Recent re-determination of stellar atmospheric parameters for a sample of stars observed during the Kepler mission allowed to enlarge the number of Kepler B-type stars. We present the detailed frequency analysis for all these objects. All stars exhibit pulsational variability with maximum amplitudes at frequencies corresponding to high-order g modes. Peaks that could be identified with low-order p/g modes are also extracted for a few stars. We identified some patters in the oscillation spectra that can be associated with the period spacings that can results from the asymptotic nature of the detected pulsational modes. We also tentatively confront the observed oscillation characteristics with predictions from linear nonadiabatic computations of stellar pulsations. For high-order g modes the traditional approximation was employed to include the effects of rotation on the frequency values and mode instability.

The analysis of the BRITE oscillation spectrum of the main sequence early B-type star ν Eridani is presented. Only models with the modified mean opacity profile can account for the observed frequency ranges as well as for the values of some individual frequencies. The number of the κ modified seismic models is constrained by the nonadiabatic parameter f , which is very sensitive to the opacity changes in the subphotospheric layers where the pulsations are driven. We present an example of the model that satisfies all the above conditions. It seems that the OPLIB opacities are preferred over those from the OPAL and OP projects. Moreover, we discuss additional consequences of the opacity modification, namely, an enhancement of the efficiency of convection in the Z-bump as well as an occurrence of close radial modes which is a kind of avoided-crossing phenomenon common for nonradial modes in standard main sequence models.

Aims. Our goal is to test the newly developed OPLIB opacity tables from Los Alamos National Laboratory and check their influence on the pulsation properties of B-type stars. Methods. We calculated models using MESA and Dziembowski codes for stellar evolution and linear, nonadiabatic pulsations, respectively. We derived the instability domains of β Cephei and SPB-types for different opacity tables OPLIB, OP, and OPAL. Results. The new OPLIB opacities have the highest Rosseland mean opacity coefficient near the so-called Z-bump. Therefore, the OPLIB instability domains are wider than in the case of OP and OPAL data.

We undertake another attempt towards the seismic modelling of the most intensively studied main‐sequence early B spectral type pulsator, ν Eridani. Our analysis is extended by a requirement of fitting not only pulsational frequencies but also the complex amplitude of the bolometric flux variation, f, related to each mode frequency. This approach, termed complex asteroseismology, provides a unique test of stellar parameters, atmospheres and opacities. In particular, the concordance of the empirical and theoretical values of f we obtained for the high‐order g mode offers a new insight into seismic studies of main‐sequence hybrid pulsators. The most intriguing and challenging result is that, whereas an agreement of the theoretical and empirical values of f for the radial mode can be achieved only with the OPAL data, a preference for the OP tables is obtained from the analysis of the high‐order gravity mode.

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Abstract. The long-time photometric surveys in a few young open clusters allowed to identify the light variability in stars located on the HR diagram between the well defined δ Scuti variables and Slowly Pulsating B-type stars. Several objects of this type were suggested also from the analysis of the Kepler data. Assuming the pulsational origin of this variability, we try to explain the observed frequencies with pulsational models involving rotation and/or modification of the mean opacity profile.

Results of mode identification and seismic modelling of the β Cep/SBP star 12 Lacertae are presented. Using data on the multi-colour photometry and radial velocity variations, we determine or constrain the mode degree, ℓ, for all pulsational frequencies. Including the effects of rotation, we show that the dominant frequency, ν 1 , is most likely a pure ℓ = 1 mode and the low frequency, ν A , is a dipole retrograde mode. We construct a set of seismic models which fit two pulsational frequencies corresponding to the modes ℓ = 0, p 1 and ℓ = 1, g 1 and reproduce also the complex amplitude of the bolometric flux variations, f , for both frequencies simultaneously. Some of these seismic models reproduce also the frequency ν A , as a mode ℓ = 1, g 13 or g 14 , and its empirical values of f . Moreover, it was possible to find a model fitting the six 12 Lac frequencies (the first five and ν A ), only if the rotational splitting was calculated for a velocity of V rot ≈ 75 km/s. In the next step, we check the effects of model atmospheres, opacity data, chemical mixture and opacity enhancement. Our results show that the OP tables are preferred and an increase of opacities in the Z−bump spoils the concordance of the empirical and theoretical values of f .

We analyse TESS light curves for 70 southern λ Boo stars to identify binaries and to determine which of them pulsate as δ Scuti stars. We find two heartbeat stars and two eclipsing binaries among the sample. We calculate that 81 per cent of λ Boo stars pulsate as δ Sct variables, which is about twice that of normal stars over the same parameter space. We determine the temperatures and luminosities of the λ Boo stars from photometry and Gaia DR2 parallaxes. A subset of 40 λ Boo stars have 2-min TESS data, reliable temperatures and luminosities, and δ Sct pulsation. We use Petersen diagrams (period ratios), échelle diagrams, and the period–luminosity relation to identify the fundamental mode in 20 of those 40 stars and conclude that a further 8 stars are not pulsating in this mode. For the remaining 12, the fundamental mode cannot be unambiguously identified. Further mode identification is possible for 12 of the fundamental mode pulsators that have regular sequences of pulsation overtones in their échelle diagrams. We use stellar evolution models to determine statistically that the λ Boo stars are only superficially metal weak. Simple pulsation models also better fit the observations at a metallicity of Z = 0.01 than at Z = 0.001. The TESS observations reveal the great potential of asteroseismology on λ Boo stars, for determining precise stellar ages and shedding light on the origin(s) of the λ Boo phenomenon.