Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Simultaneous Kepler/K2 and XMM-Netwon observations of superflares in the
  Pleiades   Flares are powerful events ignited by a sudden release of magnetic energy.
With the aim of studying flares in the 125-Myr-old stars in the Pleiades
observed simultaneously in optical and X-ray light, we obtained new XMM-Newton
observations of this cluster during the observations of Kepler K2 Campaign 4.
Our objective is to characterize the most powerful flares observed in both
bands and to constrain the energy released in the optical and X-ray, the
geometry of the loops, and their time evolution. We aim to compare our results
to existing studies of flares occurring in the Sun and stars at different ages.
We selected bright X-ray/optical flares occurred in 12 known members of the
Pleiades from their K2 and XMM-Newton light curves. The sample includes ten K-M
stars, one F9 star, and one G8 star. Flare average properties were obtained
from integrated analysis of the light curves during the flares. The time
evolution of the plasma in the magnetic loops is constrained with time-resolved
X-ray spectral analysis. Most of the flares studied in this work emitted more
energy in optical than in X-rays, as in most solar flares, even if the Pleiades
flares output a larger fraction of their total energy in X-rays than typical
solar flares do. Additionally, the energy budget in the two bands is weakly
correlated. We also found comparable flare duration in optical and X-rays and
observed that rapidly rotating stars (e.g., with rotation period shorter than
0.5 days) preferentially host short flares. We estimated the slope of the
cooling path of the flares in the log(EM)-versus-log(T) plane. The values we
obtained are affected by large uncertainties, but their nominal values suggest
that the flares analyzed in this paper are mainly due to single loops with no
sustained heating occurring during the cooling phase. We also observed and
analyzed oscillations with a period of 500 s during one of the flares.

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The categories of this paper are: alg-geom
13
The categories of this paper are: quant-ph
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The categories of this paper are: atom-ph
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The categories of this paper are: solv-int
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The categories of this paper are: nlin
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The categories of this paper are: q-fin
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The categories of this paper are: dg-ga
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The categories of this paper are: mtrl-th
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The categories of this paper are: q-alg
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The categories of this paper are: acc-phys
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The categories of this paper are: eess
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The categories of this paper are: econ
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The categories of this paper are: cmp-lg
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The categories of this paper are: patt-sol
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The categories of this paper are: nucl-th
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The categories of this paper are: adap-org