An asteroseismic study of the beta Cephei star 12 Lacertae: multisite spectroscopic observations, mode identification and seismic modelling

TL;DR

This study uses multisite spectroscopy over 11 months to identify pulsation modes and perform seismic modeling of the beta Cephei star 12 Lacertae, confirming known frequencies and constraining stellar parameters.

Contribution

It provides detailed mode identification and seismic modeling of 12 Lacertae using extensive multisite spectroscopic data, including detection of a g-mode and mode assignments.

Findings

Confirmed 10 independent frequencies including harmonics and combination frequencies.

Identified four main pulsation modes with specific spherical harmonic degrees and azimuthal orders.

Seismic modeling suggests the star's f2 mode is the radial first overtone and the core overshooting parameter is below 0.4.

Abstract

We present the results of a spectroscopic multisite campaign for the beta Cephei star 12 (DD) Lacertae. Our study is based on more than thousand high-resolution high S/N spectra gathered with 8 different telescopes in a time span of 11 months. In addition we make use of numerous archival spectroscopic measurements. We confirm 10 independent frequencies recently discovered from photometry, as well as harmonics and combination frequencies. In particular, the SPB-like g-mode with frequency 0.3428 1/d reported before is detected in our spectroscopy. We identify the four main modes as (l1,m1) = (1, 1), (l2,m2) = (0, 0), (l3,m3) = (1, 0) and (l4,m4) = (2, 1) for f1 = 5.178964 1/d, f2 = 5.334224 1/d, f3 = 5.066316 1/d and f4 = 5.490133 1/d, respectively. Our seismic modelling shows that f2 is likely the radial first overtone and that the core overshooting parameter alpha_ov is lower than 0.4 local pressure scale heights.