Communications in Asteroseismology, Vol. 162 (September 2011)

Crawford’s uvby ß calibration method is examined for A-type stars by comparing it with the pulsational variations of the observable m1, c1 and MV for the δ Scuti star FG Vir. The fit between the calibration values of m1 and MV and the respective measurements for FG Vir are tested as a function of temperature based on 3068 4-colour values taken at the Observatorio de Sierra Nevada in Spain during the years 2002 and 2003. Testing is performed by means of linear regression. The fit between the measured index m1 of FG Vir and the m1 index of the Hyades is nearly perfect. A fit between the calibration value MV and the measured values of FG Vir cannot be obtained with Crawford’s calibration procedure in a straightforward manner. In order to achieve an optimal fit for MV two modifications of the calibration procedure are investigated and discussed. (i) the position of the ZAMS given by Crawford is replaced by the position of the ZAMS given by Mermilliod; (ii) the influence of the mass difference on c1 is taken into account.

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The recent detection of both pressure and high-order gravity modes in the classical B-type pulsator Pegasi offers promising prospects for probing its internal structure through seismic studies. To aid further modelling of this star, we present the results of a detailed NLTE abundance analysis based on a large number of time-resolved, high-quality spectra. A chemical composition typical of nearby B-type stars is found. The hybrid nature of this star is consistent with its location in the overlapping region of the instability strips for ß Cephei and slowly pulsating B stars computed using OP opacity tables, although OPAL calculations may also be compatible with the observations once the uncertainties in the stellar parameters and the current limitations of the stability calculations are taken into account. The two known frequencies f1 = 6.58974 and f2 = 0.68241 d-1 are detected in the spectroscopic time series. A mode identification is attempted for the low-frequency signal, which can be associated to a high-order g-mode. Finally, we re-assess the binary status of γ Peg and find no evidence for variations that can be ascribed to orbital motion, contrary to previous claims in the literature.

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CCD observations of five newly discovered pulsating stars are analyzed using the Period04 software for a comprehensive investigation of their pulsation properties. The type of their variability is discussed, and the pulsation frequencies and Fourier spectra are presented.

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Breger et al. (2011) reported on the discovery of 76 frequencies for the star KIC 9700322 from one month (Sept.-Oct. 2009) of short-cadence (1-minute sampling rate) photometric data during Quarter 3 of the NASA Kepler mission. Here we report on a reanalysis combining an additional month (June-July 2009) obtained during Quarter 2 as part of the Kepler Guest Observer program. This analysis confirms all but two of the earlier frequencies > 0.5 c/d, and in addition finds six new combination frequencies of the 8 highest amplitude modes, and three frequencies that are not combinations of these modes. Since we do not know the parents of 12 of the 83 frequencies, additional astrophysical discoveries may await in continued study of this star. The rotational modulations of the two radial modes and the 𝓁 = 2 quintuplet are confirmed. For the two radial modes (f1, f2) and the central (m = 0) mode of the 𝓁 = 2 quintuplet, f6, amplitude variability and/or close frequencies were found. The additional data do not reveal more of the 𝓁=0, 1, 2 or higher-degree p modes that were expected, and this result is still a mystery.

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New BVRI light curves of the eclipsing binary BG Peg were obtained and analysed using the Wilson-Devinney code. The observations (102 hours during a span of 108 days) were collected to perform an accurate frequency analysis of the pulsations of the primary component of the system, which is of δ Sct type. Three pulsation frequencies were identified in that star.

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