The periodic variations of a white-light flare observed with ULTRACAM
Abstract
High time resolution observations of a white-light flare on the active star EQ PegB show evidence of intensity variations with a period of ≈10 s. The period drifts to longer values during the decay phase of the flare. If the oscillation is interpreted as an impulsively-excited, standing-acoustic wave in a flare loop, the period implies a loop length of ≈3.4 Mm and ≈6.8 Mm for the case of the fundamental mode and the second harmonic, respectively. However, the small loop lengths imply a very high modulation depth making the acoustic interpretation unlikely. A more realistic interpretation may be that of a fast-MHD wave, with the modulation of the emission being due to the magnetic field. Alternatively, the variations could be due to a series of reconnection events. The periodic signature may then arise as a result of the lateral separation of individual flare loops or current sheets with oscillatory dynamics (i.e., periodic reconnection).
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- September 2006
- DOI:
- 10.1051/0004-6361:20054752
- arXiv:
- arXiv:astro-ph/0605196
- Bibcode:
- 2006A&A...456..323M
- Keywords:
-
- waves;
- stars: activity;
- stars: atmospheres;
- stars: flare;
- stars: individual: EQ Pegasi;
- Astrophysics
- E-Print:
- 10 pages, 3 figures, accepted for Astronomy Astrophysics