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A photometric study of Be stars located in the seismology fields of COROT
Context: In preparation for the COROT mission, an exhaustive photometricstudy of Be stars located in the seismology fields of the mission hasbeen performed. The very precise and long-time-spanned photometricobservations gathered by the COROT satellite will give important clueson the origin of the Be phenomenon. Aims: The aim of this work is tofind short-period variable Be stars located in the seismology fields ofCOROT, and to study and characterise their pulsational properties. Methods: Light curves obtained at the Observatorio de Sierra Nevada,together with data from Hipparcos and ASAS-3 for a total of 84 Be stars,were analysed in order to search for short-term variations. We appliedstandard Fourier techniques and non-linear least-square fitting to thetime series. Results: We found 7 multiperiodic, 21 mono-periodic and 26non-variable Be stars. Short-term variability was detected in 74% ofearly-type Be stars and in 31% of mid- to late-type Be stars. We showthat non-radial pulsations are more frequent among Be stars than inslow-rotating B stars of the same spectral range.Appendix A is only available in electronic form at http://www.aanda.org
| Multiperiodic pulsations in the Be stars NW Serpentis and V1446 Aquilae
Aims:We present accurate photometric time series of two Be stars:NW Ser and V1446 Aql. Both starswere observed at the Observatorio de Sierra Nevada (Granada) in July2003 with an automatic four-channel Strömgren photometer. We alsopresent a preliminary theoretical study showing that the periodicvariations exhibited by these stars can be due to pulsation. Methods: An exhaustive Fourier analysis together with a least-squarefitting has been carried out on the time series for all fourStrömgren bands. Several independent frequencies and non-periodictrends explain most of the variance. A theoretical non-adiabatic codeapplied to stellar models for these stars shows that g-modes areunstable. Results: Both stars show rapid variations in amplitude,probably due to a beating phenomenon. Four significant frequencies havebeen detected for each star. Comparison of the observed amplitude ratiosfor each pulsational frequency with those calculated from theoreticalpulsation codes allows us to estimate the pulsation modes associatedwith the different detected frequencies. NW Ser seems also to showunstable p-modes and thus could be one of the newly discovered βCephei and SPB hybrid stars. Further spectroscopic observations areplanned to study the stability of the detected frequencies.Tables A.1 and A.2 are only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr(130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/472/565
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