Mode identification and seismic study of $\delta$ Scuti, the prototype of a class of pulsating stars

Abstract

We present a seismic study of $\delta$ Scuti based on a mode identification from multicoulor photometry. The dominant frequency can be associated only with a radial mode and the second frequency is, most probably, a dipole mode. The other six frequencies have more ambiguous identifications. The photometric mode identification provided also some constraints on the atmospheric metallicity [m/H]$\approx$+0.5 and microturbulent velocity $ξ_t\approx 4~\kms$.\\ For models reproducing the dominant frequency, we show that only the fundamental mode is possible and the first overtone is excluded. However, the location of $\delta$ Scuti near the terminal age main sequence requires the consideration of three stages of stellar evolution. For the star to be on the main sequence, it is necessary to include overshooting from the convective core with a parameter of at least ${\alpha }_{\mathrm{ov}}=0.25$ at the metallicity greater than $Z=0.019$. It turned out that the value of the relative amplitude of the bolometric flux variations (the nonadiabatic parameter $f$) is mainly determined by the position of the star in the HR diagram, i.e., by its effective temperature and luminosity, whereas the effect of the evolutionary stage is minor. On the other hand, the convective efficiency in the subphotospheric layers has a dominant effect on the value of the parameter $f$. %in the $\delta$ Sct star models. Comparing the theoretical and empirical values of $f$ for the radial dominant mode, we obtain constraints on the mixing length parameter ${\alpha }_{\mathrm{MLT}}$ which is less than about 1.0, independently of the adopted opacity data and chemical mixture. This value of ${\alpha }_{\mathrm{MLT}}$ is substantially smaller than for a calibrated solar model indicating rather low to moderately efficient convection in the envelope of $\delta$ Scuti.

arXiv commentaccepted for publication in MNRAS, 17 pages, 13 figures, 3 tables

References in corpus (28)

• The chemical composition of the Sun
• Low Temperature Opacities
• The Geneva-Copenhagen Survey of the Solar neighbourhood III. Improved distances, ages, and kinematics
• On the use of empirical bolometric corrections for stars
• Stellar Turbulent Convection: A Selfconsistent Model
• A New Generation of Los Alamos Opacity Tables
• Hybrid gamma Doradus - delta Scuti pulsators: New insights into the physics of the oscillations from Kepler observations
• New grids of ATLAS9 atmospheres I: Influence of convection treatments on model structure and on observable quantities
• {\em Gaia}-derived luminosities of {\em Kepler} A/F stars and the pulsator fraction across the δ Scuti instability strip
• A new catalogue of Stroemgren-Crawford uvbybeta photometry
• Amplitude modulation in $\delta$ Sct stars: statistics from an ensemble study of Kepler targets
• Characterising the observational properties of δ Sct stars in the era of space photometry from the Kepler mission
• The first view of $\delta$ Scuti and $\gamma$ Doradus stars with the TESS mission
• Pulsation frequency distribution in Delta Scuti stars
• Automated spectroscopic abundances of A and F-type stars using echelle spectrographs II. Abundances of 140 A-F stars from ELODIE and CORALIE
• The Instability Strip for Pre--Main-Sequence Stars
• Detection of 75+ pulsation frequencies in the Delta Scuti star FG Vir
• OP data on CD for mean opacities and radiative accelerations
• SP_Ace: a new code to derive stellar parameters and elemental abundances
• Constraints on stellar convection from multi-colour photometry of Delta Scuti stars
• Echography of young stars reveals their evolution
• Inferences from pulsational amplitudes and phases for multimode $\delta$ Sct star FG Vir
• Interpretation of the BRITE oscillation data of the hybrid pulsator $\nu$ Eridani: a call for the modification of stellar opacities
• Amplitude variability or close frequencies in pulsating stars? The Delta Scuti star FG Vir
• Constraints on parameters of B-type pulsators from combined multicolour photometry and radial velocity data. I. $\beta$ Cephei stars
• Seismic modelling of early B-type pulsators observed by BRITE: I. $\theta$ Ophiuchi
• Seismic analysis of the double-mode radial pulsator SX Phoenicis
• Approaching asteroseismology of $\delta$ Scuti stars: problems and prospects

Cited by in corpus (5)

• Asteroseismology of the double-radial mode $\delta$ Scuti star BP Pegasi
• Unveiling $\delta$ Scuti and $\gamma$ Doradus Hybrid Pulsation of HD 53166 and HD 53349 Plus Rich Frequencies in HD 52788 -- Catalogs of 70552 $\delta$ Sct and 8080 $\gamma$ Dor
• A need to revise stellar opacities from asteroseismology of $\delta$ Scuti stars
• Asteroseismology of double-mode radial $\delta$ Scuti stars: AE Ursae Majoris and RV Arietis
• Asteroseismology