interesting target for additional atmospheric characterization. In this paper, we present analysis of archival high-resolution optical spectra obtained during transits of WASP-121 b. Artifacts from the Rossiter-McLaughlin effect and Center-to-Limb Variation are deemed negligible. However, we discuss scenarios where these effects warrant more careful treatment by modeling the WASP-121 system and varying its properties. We report a new detection of atmospheric absorption from Hα in the planet with a transit depth of 1.87 ± 0.11%. We further confirm a previous detection of the Na I doublet, and report a new detection of Fe I via cross-correlation with a model template. We attribute the Hα absorption to an extended Hydrogen atmosphere, potentially undergoing escape, and the Fe I to equilibrium chemistry at the planetary photosphere. These detections help to constrain the composition and chemical processes in the atmosphere of WASP-121 b.

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Section: Transmission Spectramentioning

confidence: 99%

“…It's semi-major axis is only ∼ 1.15 times its Roche limit, suggesting the planet is on the verge of tidal disruption. Deformation models suggest the planet may have radius R sub ∼ 2R jup at its sub-stellar point (Delrez et al 2016). The bright host star and extended atmosphere makes the planet a prime target for characterization.…”

Section: Introductionmentioning

confidence: 99%

Detection of neutral atomic species in the ultra-hot Jupiter WASP-121b

Cabot

Madhusudhan

Welbanks

et al. 2020

Monthly Notices of the Royal Astronomical Society

102

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“…Given the stellar radius of 1.69 R and an inclination of 90 • , the transit is expected to have a depth in the range 600-1200 ppm. For the most favourable case, this signal could be detected from the ground (Delrez et al 2016). It would otherwise be an easy case for space-based photometry with a dedicated observatory such as CHEOPS (Fortier et al 2014) or TESS (Ricker et al 2010).…”

Section: A System Full Of Potentialmentioning

confidence: 99%

An extreme planetary system around HD 219828

Santos

Santerne

Faria

et al. 2016

A&A

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Context. With about 2000 extrasolar planets confirmed, the results show that planetary systems have a whole range of unexpected properties. This wide diversity provides fundamental clues to the processes of planet formation and evolution. Aims. We present a full investigation of the HD 219828 system, a bright metal-rich star for which a hot Neptune has previously been detected. Methods. We used a set of HARPS, SOPHIE, and ELODIE radial velocities to search for the existence of orbiting companions to HD 219828. The spectra were used to characterise the star and its chemical abundances, as well as to check for spurious, activity induced signals. A dynamical analysis is also performed to study the stability of the system and to constrain the orbital parameters and planet masses. Results. We announce the discovery of a long period (P = 13.1 yr) massive (m sin i = 15.1 M Jup ) companion (HD 219828 c) in a very eccentric orbit (e = 0.81). The same data confirms the existence of a hot Neptune, HD 219828 b, with a minimum mass of 21 M ⊕ and a period of 3.83 days. The dynamical analysis shows that the system is stable, and that the equilibrium eccentricity of planet b is close to zero. Conclusions. The HD 219828 system is extreme and unique in several aspects. First, ammong all known exoplanet systems it presents an unusually high mass ratio. We also show that systems like HD 219828, with a hot Neptune and a long-period massive companion are more frequent than similar systems with a hot Jupiter instead. This suggests that the formation of hot Neptunes follows a different path than the formation of their hot jovian counterparts. The high mass, long period, and eccentricity of HD 219828 c also make it a good target for Gaia astrometry as well as a potential target for atmospheric characterisation, using direct imaging or high-resolution spectroscopy. Astrometric observations will allow us to derive its real mass and orbital configuration. If a transit of HD 219828 b is detected, we will be able to fully characterise the system, including the relative orbital inclinations. With a clearly known mass, HD 219828 c may become a benchmark object for the range in between giant planets and brown dwarfs.

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“…where q is the ratio between the stellar and planetary masses, F p is the ratio between the orbital and rotational periods, Θ is the obliquity. We assume a circular orbit (Delrez et al 2016) (d is equal to the semi-major axis), a synchronized rotation (F p = 1), and a rotational axis perpendicular to the orbital plane (Θ = θ).…”

Section: Transit Modelmentioning

confidence: 99%

HST/STIS Capability for Love Number Measurement of WASP-121b

Hellard

Csizmadia

Padovan

et al. 2020

ApJ

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Data from transit light curves, radial velocity and transit timing observations can be used to probe the interiors of exoplanets beyond the mean density, by measuring the Love numbers h 2 and k 2 . The first indirect estimate of k 2 for an exoplanet from radial velocity and transit timing variations observations has been performed by taking advantage of the years-spanning baseline. Not a single measurement of h 2 has been achieved from transit light curves, mostly because the photometric precision of current observing facilities is still too low. We show that the Imaging Spectrograph instrument on-board the Hubble Space Telescope could measure h 2 of the hot Jupiter WASP-121b if only few more observations were gathered. We show that a careful treatment of the noise and stellar limb darkening must be carried out to achieve a measurement of h 2 . In particular, we find that the impact of the noise modelling on the estimation of h 2 is stronger than the impact of the limb darkening modelling. In addition, we emphasize that the wavelet method for correlated noise analysis can mask limb brightening. Finally, using presently available data, we briefly discuss the tentative measurement of h 2 = 1.39 +0.71 −0.81 in terms of interior structure. Additional observations would further constrain the interior of WASP-121b and possibly provide insights on the physics of inflation. The possibility of using the approach presented here with the Hubble Space Telescope provides a bridge before the high-quality data to be returned by the James Webb Space Telescope and PLATO telescope in the coming decade.

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WASP-121 b: a hot Jupiter close to tidal disruption transiting an active F star

Cited by 167 publications

References 129 publications

Detection of neutral atomic species in the ultra-hot Jupiter WASP-121b

Detection of neutral atomic species in the ultra-hot Jupiter WASP-121b

An extreme planetary system around HD 219828

HST/STIS Capability for Love Number Measurement of WASP-121b

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