Pinpointing a stellar X-ray flare using XMM-Newton and VLT/UVES
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Transcript of Pinpointing a stellar X-ray flare using XMM-Newton and VLT/UVES
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
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]
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)
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
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
APOD April 2006
„Astronomers love stars …“
„… and we have a fine one right near us.“
(Zirrin 1988)
DOT
Hα