Pinpointing a stellar X-ray flare

using

XMM-Newton and VLT/UVES

Uwe Wolter

Hamburger Sternwarte

May 2008

J.U. NessJ. Robrade

J.H.M.M. Schmitt

The observations: Synchronizing orbits, night-time visibility, instrument schedules, …

2006 October 152006 October 14

Speedy Mic‘s rotation

VLT visibility

XMM orbit 1254

XMM observations

50 ks XMM-Newton data + 142 VLT/UVES spectra

Kürster 1994

v sin i = 132 ± 2 km/s( Wolter et al. 2005 )

P = 0.380 ± 0.004 d( Cutispoto et al. 1997 )

The target: Speedy Mic (BO Mic) A single K-dwarf - ultrafast and highly active

A giant flare (E > 1036 erg)

DSS, d ≈ 0.0002“

A „moderate“ flare in X-rays and optical

Total flare energy in soft X-rays: ~ 1034 erg

≈ 4.5 hours

Wolter et al. 2008

EPIC-pn

Rotation Phase

Ca K Equivalent width

Hα

Chromospheric emission

Rotational Modulation

Wolter & Schmitt 2005

Ca II K λ 3933 Ǻ

Evolution ofCa II K

Line Profiles

Rotation Phase

Wav

elen

gth

„unsharp masked“

1.7 Å @ 4000 Å

Rot

atio

n P

hase

Wavelength

9.4 h

A

C

B

C A

B

2006 flare

Flare heating and cooling

Wolter, Robrade et al. 2008; Reale et al.2004

Loop half length

240,000 km

≈ 0.4 R*

0.5 · log EM [cm-3]

log

T [

K]

A flare in a context

<<<<<<<<<<<

Wolter et al. 2008 ESO PR 53-2007

Phase 3.9 Phase 4.2

Phase 4.6

X-ray flare sites can be localized by simultaneous optical / UV Doppler imaging

Summary

Wolter, Robrade, Schmitt & Ness 2008, A&A 478, L12ESO Press Release 53/07 „Speedy Mic‘s Photograph“

Flare sites are not necessarily conspicuous otherwise

„ … on returning within 60 seconds was mortified

to find that it was already much … enfeebled.“

(R. Carringon 1859, MNRAS XX)

Appendix

Outlook: Chromospheric heating events

He I 5875, Ca II 3933 and XMM-pn at 300 s resolution

Rotation Phase

A „solar-like“ spectrum

Na D2 5889.97 Ǻ

Na D1 5895.94 Ǻ

Hβ 4861.34 Ǻ

Hα 6562.81 Ǻ

Ca II K 3933.68 Ǻ

Ca II H 3968.49 Ǻ

Arcturus (α Boo, K1 III, Teff

≈ 5200 K ) (NOAO)

e.g. Deutsch 1958, Vogt & Penrod 1983, Wolter 2004

The Doppler imaging principle:Line profiles → spatial information

Speedy Mic vs. Sun Ultrafast rotation and high activity

Valenti 2001, Sterzig & Schmitt 1997, Cardini et al. 2007, Balihunas et al. 1995

Sun

SpeedyMic

Lost and found

„Ultrafast rotators“

„Ultrafast rotators“

BO „Speedy“ Mic in 2002

(HD 197890)

Aug 2

„6400 Å“

Aug 7

„6400 Å“

Photometry 2002(SAAO)

The Prominences …

Evolution of Hα (Aug 2)

line profiles

Hα (Aug 2) Ca II K (Aug 2)

Hα (Aug 2)

„A densely packed prominence system beyond co-rotation“

Hα (July 19)

Dunstone et al. 2006 (adapted)

r = 3.5 ± 0.6 R*

r ≈ 5 ± 1.5 R*

Rk = 1.95 ± 0.07 R*

Collier Cameron & Robinson 1989Donati et al. 2000

RXJ 1508.6±4423 („post T Tauri“)Hα emissionAB Dor

Hα absorption transients

Stellar prominences

The Plage(s) …

φ = 112° θ = 130°

Localizing one stellar plage

Ca II K (Aug 2)

„Localizing one (?) stellar plage“

φ = 112° θ = 130°

φ = 72°θ = 99°

(Aug 7)

Ca II K (Aug 2)

The Flare …

APOD April 2006

„Astronomers love stars …“

„… and we have a fine one right near us.“

(Zirrin 1988)

DOT

Hα

Hα pre-flare Hα flare (21:06 UT)

Johns-Krull et al. 1997

The 1993 March 6 solar flare

„Unfortunately, the observer was eating lunch when the flare began.“

GOES „soft X-ray“

20:23

(near max.)

Solar flare Hα profiles

Another solar flare(Hα – 0.5 Å)

Zirrin 1988 (BBSO)

„after peak“

higher density

„raining down“