A study of bright southern slowly pulsating B stars* III. Mode identification for singly-periodic targets in spectroscopy

We present the results of the mode identification for a sample of 7 bright southern slowly pulsating B stars showing onepulsation frequency in the XX 413 nm Si II profiles. We combined the results from (1) the method of photometric amplitudes; (2) the moment method; and (3) the amplitude and phase variation across the profile to search for the l and m values of the modes best fitting the data. It is the first time that the applicability of these techniques is tested to a sample of main-sequence g-mode pulsators. Combining the moment method with the amplitude and phase variations across the observed line profile gives an improvement in spectroscopic identification of low degree I g-mode pulsations. Using the variations of the higher order even moments (v4> and (v6> of the moment method solutions can also help. For HD 181558, HD 24587, HD 140873 and HD 177863, the photometric and spectroscopic results are compatible and point towards (I, m) = (1, +1) sectoral modes. For HD 215573, HD 53921 and HD 92287, the results are inconclusive. Our proposed methodology for mode identification is also applicable to y Doradus stars.

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