March Monthly Meeting – Activity in the atmosphere of distant eclipsing binary star BF Velorum

Our meetings include brief business, a main presentation and items of astronomical news or learning from members.

The March Main Item will be: Chromospherical activity in BF Velorum and the effect of a third star in the system, by Dr David Moriarty (AAQ President).
Synopsis below.

The March 2023 meeting is planned to be a face-to-face meeting; attendees can also join in online via Zoom. Details emailed to members. Guests/visitors can contact us for Zoom details at .
Visitors are welcome to join our face-to-face or online meetings.

Synopsis – Chromospherical activity in BF Velorum and the effect of a third star in the system

The eclipsing binary BF Velorum was discovered in 1939, but was not studied in detail until 2006, when CCD light curves were observed by a group from the National Observatory of Athens, Greece, during a visit to the South African Astronomical Observatory. They discovered that its primary component pulsates and as this presented an opportunity to continue detailed study, BF Vel was added to David’s current research project.
Despite it being identified as an eclipsing binary, David’s spectra indicated that it was, in fact, a triple system. Using the sodium doublet lines to determine the primary star’s velocities is therefore challenging, as the lines of the primary star are partly blended with those of the third member of the system.
The principal components of BF Vel are both larger than the Sun, orbit their systemic centre of gravity in only 16.8 hours, and are only one solar diameter apart. Consequently, the magnetic activity is intense, and gives rise to activity in the chromosphere and emission in the Balmer lines, the sodium lines, and elsewhere.
In his presentation, David will describe the principal features of BF Velorum, the techniques he has used in its analysis, the issues presented by a third component, and the features of the observed chromospherical activity.