Dear colleagues,
our current monitoring of the Be star 28 Tau includes among others the observation of the depth of the central absorption (CA) in the Halpha emission (see attached Fig.). This CA reflects the disk inclination in the observers view.
The strong periodicity of the max. value of CA with its binary period of 218 days confirms each time the periastron passage of the compagnion star and hence the binary character of 28 Tau.
After the last periastron in our monitoring (JD 2459468) appears now an unexpected increase of CA, which feed the suspect, that there is a second companion star of the system.
Katahira, et al. (1996, PASJ, 48, 317), and Roberts et al. (The Astronomical Journal, 133, 2007 February) reports about signs of a possibility of a third body within their observations.
Possibly our unexpected observed increase of CA after the primary periastron might be in that sense an additional confirmation.
Please try to take spectra of 28 Tau as long as it posible for you.
Tue, 02/22/2022 - 18:52
Hello.
I am just now acquiring spectra.
How many spectra per night? Is low resolution acceptable?
David Cejudo
... once per week might be enough.
Ernst