X-Raying%20the%20Hot%20Universe

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X-Ray Studies of Nucleosynthesis and Abundances
in Supernova Remnants John P. Hughes Rutgers
University
2
Why X-rays?

• Lya lines of all species from C (0.368 keV) to Zn
  (9.3 keV)
• kT 106 K to 108 K from shocks in ejecta and
  CSM/ISM

W49B
ASCA
S
Si
Ar
Ca
Fe
3
X-ray Emission/Atomic Processes
Continuum emission thermal bremsstrahlung
Line emission
Abundance of element Z
Ionization fraction of ion i
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Abundance Determination Issues

• Thermodynamic State
• Nonequilibrium Ionization (NEI) (net105 cm-3 yr)
• T, n evolution with time/radius (e.g., Sedov)
• Other effects
• Heating/cooling in pure element ejecta
• Te/Tp
• Nonthermal particles (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 (MD5/2)
• 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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Where do we find ejecta?

• Optical SNRs with high velocity oxygen-rich
  features
• Galactic Cas A, G292.01.8, 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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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

• 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
• Explosive nucleosynthesis
• Some mechanism drives a shock wave with 1051 erg
  through the Fe-core
• Burning front Ts of 109 K cause explosive O-
  and Si-burning
• 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 O, Si, S, Ar, Ca
Explosive Ne/C-burning 1.2 O, Mg, Si, Ne
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Overturning Our View of Cas A
Hughes, Rakowski, Burrows, and Slane 2000, ApJL,
528, L109.
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Cas A - Doppler Imaging by XMM

• Similar velocity structures in different lines
• SE knots blueshifted
• N knots redshifted
• Tight correlation between Si and S velocities
• Fe
• Note velocity distribution in N
• Extends to more positive velocities than Si or S

Willingale et al 2002, AA, 381, 1039
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Cas A 3D Ejecta Model
Plane of the sky
Rotated
Red Si Ka Green S Ka Blue Fe Ka Circle Main
shock
Fe-rich ejecta lies outside Si/S-rich ejecta
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Oxygen-Rich SNR G292.01.8
Park et al 2001, ApJL, 564, L39
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Oxygen-Rich SNR G292.01.8
Ejecta Rich in O, Ne, and Mg, some Si O/Ne lt
1 No Si-rich or Fe-rich ejecta
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Oxygen-Rich SNR G292.01.8
Normal Composition, CSM Central bright bar an
axisymmetric stellar wind (Blondin et al
1996) Thin, circumferential filaments enclose
ejecta-dominated material red/blue supergiant
wind boundary
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Thermonuclear Supernovae

• 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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Identifying Remnants of SN Ia

• Balmer-dominated SNRs (partially neutral ISM)
• Ejecta abundances (Si and Fe rich, poor in O and
  Ne)
• Remnant structure (uniform ISM, smoother
  ejecta, little spectral variation)

Tycho
E0509-67.5
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SN Ia Spectra and Abundances

• Comparison to models
• O, Ne, Mg relatively low
• Si, S, Ar, Ca consistent
• Fe very low (lt0.1)
• Other spectral results
• Fe co-spatial with Si, but hotter and lower net

W7 Nomoto et al 1984, Thielemann et al
1993 WDD1 Iwamoto et al 1999 NEI fit Warren et
al 2003
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ISM Abundances of the LMC

• Using SNRs as a probe of the ISM
• 7 SNRs, ages from 2,000 yr to 20,000 yr
• Data from ASCA
• Spectra calculated for evolutionary models (Sedov
  solution)
• spatial variation
• temporal variation

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LMC SNRs Integrated Abundances
From fits to ASCA global X-ray spectra of 7
evolved LMC remnants
N49B
DEM L71
Hughes, Hayashi, Koyama 1998, ApJ, 505, 732
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LMC Metal Abundances
Species HHK98 Duf84 RD92
O 8.21(7) 8.43(8) 8.35(6)
Ne 7.55(8) 7.64(10) 7.61(5)
Mg 7.08(7) . . . 7.47(13)
Si 7.04(8) . . . 7.8
S 6.77(13) 6.85(11) 6.70(9)
Fe 7.01(11) . . . 7.23(14)
HHK95 ASCA X-ray SNRs Duf84 UV/Optical
spectra H II regions (Dufour 1984) RD92 F
supergiants (Mg, Si, Fe) (Russell Bessel 1989)
H II regions, SNRs (O, Ne, S) (Russell
Dopita 1990)
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DEM L71

• Middle-aged SNR
• 36 (8.7 pc) in radius
• 4,000 yrs old
• Rims LMC composition
• Core Fe/O gt 5 times solar
• Ejecta mass 1.5 Msun

SN Ia ejecta
Hughes, Ghavamian, Rakowski, Slane 2003, ApJ,
582, L95
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N49B

• Middle-aged SNR
• 80 (19 pc) in radius
• 5000-10,000 yrs old
• Bright and faint rims
• LMC composition
• ISM density varies by x10
• Ejecta
• Revealed by equivalent-width maps
• Mg Si rich, no strong O or Ne

Park, Hughes, Slane, Burrows, Garmire, Nousek
2003, ApJ, submitted.
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SNR 0103-72.6

• Middle-aged SNR
• 87 (25 pc) in radius
• gt10,000 yrs old (?)
• Circular rim
• SMC composition
• Central bright region
• O, Ne, Mg, Si-rich ejecta
• No Fe enhancement

Park, et al 2003, ApJ, in prep.
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Summary

• Core Collapse SNe
• Cas A
• X-ray ejecta dominated by Si, S, and Fe
• explosive nucleosynthesis
• Extensive mixing and overturning of ejecta layers
• G292.01.8
• X-ray ejecta dominated by O, Ne, and Mg (no Fe)
• Ambient medium strongly modified by progenitor
• Contains normal young pulsar and its wind
  nebula

Highly Structured Ejecta/Environment
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Summary

• Thermonuclear SNe (Tycho, E0509-67.5)
• X-ray ejecta dominated by Si, S, and Fe
• Stratification (most of the Fe core unshocked)
• Fe higher kT, lower net due to
• evolution (ejecta density profile)
• radioactivity
• Ejecta relatively smooth and symmetric
• only factor of 2 intensity variations
• little spectral variation
• few (one or two) clumps of Fe-rich ejecta

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Summary

• Evolved LMC SNRs
• Global X-ray abundances consistent with
  optical/UV values
• Individual SNRs show obvious signs of ejecta
• DEM L71 4,000 yrs, Si and Fe-rich SN Ia ejecta
• N49B 5,000-10,000 yrs, Mg and Si-rich ejecta
• E0103-72.6 10,000 yrs, O, Ne, and Mg-rich
  ejecta
• Issues for nucleosynthesis models
• O/Ne ratio lt 1 (G292.01.8)
• O,Ne/Mg ltlt 1 (N49B)

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THE END
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SN Ia Spectra and Abundances
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Properties of DEM L71 Ejecta

• Outer rim lowered abundances, 0.2 solar (LMC
  ISM)
• Core enhanced Fe abundance, Fe/O gt 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 lt 2 Msun

• Main error source of electrons

Fe-rich, low mass SN Ia
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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 lt 4x1034 erg s-1

Warren, Hughes, Slane, ApJ, in press (20 Jan
2003)