classification of sn progenitors optical obs of sne classification is relatively straightforward -...
TRANSCRIPT
Constraining progenitors of SNRs using X-ray
morphology and spectra
Hiroya YamaguchiHarvard-Smithsonian Center for
Astrophysics
Classification of SN Progenitors
Optical obs of SNeClassification is relatively straightforward
- Spectrum (historically well established) - Luminosity (56Ni yield)
X-ray obs of SNRsClassification (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)
Type Ia
CC
Elli
pti
cit
y
Mirror asymmetricity
Morphology of SNRsCC 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 SNRs
Reflects 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
E0102-72
X-Ray Spectra of SNRsAdvantage- Optically thin (self absorption is almost negligible, but see Miyata+08)- K-shell emission from He- & H-like atoms (kTe ~ hn ~ 0.1–10 keV, comparable to K-shell potential), so physics is simple
Si
SArCa 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)
X-Ray Spectra of SNRs
Si
SArCa 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 (NH [cm-
2])
SN1006
W49B
Note: although we use NH 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 essential
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
net (cm-3 s)
Ion f
ract
ion Fe24+
Fe25+
Fe26+
Fe16+lowly ionized
highly ionized
Fe24+
Fe25
+
Fe26+Fe16
+
Electron temperature kTe (keV)
CIE
net : “ionization age” ne : electron density
t : elapsed time since gas was heated
Non Equilibrium in Ionization (NEI)Fe ion population in NEI plasma for kTe = 5 keV
net (cm-3 s)
Ion f
ract
ion Fe24+
Fe25+
Fe26+
Fe16+lowly ionized
highly ionized
net : “ionization age” ne : electron density
t : elapsed time since gas was heated
Timescale to reach CIE for ISM t ~ 3 x 104 (ne/1 cm-3)-1 yr
As for ejecta…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.
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)
net = 5x109 1x1010 5x1010 1x1011 3x1011
Ar-like Ne-like C-like Be-likeHe-like
Model spectra of Fe emission [kTe = 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 10
Si
SArCa Fe
Ni
Mg
Ne
Artificial features(a sort of bgd)
Ozawa+2009HY+2008, Uchida+, in prep.
SN1006 (Type Ia SNR) W49B (CC SNR)
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 origin
Fe-K centroid ~ 6420eV (< Ne-like) … Corresponding net is ~ 1 x 109 cm-3 s
Fe24+
Fe25+
Fe26+
Fe16+
SN1006: Multiple net Components in Si
Approx with 2-net componentsfor Si and S ejecta
net1 ~ 1×1010 cm-3 snet2 ~ 1×109 cm-3 s
cf. Fe: net ~ 1×109 cm-3 sSi ion fraction @1keV
Si12+
Si13+
Si6+ Si8+
C~O-like He-like
MgSi
broad feature
S
Reverse shock heats from outer region
Outer ejecta = highly ionizedInner ejecta = lowly ionized
SN1006: Fullband Spectrum & Abundances
ISM (w/ solar abundance)Outer ejecta (net ~ 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+08
Ejecta Stratification in Type Ia SN/SNRsXMM image of Tycho
Radius (arcmin)
Radial profile
Fe
Si
Color: Si-KContour: Fe-K
Decourchelle+01
Mazzali+07IME
56NiEncl
ose
d m
ass
SN 2003du(Tanaka+10)
See also Badenes+06
Si
SArCa Fe
Ni
Mg
Ne
Artificial features(a sort of bgd)
Ozawa+2009HY+2008, Uchida+, in prep.
SN1006 (Type Ia SNR) W49B (CC SNR)
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”
Cr Mn
He-like Fe Ka
Ni + Fe Kb
Fe-K RRC
H-like Fe
Ozawa+09
Ejecta is highly ionized to be He-like
Radiative recombination continuumFe25+ + e- → Fe24+ + hn
… indicates presence of a large fraction
of H-like FeMeasured kTe ~ 1.5 keV
Temperature (keV)
Fe24+
Fe25+
Fe26+Fe16+
Fe ion population in a CIE plasma
W49B: Possible Progenitor
blast wave
2nd reverse shock
reverse shockBlast wave breakout 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)
Fe-K diagnosticsExtreme 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?
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.)
net = 5x109 1x1010 5x1010 1x1011 3x1011
Can be explained by ionization (and temperture, density effects) --- Measuring ionization state is essential for measuring element abundances!!
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 SNRs
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)
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??