The planetary system host HR\,8799: On its $\lambda$ Bootis nature

Abstract

HR\,8799 is a $\lambda$ Bootis, $\gamma$ Doradus star hosting a planetary system and a debris disk with two rings. This makes this system a very interesting target for asteroseismic studies. This work is devoted to the determination of the internal metallicity of this star, linked with its $\lambda$ Bootis nature (i.e., solar surface abundances of light elements, and subsolar surface abundances of heavy elements), taking advantage of its $\gamma$ Doradus pulsations. This is the most accurate way to obtain this information, and this is the first time such a study is performed for a planetary-system-host star. We have used the equilibrium code CESAM and the non-adiabatic pulsational code GraCo. We have applied the Frequency Ratio Method (FRM) and the Time Dependent Convection theory (TDC) to estimate the mode identification, the Brunt-Vaïsälä frequency integral and the mode instability, making the selection of the possible models. When the non-seismological constraints (i.e its position in the HR diagram) are used, the solar abundance models are discarded. This result contradicts one of the main hypothesis for explaining the $\lambda$ Bootis nature, namely the accretion/diffusion of gas by a star with solar abundance. Therefore, according to these results, a revision of this hypothesis is needed. The inclusion of accurate internal chemical mixing processes seems to be necessary to explain the peculiar abundances observed in the surface of stars with internal subsolar metallicities. The use of the asteroseismological constraints, like those provided by the FRM or the instability analysis, provides a very accurate determination of the physical characteristics of HR 8799. However, a dependence of the results on the inclination angle $i$ still remains. The determination of this angle, more accurate multicolour photometric observations, and high resolution spectroscopy can definitively fix the mass and metallicity of this star.

11 pages, 10 figures. Accepted for publication in MNRAS

References in corpus (17)

• Direct Imaging of Multiple Planets Orbiting the Star HR 8799
• VOSA: Virtual Observatory SED Analyzer. An application to the Collinder 69 open cluster
• Chaotic star formation and the alignment of stellar rotation with disc and planetary orbital axes
• The Debris Disk Around HR 8799
• Probing the properties of convective cores through g modes: high-order g modes in SPB and gamma Doradus stars
• CESAM: a free code for stellar evolution calculations
• Diagnoses to unravel secular hydrodynamical processes in rotating main sequence stars
• A possible architecture of the planetary system HR 8799
• Solar System Analogs Around IRAS-Discovered Debris Disks
• The CoRoT Evolution and Seismic Tools Activity: Goals and Tasks
• Inter-comparison of the g-, f- and p-modes calculated using different oscillation codes for a given stellar model
• Granada oscillation Code (GraCo)
• The role of rotation on Petersen Diagrams. II The influence of near-degeneracy
• A comprehensive asteroseismic modelling of the high-amplitude delta Scuti star RV Arietis
• Long-term photometric monitoring with the Mercator telescope. Frequencies and multicolour amplitudes of $\gamma$ Doradus stars
• Asteroseismology with the WIRE satellite. I. Combining Ground- and Space-based Photometry of the Delta Scuti Star Epsilon Cephei
• Gravity modes in rapidly rotating polytropic stars

Cited by in corpus (17)

• Preparation of Kepler lightcurves for asteroseismic analyses
• Masses, Radii, and Cloud Properties of the HR 8799 Planets
• Near-Infrared Spectroscopy of the Extrasolar Planet HR 8799 b
• Constraining the initial entropy of directly-detected exoplanets
• The CHARA Array Angular Diameter of HR 8799 Favors Planetary Masses for Its Imaged Companions
• Observational Constraints on Companions inside of 10 AU in the HR 8799 Planetary System
• Could the planets around HR 8799 be brown dwarfs?
• Four-of-a-kind? Comprehensive atmospheric characterisation of the HR 8799 planets with VLTI/GRAVITY
• Asteroseismology of KIC 11754974: a high-amplitude SX Phe pulsator in a 343-day binary system
• On the Chemical Abundance of HR 8799 and the Planet c
• Dynamical Mass of the Exoplanet Host Star HR 8799
• Shaping HR8799's outer dust belt with an unseen planet
• IR-excesses around nearby Lambda Boo stars are caused by debris disks rather than ISM bow waves
• Clusters: age scales for stellar physics
• HD 54272, a classical lambda Bootis star and gamma Doradus pulsator
• Observational techniques to measure solar and stellar oscillations
• Pulsating stars harbouring planets