Be stars are non-supergiant B-type stars whose spectra have, or had at some time, one or more Balmer lines in emission. The mystery of the "Be phenomenon" is that the emission, which is well understood to originate from a flattened circumstellar envelope or disk, can come and go episodically on time scales of days to decades. Limber Observatory - P.O. Box 63599 - Pipe Creek TX 78063 David McDavid
Artist rendering of a Be star similar to what 28 Tau may resemble. Credit StScI
28 Tau (Pleione) >>>>
This is the resulting spectral profile of the periastron passage of 28 Tau that occured between 4 Nov and 1 Dec 2019. The increase and decease of the red and blue components of the H alpha line is very obvious. This is an example of the data that is collected and submitted to various data bases for all to use.