The Directly-Imaged Exoplanet Host Star 51 Eridani is a Gamma Doradus Pulsator

Abstract

51 Eri is well known for hosting a directly-imaged giant planet and for its membership to the $\beta$ Pictoris moving group. Using two-minute cadence photometry from the Transiting Exoplanet Survey Satellite (TESS), we detect multi-periodic variability in 51 Eri that is consistent with pulsations of Gamma Doradus ($\gamma$ Dor) stars. We identify the most significant pulsation modes (with frequencies between $\sim$0.5-3.9 cycles/day and amplitudes ranging between $\sim$1-2 mmag) as dipole and quadrupole gravity-modes, as well as Rossby modes, as previously observed in Kepler $\gamma$ Dor stars. Our results demonstrate that previously reported variability attributed to stellar rotation is instead likely due to $\gamma$ Dor pulsations. Using the mean frequency of the $\ell =1$ gravity-modes, together with empirical trends of the Kepler $\gamma$ Dor population, we estimate a plausible stellar core rotation period of 0.9${}_{-0.1}^{+0.3}$ days for 51 Eri. We find no significant evidence for transiting companions around 51 Eri in the residual light curve. The detection of $\gamma$ Dor pulsations presented here, together with follow-up observations and modeling, may enable the determination of an asteroseismic age for this benchmark system. Future TESS observations would allow a constraint on the stellar core rotation rate, which in turn traces the surface rotation rate, and thus would help clarify whether or not the stellar equatorial plane and orbit of 51 Eri b are coplanar.

arXiv comment10 pages, 4 figures, 1 table. Accepted to ApJ after minor revisions. Abstract is unchanged. Figure 3 is corrected for extinction and reddening

References in corpus (65)

• SciPy 1.0--Fundamental Algorithms for Scientific Computing in Python
• Array Programming with NumPy
• Astropy: A Community Python Package for Astronomy
• The Astropy Project: Building an inclusive, open-science project and status of the v2.0 core package
• The Gaia mission
• The Transiting Exoplanet Survey Satellite
• Direct Imaging of Multiple Planets Orbiting the Star HR 8799
• The VizieR database of Astronomical Catalogues
• A 3D Dust Map Based on Gaia, Pan-STARRS 1 and 2MASS
• Kepler Presearch Data Conditioning II - A Bayesian Approach to Systematic Error Correction
• A box-fitting algorithm in the search for periodic transits
• Images of a fourth planet orbiting HR 8799
• Kepler Input Catalog: Photometric Calibration and Stellar Classification
• astroquery: An Astronomical Web-Querying Package in Python
• Kepler Presearch Data Conditioning I - Architecture and Algorithms for Error Correction in Kepler Light Curves
• The Hawaii Infrared Parallax Program. I. Ultracool Binaries and the L/T Transition
• Discovery and spectroscopy of the young Jovian planet 51 Eri b with the Gemini Planet Imager
• A self-consistent, absolute isochronal age scale for young moving groups in the solar neighbourhood
• On the Luminosity of Young Jupiters
• The Optical to Mid-Infrared Extinction Law Based on the APOGEE, Gaia DR2, Pan-STARRS1, SDSS, APASS, 2MASS and WISE Surveys
• Spectral and Photometric Diagnostics of Giant Planet Formation Scenarios
• On the age of the $\beta$ Pictoris moving group
• Bayesian analysis to identify new star candidates in nearby young stellar kinematic groups
• Rotational velocities of A-type stars. III. Velocity distributions
• Gamma Doradus Stars: Defining a New Class of Pulsating Variables
• The Hawaii Infrared Parallax Program. II. Young Ultracool Field Dwarfs
• Distances, Luminosities, and Temperatures of the Coldest Known Substellar Objects
• Hybrid gamma Doradus - delta Scuti pulsators: New insights into the physics of the oscillations from Kepler observations
• New Periodic Variables from the Hipparcos Epoch Photometry
• The interior rotation of a sample of gamma Doradus stars from ensemble modelling of their gravity mode period spacings
• Population-Level Eccentricity Distributions of Imaged Exoplanets and Brown Dwarf Companions: Dynamical Evidence for Distinct Formation Channels
• Meeting the Cool Neighbors VIII: A preliminary 20-parsec census from the NLTT catalogue
• SigSpec - I. Frequency- and Phase-Resolved Significance in Fourier Space
• {\em Gaia}-derived luminosities of {\em Kepler} A/F stars and the pulsator fraction across the δ Scuti instability strip
• Spectral and atmospheric characterization of 51 Eridani b using VLT/SPHERE
• Abundances in the Local Region II: F, G and K Dwarfs and Subgiants
• A novel L-band imaging search for giant planets in the Tucana and Beta Pictoris moving groups
• On the Inference of a Star's Inclination Angle from its Rotation Velocity and Projected Rotation Velocity
• Photometry and Proper Motions of M, L, and T Dwarfs from the Pan-STARRS1 3$\pi$ Survey
• A heuristic derivation of the uncertainty of the frequency determination in time series data
• Characterizing 51 Eri b from 1-5 $\mu$m: a partly-cloudy exoplanet
• The first view of $\delta$ Scuti and $\gamma$ Doradus stars with the TESS mission
• Dynamical traceback age of the $\beta$ Pictoris moving group
• A Volume-Limited Sample of Ultracool Dwarfs. I. Construction, Space Density, and a Gap in the L/T Transition
• Luminosity of young Jupiters revisited. Massive cores make hot planets
• Gas and dust in the Beta Pictoris Moving Group as seen by the Herschel Space Observatory
• Transiting exocomets detected in broadband light by TESS in the $\beta$ Pictoris system
• Astrometric Confirmation and Preliminary Orbital Parameters of the Young Exoplanet 51 Eridani b with the Gemini Planet Imager
• Improved Dynamical Masses for Six Brown Dwarf Companions Using Hipparcos and Gaia EDR3
• Evidence for granulation in early A-type stars
• Gravity-mode period spacings and near-core rotation rates of 611 $\gamma$ Doradus stars with \textit{Kepler}
• Age determination of the HR8799 planetary system using asteroseismology
• The SPHERE infrared survey for exoplanets (SHINE)- I Sample definition and target characterization
• Do A-type stars flare?
• 51 Eri and GJ 3305: A 10-15 Myr old binary star system at 30 parsecs
• Dynamical Masses of Young M Dwarfs: Masses and Orbital Parameters of GJ 3305 AB, the Wide Binary Companion to the Imaged Exoplanet Host 51 Eri
• Hint of curvature in the orbital motion of the exoplanet 51 Eridani b using 3 years of VLT/SPHERE monitoring
• Dynamical Mass of the Young Substellar Companion HD 984 B
• A $75\%$ Occurrence Rate of Debris Discs around F stars in the $\beta$ Pic Moving Group
• Limits on the Mass and Initial Entropy of 51 Eri b from Gaia EDR3 Astrometry
• An updated visual orbit of the directly-imaged exoplanet 51 Eridani b and prospects for a dynamical mass measurement with Gaia
• Measured Diameters of 2 F-stars in the Beta Pic Moving Group
• MOST light-curve analysis of the gamma Dor pulsator HR 8799, showing resonances and amplitude variations
• The near-core rotation of HD 112429: a gamma Doradus star with TESS photometry and legacy spectroscopy
• A search for transits among the δ Scuti variables in Kepler