Modeling Ejecta in Supernova
Remnant X-Ray Spectra
John P. Hughes
Rutgers University
 Cara Rakowski, Rutgers
 Parviz Ghavamian, Rutgers
 Jessica Warren, Rutgers
 Pat Slane, CfA
 Dave Burrows, Penn State
 Sangwook Park, Penn State
 John Nousek, Penn State
 Gordon Garmire, Penn State
 Peter Roming, Penn State
 Anne Decourchelle, Saclay
December 16, 2002
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Where’s the Ejecta?
Optical: SNRs with high velocity oxygen-rich features
Galactic: Cas A, G292.0+1.8, Puppis A
LMC/SMC: N132D, E0540-69.3, E0102.2-72.2
Other: an unresolved SNR in NGC 4449
 Remnants of historical SNe
e.g., SN1006, SN1572 (Tycho), SN1604 (Kepler)
Based on [Fe II] in absorption; X-ray spectra
 Ejecta-dominated SNRs
e.g., W49B, G352.7-0.1, G337.2-0.7, G309.2-0.6
Based on X-ray spectra (mostly ASCA)
 Nearly all remnants up to ages of at least ~10,000 yrs!!!
N49, N63A, DEM71, N49B, and E0103-72.6
Based on Chandra spectro-imaging
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Thermonuclear Supernovae
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SN Ia (Hoyle & Fowler 1960)
– No hydrogen, a solar mass of 56Ni, some
intermediate mass elements (O, Mg, Si, S,…)
– Subsonic burning (deflagration) of approx.
one Chandrasekhar mass of degenerate C/O
– C-O white dwarf accreting H/He-rich gas from
a companion
– No compact remnant
– Mean rate ~ 0.3 SNU
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SN Ia Integrated Yields
Iwamoto et al, 1999, ApJS, 125, 439
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SN Ia Yields vs. Radius
Mass (Msun)
O 0.056-0.143
Ne 0.0008-0.0045
Mg 0.027-0.0158
Si 0.142-0.279
Fe 0.648-0.834
Iwamoto et al, 1999, ApJS, 125, 439
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Core Collapse Supernovae

SN II, SN Ib/c (Zwicky & Baade 1934)
– Massive stars that explode with (SN II) or
w/out (SN Ib/c) their H envelopes
– Photodisintegration of Fe, plus electron
capture on nuclei, remove central P support
– Core collapses, leading to NS or BH
– Core stiffens, rebounds and drives an outward
moving shock
– Neutrinos or jets needed to produce explosion
– Mean Rate ~ 1.3 SNU
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Nucleosynthesis in CC SNe
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Hydrostatic nucleosynthesis
– During hydrostatic evolution of star
– Builds up shells rich in H, He, C, O, and Si
– Amount of C, O, Ne, Mg ejected varies strongly with
progenitor mass
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Explosive nucleosynthesis
– Some mechanism drives a shock wave with 1051+ erg
through the Fe-core
– Burning front T’s of ~109 K cause explosive O- and Siburning
– Only affects the central parts of the star – outer
layers retain their pre-SN composition
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Explosive Nucleosynthesis
Process
T (109 K)
Main Products
Explosive complete Si-burning
5.0
“Fe”, He
Explosive incomplete Si-burning
4.0
Si, S, Fe, Ar, Ca
Explosive O-burning
3.3
Explosive Ne/C-burning
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1.2
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O, Si, S, Ar, Ca
O, Mg, Si, Ne
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Typical Mass Fractions
Element
O
Ne
Mg
Si
S
Ar
Ca
Fe
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Ex Ne
0.72
0.13
0.09
0.02
Ex O
0.45
0.005
0.30
0.20
0.025
0.02
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Ex Si-i
Ex Si-c
0.40
0.25
0.06
0.05
0.20
0.70
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Major Yields (in Solar Masses)
Element
13 Mo
15 Mo
20 Mo
25 Mo
C
0.060
0.083
0.115
0.148
O
0.218
0.433
1.480
3.00
Ne
0.028
0.039
0.257
0.631
Mg
0.012
0.046
0.182
0.219
Si
0.047
0.071
0.095
0.116
S
0.026
0.023
0.025
0.040
Ar
0.0055
0.0040
0.0045
0.0072
Ca
0.0053
0.0033
0.0037
0.0062
Fe
*0.150*
*0.130*
0.075
*0.050*
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SN II Yields vs. Radius
20 Msun model
Hydrostatic nucl.
M>2.05
Explosive nucl.
~1.6 <M<2.05
Mass cut set so
0.075 Msun of Fe is
ejected
Thielemann, Nomoto, and Hashimoto, 1996, ApJ, 460, 408
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Uncertainties

