Characterization of the HD 108236 system with CHEOPS and TESS. Confirmation of a fifth transiting planet

Abstract

The HD108236 system was first announced with the detection of four small planets based on TESS data. Shortly after, the transit of an additional planet with a period of 29.54d was serendipitously detected by CHEOPS. In this way, HD108236 (V=9.2) became one of the brightest stars known to host five small transiting planets (R${}_p$<3R${}_{\oplus }$). We characterize the planetary system by using all the data available from CHEOPS and TESS space missions. We use the flexible pointing capabilities of CHEOPS to follow up the transits of all the planets in the system, including the fifth transiting body. After updating the host star parameters by using the results from Gaia eDR3, we analyzed 16 and 43 transits observed by CHEOPS and TESS, respectively, to derive the planets physical and orbital parameters. We carried out a timing analysis of the transits of each of the planets of HD108236 to search for the presence of transit timing variations. We derived improved values for the radius and mass of the host star (R${}_{\star }$=0.876$\pm$0.007 R${}_{\odot }$ and M${}_{\star }$=0.867${}_{-0.046}^{+0.047}$ M${}_{\odot }$). We confirm the presence of the fifth transiting planet f in a 29.54d orbit. Thus, the system consists of five planets of R${}_b$=1.587$\pm$0.028, R${}_c$=2.122$\pm$0.025, R${}_d$=2.629$\pm$0.031, R${}_e$=3.008$\pm$0.032, and R${}_f$=1.89$\pm$0.04 [R${}_{\oplus }$]. We refine the transit ephemeris for each planet and find no significant transit timing variations for planets c, d, and e. For planets b and f, instead, we measure significant deviations on their transit times (up to 22 and 28 min, respectively) with a non-negligible dispersion of 9.6 and 12.6 min in their time residuals. We confirm the presence of planet f and find no significant evidence for a potential transiting planet in a 10.9d orbital period, as previously suggested. Full abstract in the PDF file.

18 Figures and 25 pages. Accepted for publication in A&A

References in corpus (32)

• Array Programming with NumPy
• The James Webb Space Telescope
• The K2 Mission: Characterization and Early results
• Seven temperate terrestrial planets around the nearby ultracool dwarf star TRAPPIST-1
• Gaia Early Data Release 3: Parallax bias versus magnitude, colour, and position
• DHP Framework: Digital Health Passports Using Blockchain -- Use case on international tourism during the COVID-19 pandemic
• EXOFAST: A fast exoplanetary fitting suite in IDL
• The TESS Objects of Interest Catalog from the TESS Prime Mission
• The CHEOPS mission
• CLES, Code Liegeois d'Evolution Stellaire
• Transit Least Squares: Optimized transit detection algorithm to search for periodic transits of small planets
• Revisited Mass-Radius relations for exoplanets below 120 Earth masses
• A resonant chain of four transiting, sub-Neptune planets
• An ancient extrasolar system with five sub-Earth-size planets
• TTVFast: An efficient and accurate code for transit timing inversion problems
• Four newborn planets transiting the young solar analog V1298 Tau
• Revising the ages of planet-hosting stars
• The hot dayside and asymmetric transit of WASP-189b seen by CHEOPS
• Two massive rocky planets transiting a K-dwarf 6.5 parsecs away
• Constraints on Super-Earths Interiors from Stellar Abundances
• 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
• Characterisation of the hydrospheres of TRAPPIST-1 planets
• 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
• Analytical model of multi-planetary resonant chains and constraints on migration scenarios
• The Magellan-TESS Survey I: Survey Description and Mid-Survey Results
• Investigating the architecture and internal structure of the TOI-561 system planets with CHEOPS, HARPS-N and TESS
• Improving exoplanet detection capabilities with the false inclusion probability. Comparison with other detection criteria in the context of radial velocities
• Alleviating the transit timing variation bias in transit surveys. I. RIVERS: Method and detection of a pair of resonant super-Earths around Kepler-1705
• TESS discovery of a super-Earth and three sub-Neptunes hosted by the bright, Sun-like star HD 108236
• Water content trends in K2-138 and other low-mass multiplanetary systems

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