pinpointing a stellar x-ray flare using xmm-newton and vlt/uves uwe wolter hamburger sternwarte may...
TRANSCRIPT
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“