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Page Updated: Wed Jun 26 17:51:19 2019

Magnetic fields and activity in intermediate mass stars
after the red giant branch stage

Goals and Expected results

Magnetic field was detected in single late-type giant stars during the last decade. For this reason, the mechanisms for magnetic field generation and magnetic activity in giants is poorly studed, compared to those in dwarf stars on the main sequence. During the last years, we found that a significant percent of imtermediate mass M giants situated at the tip of the red giant branch (RGB) and at the asymptotic giant branch (AGB) possess magnetic fields of the order few G. For some of them Vsini is singificant greater than the predicted ones by the theory. The present project proposes a pilot study of the magnetic field variability in M giants and mapping of their surfce mаgntic fields after the rotation period is determined due to rotation modulation of the surface magnetic fields. We don't know if such magnetic maps exist for M giants and these ones will be performed for first time. Our sample contains 3 M giants with Vsini in the interval 7-10 km/s - RZ Ari, EK Boo and beta Peg. We have already spectropolrimetric data, but more data are necessary for their period determination and Zeeman Doppler Imiging (ZDI). For this purpose, we intend to pay for spectropolarimetric observations at 2m telescope with Narval, Pic du Midi Observtory, France. Quasi-simultaneous observations with the 60-cm telescop at AO-Belogradchik, Bulgaria will be carried out to follow the pulation phases (these giants are semi-regular pulating variable stars). The work team include researchers from Bulgaria and France. We have 2 young researchers and one PhD student in the Bulgarian part of the team. The results are expected to answer the next important questions: 1. What is the rotation period in the AGB stars? 2. Which mechanisms for magnetic field generation take part in these stars and how in the course of the stellar evolution and change of the internal structure the dynamo regime changes? 3. How the pulsations interact with the magnetic fields and how they contaminate the magnetic activity and dynamo operation in these evolved stars?
We expect this study to contribute to the global view of stellar magnetism in evolved stars - at which stages of the evolution we have magnetic activity, the mechanisms for magnetic field generation and their dependence on the change of the internal stellar structure, as a result of the stellar evolution.

The Team

The Team

  • Renada Konstantinova-Antova, Prof. Dr., Team Leader
  • Svetla Tsvetkova, Assoc.Prof. Dr., secretary
  • Rumen Bogdanovski, Dr.
  • Stefan Georgiev, PhD student
  • Ana Borisova, Assist. Prof. Dr. - deceased
  • Agnes Lebre, Prof. Dr. - LUPM, Univ. Montpellier, France
  • Ana Palacios, Dr. - LUPM, Univ. Montpellier, France
  • Eric Josselin, Dr. - OMP, Tarbes, France
The team
The team at the first workshop in Hisarrya, Bulgaria


Project DN 18/2 first workshop

First Workshop of the project DN 18/2 took place in Hissarya, Bulgaria from 15-17.04.2019. The work program and the list of participants can be found here:


Talks and Publications