Download Shocking Truth about Massive Stars Lidia Oskinova Chandra’s First Decade of Discovery

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Shocking Truth about Massive Stars
Lidia Oskinova
Wolf-Rainer Hamann & Achim Feldmeier
Potsdam University, Germany
ACIS Raw Detector Image of O-type supergiant ζ Puppis, CXO archive
Chandra’s First Decade of Discovery
22 - 25 September 2009, Boston, Massachusetts, USA
Massive Stars and Stellar Winds
Initial mass
M∗ > 15M⊙
Main Sequence: OB-type
Fast evolution (~Myr)
star formation
trace
Hot. T eff > 10 000 K
high surface brightness
→
Photon momentum →
acceleration of matter
Radiative acceleration larger
than gravitation →
supersonic STELLAR WIND
nasaimages.org
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OB stars are X-ray active (Einstein observatory 1978)
Hot stars: radiatively driven stellar winds
Supersonic stellar winds are intrinsically unstable
Shocks
Heating
X-Rays
Shocks also result from:
Collision of streams
in magnetically confined wind
Collision of winds
in binaries
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X-Ray Spectroscopy of Massive Stars ζ Ori
Prediction of hydrodynamic models
NASA/EIT/W.Waldron, J.Cassinelli
Models predict:
X-ray emitting plasma (T X =
1...10 MK) permeated with
warm (T = 10 kK) absorbing
wind
X-rays originate at few R
*
from the core
X-ray spectroscopy is needed!
Distance [R ]
Feldmeier et al. 1997
Photo: G. Emerson, E.E. Barnard Observatory
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Chandra is in Orbit!!!
Cheering crowd
prague-life.com
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O-type stars
NVII
OVII
OVIII
FeXVII
FeXVII
OVIII
FeXVII
NeIX
FeXVIII
NeX
NeX
MgXI
MgXII
SiXIV
SiXIII
SXV
07
ζ Pup
O4I
0.2
0.1
0.0
ζ Ori
O9.7I
o
normalized counts/sec/A
0.1
0.0
0.03
ξ Per
O7.5III
0.02
0.01
0.00
0.10
ζ Oph
O9V
0.05
0.00
4
6
8
10
12
14
16
o
Wavelength (A )
18
20
22
24
26
Oskinova etal. 2007
08
Analyses of the HETGS spectra
Emission line profiles
Broad; width scales with wind speed
Line formation: deep in the wind
Similar accross the spectrum
Clumped wind treatment is needed
FIR line ratios
Formed close to the photosphere
Temperature decreases outward
Abundances
Agree with wind abundances
Wojdowski & Schulz (2005), Oskinova etal (2006),
Waldron & Cassinelly (2007), Zhekov & Palla (2007), etc.
v∞ = 2450 km/s
ξ Per
o
O7.5III
0.02
0.01
0.00
0.12
v∞ = 1550 km/s
0.10
o
Range from 2 MK to 10 MK
Flux (Counts/sec/A )
Temperature
Flux (Counts/sec/A )
0.03
ζ Oph
O9V
0.08
0.06
0.04
0.02
0.00
12.0
12.1
12.2
o
Wavelength (A )
09
Wind-shock Theory has Predictive Power
UV and X-ray spectra
P V 3p 2 P - 3s 2 S
1.5
microclumping
PV resonance doublet
Rel. Flux
micro- & macroclumping
Mass-loss rates!
1.0
X-ray line profiles
0.5
X-ray spectra
0.0
1100
1110
1120
1130
o
λ/A
1140
Oskinova et al. 2007
0.20
DEM distribution
Ç
same M
Normalized Flux
o
10
clumped wind
Flux (Counts/sec/A )
8
0.2
−4
7
10
T [K]
−8
6
10
−12
0.1
smooth
wind
5
10
0
5
10
15
x = r/R∗
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Krticka et al. 2009
25
30
0.0
−1.0
−0.5
0.0
0.5
Normalized Frequency
Oskinova et al.
0.15
ζ Pup
NeX
0.10
0.05
0.00
1.0 12.0
12.1
12.2
o
Wavelength (A )
10
B-
11
15
16
17
18
α Cru
OVII
OVIII
FeXVII
FeXVII
OVIII
FeXVII
20
21
NVII
19
22
23
24
α Cru
37
38
25
26
27
28
29
30
31
32
33
39
40
41
42
43
44
45
46
o
Wavelength A
47
48
35
36
FeXVI
SiX
FeXVI
24
SiXI
MgX
23
SiXI
FeXVII
SiX
Normalized counts
CVI
14
NVII
13
FeXVIII
NeIX
Chandra observations of α Cru
34
49
50
51
X-ray brightest massive star
on sky
B0.5IV+BV at d=98 pc
Companion B1V
Soft spectrum T X =1..3 MK
37
52
Oskinova et al. in prep.
