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Ensemble Pulsational Characteristics of beta Cep pulsators in eclipsing binaries

Eze, Christian Ikechukwu

Abstract

Fast rotating massive pulsators in eclipsing binaries are ideal candidates for studying interior mixingand angular momentum transport in massive stars. Different mixing processes such as convectiveovershooting, which transports only matter, and convective penetration, which transports both matterand heat, occur at the boundary between the convective and the radiative layers in a massive star.These processes increase the core mass of the star and are also strongly affected by fast internalrotation. Fast internal rotation also diminishes the effect of tidal forces, often resulting in non-synchronous rotation, and causes rotational mode splitting, complicating mode identification. Thisstudy investigates the pulsational characteristics and their impact on the structure and evolution of fast-rotating β Cep pulsators in eclipsing binaries. Here, we analyse an ensemble of 73 such systems,identify rotationally split modes where possible, and statistically derive the dependence of pulsationalproperties on stellar and binary dynamical parameters. Interior properties of the systems were alsoderived using pre-computed grids of stellar structure models using MESA and associated pulsationfrequencies using GYRE. The rotational parameters are also derived for 15 systems exhibiting clearrotational mode spliting. The inferred properties provide new insights into the structure andevolutionary pathways of β Cep stars in binary systems.

Full text

Ensemble Pulsational Characteristics of β Cep pulsators in eclipsing binaries Christian Ikechukwu Eze PhD student, CAMK PAN, Warsaw, Poland TASC9/KASC16, July 10, 2025 Supervisor: Prof Gerald Handler Collaborators: C. Aerts, M. Vanrespaille, T. Pawar, A. Kemp, A. Tkachenko and D. Bowman Introduction ●Eclipsing binaries (EB: e.g. IJspeert et al. 2021) ●EB and bCEP (e.g. Eze and Handler, 2024) ●Ensemble asteroseismology of single bCEP (Fritzewski et al., 2025) 4.14.24.34.44.54.6 Log Teff 2.5 3.0 3.5 4.0 4.5 5.0 5.5 Log L/ L 4 M 5 M 6 M 8 M 10 M 12 M 15 M 20 M 25 M confirmed bCep in EB candidate bCep in EB bCep in ELL rejected targets Eze & Handler (2024), ApJS, 272:25 Distributions of pulsation frequencies and amplitudes Ground-based photometric mode Identification Pulsation amplitude dilution and correction sdss2010-u sdss2010-g sdss2010-r Filter 0.005 0.010 0.015 0.020 0.025 Amplitude Observed vs. Corrected Amplitudes for Multiple Frequencies f1(5.553420) Obs f1(5.553420) Intrinsic f2(5.666565) Obs f2(5.666565) Intrinsic Mode ID 350 400 450 500 550 600 650 700 750 wavelength (nm) 0.5 1.0 1.5 2.0 2.5 3.0 A_ratio f_obs=5.55342 c/d n=2, l=1, f_grid=5.3066 c/d n=2, l=2, f_grid=5.9932 c/d n=3, l=3, f_grid=5.104 c/d n=2, l=0, f_grid=6.1213 c/d Mode ID from rotational splitting Rotational Frequency Calculation: f_i = 6.825174, f_j = 7.526095, f_k = 8.228318 l_value = 2 Δ_ij = |f_i - f_j| = 0.700921 Δ_jk = |f_j - f_k| = 0.702223 Rotational Frequency = (0.700921 + 0.702223) / 4 = 0.35 8 Multivariate Linear regression analysis 9 Single variable linear regression analysis 0.5 0.6 0.7 0.8 0.9 1.0 1.1 LogF, d 1 1.0 0.5 0.0 0.5 1.0 LogA, mmag 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 LogP, d 1.0 0.5 0.0 0.5 1.0 LogA, mmag 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 LogP, d 0.6 0.8 1.0 LogF, d 1 r= -0.25, pvalue= 0.03