Spectroscopy requested for the Be star BU Tau = Pleione
Abstract:
Spectroscopist Ernst Pollmann (Leverkusen, Germany) writes: For Be star observers: A rare event is imminent: The Hα spectrum of the Be star BU Tau (= 28 Tau = Pleione) will soon appear almost completely devoid of central shell absorption lines. This phenomenon is linked to the precession of the circumstellar disk, caused by the tidal torque of the companion star, which alters the disk inclination from a nearly edge-on to a nearly pole-on orientation by approximately i ≈ 30°. This change is reflected in variations of the Hα equivalent width (EW) and the central absorption features. The process recurs on a timescale of approximately 30 years.
Justification:
To study this rare event, spectra are urgently desired from now through July 2026. The campaign focuses exclusively on the Halpha emissions profile.
Requested Data Types:
Spectroscopy
Targets
| Name | Magnitude | Variability Type | Photometry Notes | Spectroscopy Notes |
|---|---|---|---|---|
| BU Tau | 4.83 | GCAS+LERI|SPB | Not Requested |
Cadence: Custom Resolution: 250 Desired SNR: 100 |
Spectroscopy Lines:
H-alpha (6563.0 Å)
Photometry Filters:
No photometry filters provided
Comparison Stars:
Finder charts with comparison stars for BU Tau may be created using the AAVSO Variable Star Plotter (VSP, https://apps.aavso.org/vsp/).
Co-Authorship
Observers are not eligible for co-authorship.
Additional Observer Input:
Spectra obtained at least nightly are requested to track the disappearance and re-appearance of the central shell absorption lines. As noted above, the campaign focuses exclusively on the Halpha emissions profile.
Additional Submission Location:
Not provided
Notes:
No public notes