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Astron. Astrophys. 324, 929-940


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Multi-site continuous spectroscopy

V. Rapid photospheric variability in the Be star 48 Persei
from the MUSICOS 1989 campaign*

A.M. Hubert1 and M. Floquet1, and J.X. Hao2, and S. Caillet1, and C. Catala3, and B.H. Foing4;5, and J.E. Neff6, and L. Huang2, and H. Hubert1,**, and C. Barban1, and J. Baudrand7, and H. Cao2, and S. Char5, and H. Chatzichristou1, and J.G. Cuby7, and J. Czarny7, and M. Dreux7, and P. Felenbok7, and J. Guérin7, and J. Hron8, and J. Huovelin9, and S. Jankov5, and S. Jiang2, and J.M. Le Contel10, and H.M. Maitzen8, and P. Petrov11, and I. Savanov11, and A. Shcherbakov11, and T. Simon12, and P. Stee10, and I. Tuominen9, and D. Zhai2

1DASGAL and Unité de Recherche Associée n FORMULA 335 du CNRS, Observatoire de Paris, Section de Meudon, F-92195 Meudon, France,
2Beijing Astronomical Observatory, China
3Observatoire Midi-Pyrénées
4ESA Solar System Division, Space Science Department, ESTEC (SO), The Netherlands
5Research Network in Space Science and Astrophysics (ICARUS), Europe and Institut d'Astrophysique Spatiale CNRS, France
6Penn State University, USA
7DAEC, Observatoire de Paris, Section de Meudon, France
8Vienna Observatory, Austria
9Helsinki Observatory, Finland
10Observatoire de la Côte d'Azur, France
11Crimea Astrophysical Observatory, CIS
12University of Hawaii, USA

Received 12 August 1996 / Accepted 18 October 1996

Abstract

Rapid variability in the photospheric He I 6678 line of the Be star 48 Per (HD 25940, HR 1273) has been detected from 258 high S/N CCD spectra taken with four 1.5-2.0 meter telescopes over three consecutive nights during the multi-site spectroscopic MUSICOS 1989 campaign. 48 Per is a rather moderate-V sin i star, known to have presented slight long-term variations in the intensity of Balmer emission lines and in the V/R ratio. It is shown that the MUSICOS 1989 observations preceded a new activity phase. Search for line-profile variations, hereafter lpv, was performed with time-series analysis using two methods (TF+CLEAN and Least-Squares) and with analysis of residuals. Weak blue-to-red and red-to-blue moving subfeatures with the same acceleration have been detected in the residuals. Their presence confirms that this star is seen under a moderate angle of inclination, FORMULA , in agreement with estimates based on fundamental stellar parameters. A 6.04 c/d frequency, associated with the moving subfeatures mentioned above, has been firmly established from time-series analysis and corresponds more closely, in the frame of non-radial pulsations (NRP), to a tesseral mode ( FORMULA ). Two other possible frequencies (0.85 and 2.77 c/d) have been detected but need to be confirmed with new observations obtained over a longer time span. Despite additional spectra obtained at Haute Provence Observatory, we could not confirm the previous value of the orbital period or the amplitude of the radial velocity curve of 48 Per, and therefore it was premature to search for tidally-forced oscillations.

Key words: lines: profiles - stars: emission-line, Be - stars: individual, 48 Per - stars: oscillations

Send offprint requests to: A.M. Hubert
* Based on observations obtained during the MUSICOS 1989 MUlti-SIte COntinuous Spectroscopic campaign from NSO McMath-Pierce, Univ. of Hawaii, Beijing Astronomical Observatory (BAO) and Xinglong Station, and Haute Provence Observatory telescopes
**Henri Hubert died on Feb. 10, 1996


© European Southern Observatory (ESO) 1997

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