Phase Changes in Be Stars: The Be-shell and Be phases of Pleione

Doazan, V.; Fuente, Anton de la; Cramer, N.; Barylak, M.

doi:10.1007/978-94-011-1030-3_98

Cited by 8 publications

(9 citation statements)

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“…On the one hand, only a few measurements have been published: e.g. Hα intensities of 4.3 on October 22, 1981 (Andrillat 1983) and 3.2 on February 6, 1986 (Doazan et al 1991) or Hβ profiles in 1966-67 (Kogure 1969. On the other hand, the "Un Atlas desétoiles Be" (Hubert & Hubert 1979) gives a summary of the monitoring, carried out from 1954 to 1975, of the level of the spectroscopic activity of OT Gem.…”

Section: Discussionmentioning

confidence: 99%

Monitoring the activity of the Be star OT Geminorum

Ferro

Sareyan

Avila

et al. 1998

Astron. Astrophys. Suppl. Ser.

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Abstract. Observations obtained in 1995-1996 of the Be star OT Geminorum are reported and show that in october 1995 the star reached a very active phase with large variations around a bright plateau, a phase of activity we have also distinguished in previous observations dating from 1960.The time scales involved are discussed and suggest that the violent variations of the activity propagate very quickly on the whole surface of the star or on a huge portion of it. No likely pulsation periods were found.The assumption that the detected activity is due to the effects of an hypothetical companion leads to conclude that such companion could not be detected by the present interferometric techniques.

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Section: Discussionmentioning

confidence: 99%

Monitoring the activity of the Be star OT Geminorum

Ferro

Sareyan

Avila

et al. 1998

Astron. Astrophys. Suppl. Ser.

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“…In addition, from 1978 to 1982, a new metallic shell phase was increasing, followed from 1983 to 1986 by a decreasing metallic shell and mild Be phase (Doazan et al 1982a;Hirata 1995). It was reported that the gradual weakening of Balmer emission and metallic shell lines in 1966-1970 was associated with brightening of the star (Doazan et al 1982b) and that a large and rapid drop of the luminosity occurred near 1978, just before the development (1978-1982) of a new Be-shell metallic phase (Harmanec et al 1980;Doazan et al 1986;Hirata 1995). The polarization percentage rapidly increased in 1978, followed by a slow decline from 1979 to 1985 (Arsenijević et al 1987).…”

Section: Lib (Hd 142983)mentioning

confidence: 99%

Long-term visual spectrophotometric behaviour of Be stars

Moujtahid

Zorec²,

Hubert

et al. 1998

Astron. Astrophys. Suppl. Ser.

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Abstract. The long-term spectrophotometric variations of 49 Be stars are studied using the U and V magnitudes of the UBV system, the total Balmer discontinuity D and the visible gradient Φ rb . BCD spectrophotometric and photometric data in five different photometric systems, obtained in most cases since 1950 and reduced to the BCD system, were used. The (U, D), (V, D), (Φ rb , D) and (Φ rb , V ) correlations obtained differ from star to star and they can be single or double-valued. They differ clearly for Be phases or Be-shell phases. Be stars with small V sin i showing the "spectrophotometric shell behaviour": D > D * , were found. This finding implies either that strongly flattened models of circumstellar envelopes are in doubt for these stars, or that not all Be stars are rapid rotators. Comparison of observed variations with those predicted for model Be stars with spherical circumstellar envelopes of variable densities and dimensions implies that spectrophotometric patterns of Be phases are due to circumstellar envelopes in low opacity regimes, while those of spectrophotometric shell phases are due to circumstellar envelopes in high opacity regimes. In a given star, the envelope regions responsible for the observed variations of D and Φ rb in spectrophotometric shell phases seem to be smaller and denser than those producing the observed variations of these parameters in spectrophotometric Be phases. The high positive RV found in strong shell phases might favor the formation of compact circumstellar layers near the star.

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“…Indeed, even at its present performance level, FLAGS does provide adequate resolving power and S/N ratio to detect fine structures like wine-bottle inflections in the profiles. As pointed out by Hanuschik (1996), these structures become apparent only when high resolution and S/N profiles are available (Hanuschik 1986(Hanuschik , 1987Hanuschik et al 1988;Doazan et al 1991;Slettebak et al 1992;Dachs et al 1992).…”

Section: Observationsmentioning

confidence: 99%