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Seismology of Stellar Coronal Flares
It was already known that stars of a similar spectral type as the Sun emit a significant amount of X-rays. This energetic radiation is emitted by the stellar corona. Often coronae undergo a major restructuring of the magnetic field: a solar or stellar flare that is a giant explosion of magnetic energy. It is well established that these flares often show periodicities in their light curve. This phenomenon is called “quasi-periodic pulsations (QPP)”. In solar physics, several groups are currently working on the seismology of the QPPs, i.e. they infer flare plasma properties (e.g. plasma-beta) by the study of the properties of the oscillations (e.g. period).
The aim of the workshop was to discuss possible science avenues in the seismology of oscillating light curves in stellar flares. This new branch of astrophysics could employ the expertise gained in the solar context and extend it to the stellar regime. A major restriction, however, is the loss of spatial resolution in the stellar coronal observations. Another aim of the workshop was to set up collaborations that enabled advances in the field.
To advance in the field of stellar coronal seismology, we invited experts in the field of solar coronal seismology and the field of stellar activity. Approximately half of the experts had a background in stellar observations of coronae and stellar activity. The other half had a history in the observation and physics of solar flares and/or solar coronal seismology. Our program planned scientific presentations in the morning, with discussions in the afternoon. However, in practice, we have taken extensive time after each presentation to discuss the content, how it related to other work, and what consequence it could have for stellar coronal seismology. One of the great successes of this workshop was indeed the lengthy discussions on each talk, because this working method resulted in a very close interaction between all participants and generated a great understanding between the two communities.
There are several scientific outcomes of the workshop. On the one hand, there is an article published in the Astrophysical Journal (The decaying long-period oscillation of a stellar megaflare by Anfinogentov S., Nakariakov V.M., Mathioudakis M., Van Doorsselaere T, and Kowalski A.F., 2013) of which the work was discussed at the Lorentz workshop@Snellius. On the other hand, we are aware of several collaborations that originated at the workshop. For instance, there is a collaboration between Armagh Observatory (UK) and KU Leuven (Belgium) to study fast flare oscillations that have been observed with Galex. We are considering seeking funding from the Leverhulme Trust in the UK to form an International Network that will work on this topic over the next three years. Furthermore, it was noted at the workshop that several Galex targets were in the Kepler field of view. This could potentially provide multi-wavelength observations of stellar flares. Several groups were interested in continuing this line of thought.
Overall, the workshop has been a great success. All scientists were very active, eager to comment and to start scientific discussions. Many scientists were somehow engaged and are now involved in follow-up studies. We do not think this could have been achieved in a regular conference format and we believe that the success is due to the Lorentz Center’s unique meeting format and meeting facilities.