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A&A 416, 733-747 (2004)
DOI: 10.1051/0004-6361:20034027
Modeling an X-ray flare on Proxima Centauri: Evidence of two flaring loop components and of two heating mechanisms at work
F. Reale1, M. Güdel2, G. Peres1 and M. Audard31 Dipartimento di Scienze Fisiche & Astronomiche, Sezione di Astronomia, Università di Palermo, Piazza del Parlamento 1, 90134 Palermo, Italy
e-mail: peres@astropa.unipa.it
2 Paul Scherrer Institut, Würenlingen & Villigen, 5232 Villigen PSI, Switzerland
e-mail: guedel@astro.phys.ethz.ch
3 Columbia Astrophysics Laboratory, Columbia University, 550 West 120th Street, New York, NY 10027, USA
e-mail: audard@astro.columbia.edu
(Received 30 June 2003 / Accepted 2 December 2003 )
Abstract
We model in detail a flare observed on Proxima Centauri with the EPIC-PN on board XMM-Newton at high statistics and high time
resolution and coverage. Time-dependent hydrodynamic loop modeling is used to describe the rise and peak of the light curve,
and a large
fraction of the decay, including its change of slope and a secondary maximum, over more than 2 h. The light curve, the emission
measure and the temperature derived from the data allow us to
constrain the loop morphology and the heating function and to show that this flare can be described with two components: a
major one triggered by an intense heat pulse injected in a single flaring loop with half-length
cm, the other one by less intense heat pulses released about 1/2 h after the first one in related loop systems, probably
arcades, with the same half-length. The heat functions of the two loop systems appear very similar: an intense
pulse located at the loop footpoints followed by a low gradual decay distributed in the coronal part of the loop. The latter
result and the similarity to at least one solar event (the Bastille Day flare in 2000) indicate that this pattern may be common
to solar and stellar flares.
Key words: stars: flare -- stars: coronae -- X-rays: stars -- hydrodynamics
Offprint request: F. Reale, reale@astropa.unipa.it
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