1. Plasma diagnostics of a giant stellar flare Carolin Liefke 1 Birgit Fuhrmeister 1 Ansgar Reiners 1,2 Jürgen H.M.M. Schmitt 1 1 Hamburger Sternwarte, 2 Georg-August Universität Göttingen

2. Carolin Liefke - Plasma diagnostics of a giant stellar flare2/12 Outline The active M dwarf CN Leo XMM-Newton observations of a giant flare EPIC spectra –Evolution of flare plasma temperature and emission measure –Loop modelling –Development of iron abundance in the course of the flare RGS spectra –Densities from the O VII triplet –Neon triplet and abundance

3. Carolin Liefke - Plasma diagnostics of a giant stellar flare3/12 The active M dwarf CN Leo Close-by mid-M dwarf (T eff = 2800 K, spectral type M5.5), well-known flare star Shows persistent optical coronal Fe XIII line emission (Schmitt & Wichmann, 2001; Fuhrmeister & Schmitt 2003) Measured photospheric magnetic fields: Bf~2.2kG, with variations of ≈ 100 G observed (Reiners, Schmitt & Liefke, 2007) Six observations with XMM-Newton, simultaneous optical high-resolution spectroscopy with VLT/UVES Shows distinct periods of quiescence (at comparably low levels) and flaring in X-rays (Fuhrmeister, Liefke & Schmitt, 2007)

4. Carolin Liefke - Plasma diagnostics of a giant stellar flare4/12 Flux increases by factors up to 500 in the optical and up to 100 in X-rays The giant flare

5. Carolin Liefke - Plasma diagnostics of a giant stellar flare5/12 EPIC spectra

6. Carolin Liefke - Plasma diagnostics of a giant stellar flare6/12 Temperature and emission measure modelling Time-resolved spectral fitting with a two-temperature component model of collisionally-ionized diffuse plasma (vapec) Development of flare temperature (emission measure weighted average of the two components) and total emission measure of the flare plasma

7. Carolin Liefke - Plasma diagnostics of a giant stellar flare7/12 Loop length L = 1.7 · 10 9 cm according to the method of Reale et al. 1997 T Max = 5.6 · 10 7 K  = 0.70  = 237 s

8. Carolin Liefke - Plasma diagnostics of a giant stellar flare8/12 Fe abundance Quiescent iron abundance: 0.59 ± 0.07 (relative to Anders & Grevesse, 1989) Evaporated material shows strong enhancement of iron

9. Carolin Liefke - Plasma diagnostics of a giant stellar flare9/12 RGS spectra RGS 1RGS 2 Flare Quiescence

10. Carolin Liefke - Plasma diagnostics of a giant stellar flare10/12 Density variations  log n e ≈ 10, but consistent with low-density limit  log n e > 12 O VII triplet during quiescence and flare 20.8 ks1.4 ks

11. Carolin Liefke - Plasma diagnostics of a giant stellar flare11/12 Neon Neon triplet also consistent with density increase, but iron contamination prevents unambiguous conclusions Neon lines are weak in general, neon abundance is low: A Ne /A O = 0.24 ± 0.03 (Sun: A Ne /A O = 0.15, active stars: A Ne /A O ≈ 0.42)

12. Carolin Liefke - Plasma diagnostics of a giant stellar flare12/12 Conclusions A giant flare with a flux increase of a factor of 100 has been observed with XMM-Newton on the active M dwarf CN Leo Time-resolved X-ray spectroscopy with the EPIC instruments allows to investigate the development of temperature and emission measure of the flare plasma Loop length of 1.7 · 10 9 cm The iron abundance of the flare plasma is enhanced by a factor > 2 In O VII, the density of the flare plasma is increased by a factor of > 100 The neon abundance of CN Leo is comparably low in general