Global Oscillations in Be Star Envelopes: Observational Evidence

Variability and pulsations in the Be star 66 Ophiuchi

“…Note that this distance agrees fairly well with d HIPP = 207 +40 −29 pc obtained from the parallax measured by the Hipparcos satellite. , Fontaine et al (1982), Lacy (1977), Hanuschik et al (1995), Hummel et al (1995), Peters (1987Peters ( , 1988aPeters ( ,b,c, 1989aPeters ( ,b, 1990Peters ( , 1991bPeters ( ,c, 1992Peters ( , 1994, Slettebak & Reynolds (1978) and this paper.…”

“…A minimun in Hα emission strength was observed around 1955 followed by the appearance of weak shell absorption at Hγ and Hδ in 1959. Hα emission EW changed steadily from ∼−23 Å in 1975 (Lacy 1977) to ∼−60 Å in 1993 (Hanuschik et al 1995). Emission level entered then a period of strong variability until 1995 during which its intensity oscillated around a high level (I/I c ∼ 9.2) (see Fig.…”

Long-term Variability in Be-Star disks

“…Nevertheless there are a few observations which might give useful insight. Hanuschik et al (1995) find that in 66 Oph the sudden onset of the V/R variations came after two decades of gradual increase of the emission line strength. By comparison, the onset of the current phase of V/R variations in 7 Cas came after decades of gradual visual brightening, i.e.…”

“…V/R cycle times range from less than two to more than ten years, and the same star can show different cycle times in its observational history. Mennickent et al (1997) present a list of observational facts such as: the cyclic timescale does not depend on v sin i or spectral type; the intensity of line emission does not correlate with V/R; the whole profile shifts redwards for V>R and vice-versa; in 7 Cas and 59 Cyg the discrete absorption components (DACs) in UV wind lines are stronger when V>R. Hanuschik et al (1995) list a few of the proposed models for long-term V/R variations: global one-armed oscillations (Okazaki 1991, Papaloizou et al 1992, Savonije & Heemskerk 1993, alternating spherical/ellipsoidal infall and outflow (cannot be the case: e.g. Telting et al 1993, Quirrenbach et al 1997, Wood et al 1997, and binarity (cannot be the case: e.g.…”

“…Hanuschik et al (1995) model Fell emission line profiles of 66 Oph and 8 Cen as a function of V/R phase, with a GOADO density and velocity perturbation superposed on a disk with a r~2 density law. Hummel k. Hanuschik (1997) use a 3D radiative transfer…”