SNRs using Xray morphology and spectra Hiroya Yamaguchi HarvardSmithsonian Center for Astrophysics Classification of SN Progenitors Optical obs of SNe Classification is relatively straightforward ID: 382232
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Slide1
Constraining progenitors of SNRs using X-ray morphology and spectra
Hiroya Yamaguchi
Harvard-Smithsonian Center for AstrophysicsSlide2
Classification of SN Progenitors
Optical
obs
of
SNe
Classification is relatively
straightforward- Spectrum (historically well established) - Luminosity (56Ni yield)
X-ray obs of SNRs
Classification (Ia/CC) is (was) controversial in many SNRs- Similar X-ray luminosity- Morphology? SNRs can be spatially resolved, strong advantage of X-ray- Spectrum?
SNe
Ia
: nuclear reaction energy ~ 1051 erg
SNe CC: gravitational energy ~ 1053 erg 99% neutrino + 1% kinetic (~ 1051 erg)
Ia (SD)
Ia (DD)
CC (1987A)
=> transformed to thermal energy (X-ray luminosity)Slide3
Type Ia
CC
Ellipticity
Mirror
asymmetricity
Morphology of
SNRs
CC
SNRs are more asymmetric than Ia SNRs (Lopez+09;11)
G344.7
-
0.1 found
to be Type Ia (HY+12)Chandra images of Galactic/Magellanic
SNRsReflects nature of explosion and/or environment?
SNR E0102-72 (CC)
0104-72.3 (Ia candidate)
Doesn’t work for SMC SNRs
… (Lopez+12)
0104-72.3
E
0102-72Slide4
X-Ray Spectra of SNRs
Advantage
- Optically thin (self absorption is almost
negligible, but see Miyata+08)
- K-shell emission from He- & H-like atoms
(kT
e ~ hn ~ 0.1–10 keV, comparable to K-shell potential), so physics is simple
Si
S
Ar
Ca
Fe
Ni
Mg
Ne
Artificial
features
(a sort of
bgd
)
Simple Quiz
CC (W49B)
Ia
(SN1006)
YOU LOSE
m9(^Д^)
Suzaku
spectrum
of
Tycho
(Hayato+10)Slide5
X-Ray Spectra of SNRs
Si
S
Ar
Ca
Fe
Ni
Mg
Ne
Artificial
features
(a sort of
bgd)
W49B (CC)
Large foreground
extinction makes
O/Ne/Mg emission in W49B
weak
Absorption for
different column
density (N
H
[cm
-2
])
SN1006
W49B
Note: although we use N
H
to describe
the column, what we measure in
X-rays is the column of
metals
Yet, weakness of Fe emission in
SN 1006 (
Ia
SNR) is puzzling
=> Understanding of NEI
is essentialSlide6
Non Equilibrium in Ionization (NEI)
Pre-shocked metals in ISM/
ejecta
are
almost neutral (unionized)
Shock-
heated electrons gradually ionize atoms by collision, but ionization proceeds very slowly compared to heating
Fe ion population
in NEI plasma for
kTe = 5 keV
ne
t (cm-3 s)Ion fraction
Fe24+
Fe25+
Fe
26+
Fe
16+
lowly
ionized
high
ly
ionized
Fe
24+
Fe
25+
Fe
26+
Fe
16+
Electron temperature
kT
e
(
keV
)
CIE
n
e
t
: “ionization age”
n
e
:
electron density
t
: elapsed time since gas
was heatedSlide7
Non Equilibrium in Ionization (NEI)
Fe ion
population
in
NEI
plasma for kTe
= 5 keVne
t (cm-3 s)
Ion fractionFe24+Fe25+
Fe
26+
Fe
16+
lowly ionizedhighly ionized
net : “ionization age”
ne : electron density
t : elapsed time since gas was heated
Timescale to reach CIE for ISM
t
~ 3
x
10
4
(n
e
/1 cm
-3
)
-1
yr
As for
e
jecta
…
Time when the masses of swept-up
ISM
and
ejecta
becomes comparable
Ionization state for the
ejecta
becomes almost
“frozen”
after an SNR evolved.
Ionization age for the
ejecta
strongly depends
on the
initial CSM density
rather than its age.Slide8
Non Equilibrium in Ionization (NEI)
Full X-ray band
Magnified spectra in the
6-7
keV
band
(Fe
K
emission)
Fe-L blend
Fe-K
Observed
spectrum (Convolved by
Suzaku
response)
n
e
t = 5x10
9
1x10
10
5x10
10
1x10
11
3x10
11
Ar
-like
Ne-like
C-like
Be-like
He-like
Model spectra of Fe emission [
kT
e
= 5
keV
]
How does ionization age affect a spectrum?
How can we measure ionization age?
H-
like
6.42
keV
6.44
keV
6.60
keV
6.64
keV
6.67
keV
6.0
7
.0
0.5
10Slide9
Si
S
Ar
Ca
Fe
Ni
Mg
Ne
Artificial
features
(a sort of
bgd
)
Ozawa+2009
HY+2008,
Uchida+, in prep.
SN1006 (Type
Ia
SNR) W49B (CC SNR)Slide10
SN1006: Searching for Fe emission
Fe?
BeppoSAX
MECS
spectrum
Chandra image
Prototypical Type
Ia SNR, but emission from Fe has never been detected.