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Stationary plasma in B-stars
Wind speed is 1500 km/s
But lines are narrow Comparable to
instrumental profile!
He−like ions: f/i line ratio probes
distance to stellar photosphere
Flux (Counts/sec/Angstrom)
OVII
α Cru
Capella
λR
0.0
21.5
21.6
λI
21.7
21.8
X−ray plasma in B−stars
Close to the
photosphere
Stationary
Different from shocks
in O−type winds
Pulsations? Coronae?
λF
21.9
22.0
22.1
22.2
12a
The evolution of (very) massive stars
7
100
T eff / kK
50
20
10
5
Mass removal by wind drives
the evolution
OB
(short LBV)
WR
Winds are getting dense
and more enriched
log L / L
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WR
Wolf−Rayet (WR) stars
LBV
OB
40 M
WN
→
WC
→
WO
→
SN
5
ZAM
S
4
5
4
log T eff / K
Credit: NASA/CXC/SAO/F.Seward et al
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WR124
WN8−type
Observed serendipitously by Chandra
WN8 stars are X−ray quiet
Wolf-Rayet type stars
Image courtesy of D.Ducros and ESA
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X-ray view on Wolf-Rayet Stars
Not all WN−type stars emit X−rays. Lack of X−rays cannot be
attributed only to the wind opacity (Oskinova et al. ’06)
X−ray spectra of single WN stars are harder than spectra of
O−stars (Ignace et al. 2003)
Single WC stars are X−ray quiet (Oskinova et al. 2003)
X−ray bright WR stars are binaries (Oskinova & Hamann
2008)
ζ Pup (O−type)
WR 1 (WN)
WR 114 (WC)
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Closest WO-type Star WR142 in the Star Cluster Berkeley 87
Combined Spitzer (red+green) and EPIC (blue) image of the SFR ON 2
Only three WO
stars are known
in the MW
WO is the latest
possible
evolutionary
stage of massive
star
Core−collapse
within 10 000 yr
WR 142
Oskinova et al. in prep.
Strongly
influence their
environment
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Glimpse at the pre core-collapse star
Rel. Flux
9.54
8.89
8.60
-14
7.63
7.23
7.10
-15
2
1
0
6.69
He II 5 - 4
3
-13
o
log F λ [erg s -1 cm -2 A -1 ]
-12
10000
10500
λ/A
o
-16
5.35
-17
3.5
Oskinova et al. 2009
4.0
4.5
o
log λ / A
5.0
5.5
Requires state−of−the art non−LTE models to fit
observed optical and UV spectra. Such as PoWR code
(Hamann et al. 2006)
T =160 kK, R =0.5R , wind speed v=6000 km/s
*
*
Our analysis indicates that star may be a FAST
ROTATOR V rot sin i =4000 km/s. Current mass ~10 M
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Discovery of X-ray emission from a WO-type star
Strong enhancement by CO
*
opaque for the X−rays
*
winds should be very
X-rays are too hard to be explained by wind shocks
Hint on the presence of magnetic field B(r=2R ) > 7 kG
*
*
Chandra detects hard X−rays from another compact fast
*
rotator WR2 (WN2)
0.00300
0.00250
0.00200
0.00150
0.00100
WR142
0.00050
1.0
Oskinova et al. (2009)
2.0
3.0
4.0
5.0
keV
6.0
7.0
8.0
Mystery of X-rays from WR stars: Connection With Collapsars (?)
’’A very energetic explosion of a massive star is likely to create a ...
fireball.... the inner core of a massive, rapidly rotating star
collapses into a ~10 M Kerr black hole ... A superstrong ~10 15 G
magnetic field is needed to make the object ... a microquasar. Such
events must be vary rare...to account for the ... GRBs’’
Do we indeed observe in our Galaxy massive, magnetic,
rapidly rotating stars on latest stages of their evolution ?
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Shocking truth?
O−stars: X−rays are generated by
wind shocks
B−stars: not clear: magnetic
fields, pulsation, winds.
WR−stars: no hi−res spectrum
exists! Magnetic field, rotation.
X−rays are sensitive probe of stellar
winds
Generation of X−rays in stellar winds is
important physical problem
X−rays provide insights in stellar
structure and evolution
Chandra