Properties and nature of Be stars
Astronomical Institute of the Charles University, Faculty of
Mathematics and Physics, V
Holešovičkách 2, 180
2 Astronomical Institute of the Academy of Sciences, 251 65 Ondřejov, Czech Republic
3 Department of Physics and Astronomy, University of North Carolina at Greensboro, Greensboro, NC 27402, USA
4 Physics & Astronomy Department, University of Victoria, PO Box 3055 STN CSC, Victoria, BC, V8W 3P6, Canada
5 Association des Utilisateurs de Détecteurs Électroniques (AUDE), 28 rue du Pic du Midi, 31130 Quint-Fonsegrives, France
Received: 20 August 2011
Accepted: 12 October 2011
A detailed analysis of more than 800 electronic high-resolution spectra of gamma Cas, which were obtained during a time interval of over 6000 days (16.84 yr) at several observatories, documents the smooth variations in the density and/or extent of its circumstellar envelope. We found a clear anticorrelation between the peak intensity and FWHM of the Hα emission, which seems to agree with recent models of such emission lines. The main result of this study is a confirmation of the binary nature of the object, determination of a reliable linear ephemeris and a rather definitive set of orbital elements. We clearly demonstrated that the orbit is circular within the limits of accuracy of our measurements and has a semi-amplitude of radial-velocity curve of 4.30 ± 0.09 km s-1. No trace of the low-mass secondary was found. The time distribution of our spectra does not allow a reliable investigation of rapid spectral variations, which are undoubtedly present in the spectra. We postpone this investigation for a future study, based on series of dedicated whole-night spectral observations.
Key words: binaries: spectroscopic / stars: early-type / stars: emission-line, Be
Based on new spectral and photometric observations from the Castanet-Tolosan, Dominion Astrophysical, Haute Provence, Hvar, Ondřejov, and Ritter Observatories.
Tables 2 and 3 are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (126.96.36.199) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/537/A59
Appendix A is available in electronic form at http://www.aanda.org
© ESO, 2012