- Only one possible detection reported by BeppoSAX
- XMM-Newton failed to detect
Vink+00
Suzaku
spectrum(HY+08)
Detected! but weak despite of its Type
Ia originFe-K
centroid ~ 6420eV (< Ne-like) … Corresponding net is ~ 1
x
10
9
cm
-3
s
Fe
24+
Fe
25+
Fe
26+
Fe
16+Slide11
SN1006: Multiple net Components in Si
Approx with 2-
n
e
t
components
for Si and S ejecta net1 ～ 1×1010
cm-3 s net2
～ 1×109 cm-3 s cf. Fe: net ～ 1×109 cm-3 s
Si ion fraction
@1keV
Si
12+Si
13+Si6+
Si8+
C~O-like
He-like
Mg
Si
broad feature
S
Reverse shock heats from outer region
Outer
ejecta
= highly ionized
Inner
ejecta
= lowly ionizedSlide12
SN1006: Fullband Spectrum & Abundances
ISM
(
w
/ solar
abundance)
Outer ejecta (ne
t ~ 1010 cm-3
s)Inner ejecta (net ~ 109)Non-thermal
(synchrotron)
Fe
Derived abundance ratios compared
to the W7 model of Nomoto+84
Outer
ejecta
Inner ejecta
Suggests stratified composition with Fe toward the
SNR center,
which results in the lowly-ionized (thus weak) Fe emission
HY+08Slide13
Ejecta Stratification in Type Ia SN/SNRs
XMM image of
Tycho
Radius (
arcmin
)
Radial
profile
FeSi
Color: Si-K
Contour: Fe-K
Decourchelle+01
Mazzali+07
IME
56
Ni
Enclosed mass
SN 2003du
(
Tanaka+10)
See also
Badenes+06Slide14
Si
S
Ar
Ca
Fe
Ni
Mg
Ne
Artificial
features
(a sort of
bgd
)
Ozawa+2009
HY+2008,
Uchida+, in prep.
SN1006 (Type
Ia
SNR) W49B (CC SNR)Slide15
W49B: Peculiar Ionization State
- RRC can be enhanced only when
the plasma is
recombining
(e.g., photo-ionized plasma)
Similar recombining SNRs - IC443 (HY+09) - SNR 0506-68 (Broersen+11) - other 3 & a few candidates“Recombining NEI” in
SNRs is not unique => Need to define “recombination age”
CrMnHe-like Fe Ka
Ni + Fe K
b
Fe-K RRC
H-like Fe
Ozawa+09Ejecta is highly ionized to be He-likeRadiative recombination continuum
Fe25+ + e- → Fe24+ + h
n … indicates presence of a large fraction
of H-like Fe
Measured
kT
e
~
1.5
keV
Temperature (
keV
)
Fe
24+
Fe
25+
Fe
26+
Fe
16+
Fe ion population in a
CIE
plasmaSlide16
W49B: Possible Progenitor
blast wave
2nd reverse shock
reverse shock
Blast wave
b
reakout into ISM
BW speed becomes faster and expand
adiabatically, resulting in rapid cooling with “frozen” ionization state Shimizu+12Explosion in dense CSM
- Numerical (Shimizu+12)
- Analytical, more progenitor- oriented (Moriya 12)
RSG case (
vw ~ 10 km/s)
WR case (vw ~ 1000 km/s)Type II-P or IIn
could be a progenitor of a recombining SNR (Moriya 12)Slide17
Fe-K diagnostics
Extreme cases have been shown
SN1006: Type
Ia
SNR,
Fe lowly-ionized due to a low ambient density and ejecta stratification with Fe more concentrated toward the center W49B: CC SNR, Fe over-ionized (recombining),
possibly due to interaction with high-density CSM … and inhomogeneous ejecta structure?
Red: SiBlue: FeGreen: continuum
Other SNRs?Slide18
Fe-K diagnostics
Type
Ia
CC
- Type
Ia
and CC
SNRs are clearly separated (CC more ionized)- Luminosity of both groups are distributed in the similar range.
(HY+, in prep.)
n
e
t = 5x10
9
1x1010 5x1010 1x1011 3x1011
Can be explained by ionization (and temperture, density effects)
--- Measuring ionization state is essential for measuring
element abundances!!Slide19
Fe-K diagnostics
Type
Ia
CC
(HY+, in prep.)
Ionization ages expected if the
SNRs
have evolved in uniform ISM with
typical density
Hachisu+01
Badenes+07
If the SD scenario is the case, a large, low-density
cavity is expected around the progenitor No evidence of an “accretion wind” and a resultant cavity but for a few
Type Ia SNRsSlide20
Evidence of cavity/CSM in Ia SNRs
RCW86 (Williams+11)
Unique
Ia
SNR where the presence of
a surrounding cavity is suggested
Kepler
(Reynolds+07)
N103B (Lewis+03)Slide21
Summary
X-ray observation of
SNRs
is one of the best methods to study
stellar/
explosive nucleosynthesis. (optically-thin, K-shell emission)- Understanding of non-equilibrium in ionization is, however, essential for accurate measurement of element abundances.
- Fe emission in Type Ia SNRs is commonly weak due to low-density ambient and stratified chemical composition.- In CC SNRs, on the other hand, Fe is highly ionized, sometime
overionized, possibly due to initial CSM interaction.- No evidence of a large cavity expected from an “accretion wind” around Type Ia
SNRs, except for RCW86, constraining progenitor system??