Thermonuclear SNe
– Physics of flame front propagation
– Precise progenitor system unknown – rate of
accretion and composition unknown

Core Collapse SNe
– Explosion mechanism unknown
– Location of mass cut (compact object/ejecta)
– Convection during He-burning
– 12C(a,g)16O reaction rate
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Useful General References
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Trimble 1982, Rev Mod Phy, 54, 1183 (Supernovae Part I)
Trimble 1983, Rev Mod Phy, 55, 511 (Supernovae Part II)
Bethe 1990, Rev Mod Phy, 62, 801 (Supernova Mechanisms)
Arnett 1996, “Supernovae and Nucleosynthesis” (Princeton
University Press: Princeton)
Wallerstein et al, 1997 Rev Mod Phy, 69, 995 (update of B2FH)
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X-ray Emission/Atomic Processes
Continuum emission – thermal bremsstrahlung:
Line emission:
Abundance
of element Z
December 16, 2002
Ionization fraction
of ion i
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Abundance Determination Issues

Thermodynamic State
– Nonequilibrium Ionization (net~105 cm-3 yr)
– T, n evolution with time/radius (e.g., Sedov)
– Other effects:
 Heating/cooling in pure element ejecta
 Te/Tp
 Nonthermal particle (rates and excitation)
– Absolute abundances (e.g., Si/H, O/H, Fe/H)
 Rely on assumption of H/He-dominated continuum
– Relative abundances (e.g., Mg/Si, O/Fe)
 OK, if species have the same spatial distribution
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Ejecta Mass Determination Issues
Volume estimation
 Clumping (reduces actual mass)
 Distance (M~D5/2)
 Source of electrons

–
–
–
–
Measure EM = nenIV
Solar abundance: ne ~ nH ~ nFe/107.6-12 ~ 25000nFe
Pure Fe: ne ~ 20nFe
Inferred Mpure Fe /Msolar ~ 35
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Overturning Our View of Cas A
Hughes, Rakowski, Burrows, and Slane 2000,
ApJL, 528, L109.
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Oxygen-Rich SNR G292.0+1.8
Park et al 2001, ApJL, 564, L39
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Oxygen-Rich SNR G292.0+1.8
Ejecta
Rich in O, Ne, and Mg, some Si
[O]/[Ne] < 1
No Si-rich or Fe-rich ejecta
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Oxygen-Rich SNR G292.0+1.8
Normal Composition, CSM
Central bright bar – an axisymmetric
stellar wind (Blondin et al, 1996)
Thin, circumferential filaments enclose
ejecta-dominated material – red/blue
supergiant winbd boundary
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Oxygen-Rich SNR G292.0+1.8
Point source
Featureless power-law spectrum, photon
index = 1.7
Surrounded by diffuse X-ray/radio nebula
Off center, implied speed of ~800 km/s
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PSR J1124-5916 in G292.0+1.8
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Discovered at Parkes (Camilo et al 2002)
P=0.1353140749 s, dP/dt=7.471E-13
Characteristic age ~ 2900 yrs (SNR age ~ 1600 yrs)
Not detected in coherent FFT of Chandra HRC observation
3.5 sigma detection from Zn2 test at radio parameters
Only ~130 pulsed events in 50 ks
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PSR J1124-5916
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Image Analysis: point source and elliptical gaussian (small nebula)
Point source contains ~160 X-ray events
Pulsed fraction high ~80%
Unpulsed point source emission < 1.4E-3 cts/s
LBB< 1033 erg/s
Below standard cooling curve for 2000 yr old PSR
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DEM L71: Ejecta and Shock Physics
Chandra/NASA
Soft X-ray
Rutgers Fabry-Perot/NOAO
Hard
H alpha
X-ray
Hughes, Ghavamian, Rakowski, and Slane, ApJL, 582, in press (10 Jan 2003)
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Fe-Rich Ejecta
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Properties of DEM L71 Ejecta
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Outer rim: lowered abundances, ~0.2 solar (LMC ISM)
Core: enhanced Fe abundance, [Fe]/[O] > 5 times solar (ejecta)
Thick elliptical shell, 32” by 40” across (3.9 pc by 4.8 pc)
Dynamical mass estimate
Wang & Chevalier 2001
r’ ~ 3.0
Mej = 1.1 Mch (n/0.5 cm-3)

