EDP Sciences
Free Access
Issue
A&A
Volume 456, Number 1, September II 2006
Page(s) 323 - 327
Section Stellar atmospheres
DOI https://doi.org/10.1051/0004-6361:20054752


A&A 456, 323-327 (2006)
DOI: 10.1051/0004-6361:20054752

The periodic variations of a white-light flare observed with ULTRACAM

M. Mathioudakis1, D. S. Bloomfield1, D. B. Jess1, V. S. Dhillon2 and T. R. Marsh3

1  Department of Physics and Astronomy, Queen's University Belfast, Belfast, BT7 1NN, Northern Ireland, UK
    e-mail: M.Mathioudakis@qub.ac.uk
2  Department of Physics and Astronomy, University of Sheffield, Sheffield, S3 7RH, UK
3  Department of Physics, University of Warwick, Coventry, CV4 7AL, UK

(Received 22 December 2005 / Accepted 19 April 2006)

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 $\approx$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 $\approx$3.4 Mm and $\approx$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).


Key words: waves -- stars: activity -- stars: atmospheres -- stars: flare -- stars: individual: EQ Pegasi



© ESO 2006

Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.

Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.

Initial download of the metrics may take a while.