A full transit of ${\nu }^2$ Lupi d and the search for an exomoon in its Hill sphere with CHEOPS

Abstract

The planetary system around the naked-eye star ${\nu }^2$ Lupi (HD 136352; TOI-2011) is composed of three exoplanets with masses of 4.7, 11.2, and 8.6 Earth masses. The TESS and CHEOPS missions revealed that all three planets are transiting and have radii straddling the radius gap separating volatile-rich and volatile-poor super-earths. Only a partial transit of planet d had been covered so we re-observed an inferior conjunction of the long-period 8.6 Earth-mass exoplanet ${\nu }^2$ Lup d with the CHEOPS space telescope. We confirmed its transiting nature by covering its whole 9.1 h transit for the first time. We refined the planet transit ephemeris to P = 107.1361 (+0.0019/-0.0022) days and Tc = 2,459,009.7759 (+0.0101/-0.0096) BJD_TDB, improving by ~40 times on the previously reported transit timing uncertainty. This refined ephemeris will enable further follow-up of this outstanding long-period transiting planet to search for atmospheric signatures or explore the planet's Hill sphere in search for an exomoon. In fact, the CHEOPS observations also cover the transit of a large fraction of the planet's Hill sphere, which is as large as the Earth's, opening the tantalising possibility of catching transiting exomoons. We conducted a search for exomoon signals in this single-epoch light curve but found no conclusive photometric signature of additional transiting bodies larger than Mars. Yet, only a sustained follow-up of ${\nu }^2$ Lup d transits will warrant a comprehensive search for a moon around this outstanding exoplanet.

16 pages, 9 figures. Accepted for publication in Astronomy & Astrophysics

References in corpus (24)

• Gaia Early Data Release 3: Parallax bias versus magnitude, colour, and position
• Spectroscopic parameters for 451 stars in the HARPS GTO planet search program. Stellar [Fe/H] and the frequency of exo-Neptunes
• The CHEOPS mission
• CLES, Code Liegeois d'Evolution Stellaire
• The Mass of Kepler-93b and The Composition of Terrestrial Planets
• Revising the ages of planet-hosting stars
• Photoevaporation vs. core-powered mass-loss: model comparison with the 3D radius gap
• Determination of the size, mass, and density of "exomoons" from photometric transit timing variations
• Coreless Terrestrial Exoplanets
• A new class of Super-Earths formed from high-temperature condensates: HD219134 b, 55 Cnc e, WASP-47 e
• Transit detection of the long-period volatile-rich super-Earth ${\nu }^2$ Lupi d with $CHEOPS$
• CHEOPS observations of the HD 108236 planetary system: A fifth planet, improved ephemerides, and planetary radii
• Analysis of Early Science observations with the CHaracterising ExOPlanets Satellite (CHEOPS) using pycheops
• WASP-186 and WASP-187: two hot Jupiters discovered by SuperWASP and SOPHIE with additional observations by TESS
• A 20-Second Cadence View of Solar-Type Stars and Their Planets with TESS: Asteroseismology of Solar Analogs and a Re-characterization of pi Men c
• The atmosphere and architecture of WASP-189 b probed by its CHEOPS phase curve
• A pair of Sub-Neptunes transiting the bright K-dwarf TOI-1064 characterised with CHEOPS
• Reinvestigating $\alpha$ Cen AB in light of asteroseismic forward and inverse methods
• CHEOPS Precision Phase Curve of the Super-Earth 55 Cnc e
• CHEOPS geometric albedo of the hot Jupiter HD 209458b
• Improving exoplanet detection capabilities with the false inclusion probability. Comparison with other detection criteria in the context of radial velocities
• Transits of Known Planets Orbiting a Naked-Eye Star
• Pandora: A fast open-source exomoon transit detection algorithm
• Analytic Light Curve for Mutual Transits of Two Bodies Across a Limb-darkened Star

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• Unveiling the internal structure and formation history of the three planets transiting HIP 29442 (TOI-469) with CHEOPS
• The SOPHIE search for northern extrasolar planets-XIX. A system including a cold sub-Neptune potentially transiting a V = 6.5 star HD88986
• A review of planetary systems around HD 99492, HD 147379 and HD 190007 with HARPS-N
• The "Drake equation" of exomoons -- a cascade of formation, stability and detection
• Gas-depleted planet formation occurred in the four-planet system around the red dwarf LHS 1903
• The CHEOPS view of HD 95338b: refined transit parameters, and a search for exomoons