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.

10 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 (34)

• Array Programming with NumPy
• The Gaia mission
• The Transiting Exoplanet Survey Satellite
• Direct Imaging of Multiple Planets Orbiting the Star HR 8799
• astroquery: An Astronomical Web-Querying Package in Python
• 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
• On the age of the $\beta$ Pictoris moving group
• The Hawaii Infrared Parallax Program. II. Young Ultracool Field Dwarfs
• 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
• {\em Gaia}-derived luminosities of {\em Kepler} A/F stars and the pulsator fraction across the δ Scuti instability strip
• 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
• 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
• 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
• Improved Dynamical Masses for Six Brown Dwarf Companions Using Hipparcos and Gaia EDR3
• Gravity-mode period spacings and near-core rotation rates of 611 $\gamma$ Doradus stars with \textit{Kepler}
• The SPHERE infrared survey for exoplanets (SHINE)- I Sample definition and target characterization
• Do A-type stars flare?
• 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
• 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