The X-ray spectra of the flaring and quiescent states of AT Microscopii observed by XMM-Newton^*

¹ SRON National Institute for Space Research, Sorbonnelaan 2, 3584 CA Utrecht, The Netherlands
² Astronomical Institute “Anton Pannekoek”, Kruislaan 403, 1098 SJ Amsterdam, The Netherlands
³ Columbia Astrophysics Laboratory, Mail code 5247, 550 West 120th Street, New York, NY 10027, USA
⁴ Paul Scherrer Institut, Würenlingen & Villigen, 5232 Villigen PSI, Switzerland

Corresponding author: A. J. J. Raassen, a.j.j.raassen@sron.nl

Received: 3 February 2003
Accepted: 29 August 2003

Abstract

The X-ray spectrum of the late-type M-dwarf binary AT Mic (dM4.5e+dM4.5e) is observed in the wavelength range 1–40 Å by means of rgs and epic-mos on board XMM-Newton. During the exposure a flare occured. We have performed a 3-temperature fit and a DEM-modeling to the flaring and quiescent part of the spectrum. We report the coronal temperature distribution, emission measures, and abundances of the flaring and quiescent state of this bright X-ray source. The temperature range stretches from about 1 to 60 MK. The total volume emission measure in this temperature interval is  cm^-3 for the quiescent state and  cm^-3 for the flare state. This difference is due to the contribution of the hot temperature component. The high-resolution spectrum of AT Mic, obtained by rgs, is dominated by the H- and He-like transitions of C, N, O, and Ne and by Fe xvii lines, produced by the plasma with temperatures from 1 to 10 MK. The epic-mos spectrum below 10 Å shows H- and He-like Ne, Si and the iron K-shell transitions. They are produced by the hot component (30 MK). The iron K-shell is more prominent in the flare state. The abundance pattern in the quiescent state of AT Mic shows the depletion of low-FIP elements relative to high-FIP elements, indicating the presence of an I(nverse)FIP effect in this active star. In the flare state, however, some flattening of this IFIP effect is present.