EM mass estimate
EM ~ ne nFe V
MFe < 2 Msun

Main error: source of electrons
Fe-rich, low mass
December 16, 2002
SN Ia
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DEM L71: Shock Physics
Nonradiative Balmer-dominated shock
Measure post-shock proton temperature
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X-ray emission from thermal bremsstralung
Measure post-shock electron temperature
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Nonradiative Balmer Shocks
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Nonradiative means that a radiative
(cooling) zone does not form
Low density (partially neutral) gas
High velocity shocks
Narrow component: cold H I overrun by
shock, collisionally excited
Broad component: hot postshock
protons that charge exchange with cold
HI
(Chevalier & Raymond 1978; Chevalier, Kirshner, &
Raymond 1980)
Ghavamian, Rakowski, Hughes, and Williams
2002, ApJ, submitted.
December 16, 2002
Width of broad component yields post
shock proton temperature
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Constraining the Electron Temperature
Fit NEI shock models to 3 spatial
zones to follow evolution of Te
 Study 5 azimuthal regions with
sufficient Chandra statistics and
broad Halpha component
 Available data cannot constrain Te
gradients


Data do determine mean Te
Suggest partial to compete
temperature equilibration

Rakowski, Ghavamian, Hughes, & Williams 2002,
ApJ, submitted.
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Results on Te/Tp from DEM L71
Shows trend for higher equilibration for lower speed shocks
 X-ray/Halpha results consistent with other purely Halpha ones
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N63A

Middle-aged SNR
– 34” (8.2 pc) in radius
– 2000-5000 yrs old
– 2nd brightest LMC SNR

“Crescent”-shaped features
– Similar to features in Vela
– Clumps of high speed ejecta
– Not ejecta dominated

Triangular hole
– X-ray absorption
– Approx. 450 solar mass cloud
– On near side

No PSR or PWN
– LX < 4x1034 erg s-1
Warren, Hughes, & Slane, ApJ, in press (20 Jan 2003)
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N49B

Middle-aged SNR
– 80” (19 pc) in radius
– 5000-10,000 yrs old
– Near N49

Bright and faint rims
– LMC composition
– Varying ISM density

No PSR or PWN
– LX < 3x1034 erg s-1
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Magnesium-rich ejecta
– Equivalent-width maps
– No O or Ne enhancement
Park, Hughes, Slane, et al. ApJ, in prep.
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SNR 0103-72.6

Middle-aged SNR
– 87” (25 pc) in radius
– >10,000 yrs old (??)
– 2nd brightest SMC SNR

No PSR or PWN
– LX < 4x1034 erg s-1

Circular outer shock
– Low SMC-type abundances
– Why so circular?

Central excess
– Apparently O, Ne, Mg rich
ejecta
Park, Hughes, et al., ApJ, in prep.
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THE END
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