HD207897 b: A dense sub-Neptune transiting a nearby and bright K-type star

Abstract

We present the discovery and characterization of a transiting sub-Neptune orbiting with a 16.20 day period around a nearby (28 pc) and bright(V=8.37) K0V star HD207897 (TOI-1611). This discovery is based on photometric measurements from the Transiting Exoplanet Survey Satellite(TESS) mission and radial velocity (RV) observations from the SOPHIE, Automated Planet Finder (APF) and HIRES high precision spectrographs. We used EXOFASTv2 for simultaneously modeling the parameters of the planet and its host star, combining photometric and RV data to determine the planetary system parameters. We show that the planet has a radius of 2.50+/-0.08 RE and a mass of either 14.4+/-1.6 ME or 15.9+/-1.6 ME with nearly equal probability; the two solutions correspond to two possibilities for the stellar activity period. Hence, the density is either 5.1+/-0.7 g cm^-3 or 5.5^{+0.8}_{-0.7} g cm^-3, making it one of the relatively rare dense sub-Neptunes. The existence of such a dense planet at only 0.12 AU from its host star is unusual in the currently observed sub-Neptune (2<RE<4) population. The most likely scenario is that this planet has migrated to its current position.

18 pages, 12 figures, 6 tables; accepted for publication in the A&A journal; comments welcome

References in corpus (33)

• The James Webb Space Telescope
• Improved Age Estimation for Solar-Type Dwarfs Using Activity-Rotation Diagnostics
• Most 1.6 Earth-Radius Planets are not Rocky
• EXOFAST: A fast exoplanetary fitting suite in IDL
• Planets and Stellar Activity: Hide and Seek in the CoRoT-7 system
• Spectrum radial velocity analyser (SERVAL). High-precision radial velocities and two alternative spectral indicators
• Measuring the rotation period distribution of field M-dwarfs with Kepler
• Accurate, Empirical Radii and Masses of Planets and their Host Stars with Gaia Parallaxes
• Assessing statistical significance of periodogram peaks
• Can we constrain interior structure of rocky exoplanets from mass and radius measurements?
• Three regimes of extrasolar planets inferred from host star metallicities
• Parallax Systematics and Photocenter Motions of Benchmark Eclipsing Binaries in Gaia EDR3
• 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
• Chemical abundances of 1111 FGK stars from the HARPS GTO planet search program II: Cu, Zn, Sr, Y, Zr, Ba, Ce, Nd and Eu
• Eclipsing Binary Stars as Benchmarks for Trigonometric Parallaxes in the Gaia Era
• SOPHIE velocimetry of Kepler transit candidates VII. A false-positive rate of 35% for Kepler close-in giant exoplanet candidates
• Empirical, Accurate Masses and Radii of Single Stars with TESS and Gaia
• The Kepler-10 planetary system revisited by HARPS-N: A hot rocky world and a solid Neptune-mass planet
• Formation of close in Super-Earths \& Mini-Neptunes: Required Disk Masses \& Their Implications
• High-resolution imaging of $Kepler$ planet host candidates. A comprehensive comparison of different techniques
• EXOFASTv2: A public, generalized, publication-quality exoplanet modeling code
• Oxygen abundances in G- and F-type stars from HARPS
• Radial Velocity Data Analysis with Compressed Sensing Techniques
• Constraints on Super-Earths Interiors from Stellar Abundances
• TESS delivers its first Earth-sized planet and a warm sub-Neptune
• Three Super-Earths Orbiting HD 7924
• Kepler-411: a four-planet system with an active host star
• Characterisation of the hydrospheres of TRAPPIST-1 planets
• Mass determinations of the three mini-Neptunes transiting TOI-125
• Systematics-insensitive Periodogram for finding periods in TESS observations of long-period rotators
• Testing whether a signal is strictly periodic. Application to disentangling planets and stellar activity in radial velocities
• Detection and characterization of an ultra-dense sub-Neptune planet orbiting the Sun-like star HD 119130

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• The SOPHIE search for northern extrasolar planets-XIX. A system including a cold sub-Neptune potentially transiting a V = 6.5 star HD88986
• Exoplanet atmosphere evolution: emulation with neural networks
• The AstraLux-TESS high-spatial resolution imaging survey. Search for stellar companions of 215 planet candidates from TESS
• TOI-1736 and TOI-2141: two systems including sub-Neptunes around solar analogs revealed by TESS and SOPHIE
• Characterization of seven transiting systems including four warm Jupiters from SOPHIE and TESS
• Chasing extreme planetary architectures: I- HD196885Ab, a super-Jupiter dancing with two stars?
• Chromaticity of stellar activity in radial velocities : Anti-correlated families of lines on the M dwarf EV Lac with SPIRou and SOPHIE
• TOI-1199 b and TOI-1273 b: Two new transiting hot Saturns detected and characterized with SOPHIE and TESS
• A homogeneous TTV investigation of all TESS systems with a confirmed single transiting planet
• Near-IR and optical radial velocities of the active M dwarf star Gl 388 (AD Leo) with SPIRou at CFHT and SOPHIE at OHP: A 2.23 day rotation period and no evidence for a corotating planet