Chandra Observations of Xray Emission from Supernova Remnants

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gt95 of the mass in this picture
and gt99.999 of this
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.arises in..
Supernovae

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Outline of presentation

• Stars
• Supernovae
• What can we learn from X-rays?
• Some current research
• Some research with Olin partners

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The Classification of Stars
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Why are supernovae interesting?

• They are the source of all elements in the
  universe (except H, He, Li)
• They influence the dynamics of interstellar gas
  and, hence, regulate star formation
• They produce extreme physical systems neutron
  stars, black holes, gamma ray bursts

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APPARENT MAGNITUDEApparent magnitude is a
measure of the brightness of a celestial object
as seen from Earth. The lower the number, the
brighter the object. Negative numbers indicate
extreme brightness. The full moon has an apparent
magnitude of -12.6 the sun's is -26.8. We can
see objects up to 6th magnitude without a
telescope. Apparent magnitude is abbreviated m.
This system of rating the brightness of celestial
objects was developed by the Greek astronomer
Hipparchus in 120 B.C.
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Type I and Type II Supernovae
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Topology of a Supernova Remnant 1051 ergs
kinetic energy release per explosion
Forward Shock into Interstellar Medium
Shocked ISM
Contact Discontinuity (Interface between shocked
ISM and Ejecta)
Unshocked Ejecta
Shocked Ejecta
Reverse Shock into Ejecta
Shocked ISM
Shock velocities?104 km/s, kT3/16 mv2,
Tp2x108 K , Te105 K
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Shocks
occur when v gt cs
We can estimate cs dimensionally
v
On a string, cs f ?
Tension (ML/T2)
Mass density (M/L)
v
p
v
kT
In a gas, cs

km/s in ISM
?
mp
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Supernovae

• Type II (Ib/Ic)
• Fe core collapse in a massive star
• O, Ne, and others
• Neutron star or black hole stellar remnant
• e.g., Cas A, Crab nebula, SN1987A

• Type Ia
• Thermonuclear instability in white dwarf binary
• Fe group, plus others
• No compact stellar remnant
• after explosion
• e.g., Tychos SNR, SN 1006

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Cassiopeia A in the Optical
and the X-Ray Bands
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Combined Imaging and Spectroscopy

• Neutron star (or black hole) remnants of massive
  supernovae
• Separating the forward and reverse shock emission
  components
• Distribution and spectra of the stellar debris
  (ejecta)

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The Crab Nebula
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ASCA (Holt et al. 1994) 1 res
Chandra 0.5 res
ROSAT HRI 5 res
Cassiopeia A
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Cassiopeia A Point Source

• Chandra first light reveals point source
  (Tananbaum 1999)
• No confirmed pulsations (Chakrabarty et al. 2001,
  Murray et al. 2002)
• Not a conventional pulsar
• Hot spots on neutron star? (Pavlov et al. 2000)
  Accretion? Similar to anomalous X-ray pulsars?
  (Chakrabarty et al. 2001)

Crab Nebula Weisskopf et al. 2000
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Cassiopeia A Point Source

• Chandra first light reveals point source
  (Tananbaum 1999)
• No confirmed pulsations (Chakrabarty et al. 2001,
  Murray et al. 2002)
• Not a conventional pulsar
• Hot spots on neutron star? (Pavlov et al. 2000)
  Accretion? Similar to anomalous X-ray pulsars?
  (Chakrabarty et al. 2001)

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Electron Heating at Forward Shock

• X-ray emission from electron collisions,
  sensitive to electron temperature
• Temperature of a particle species behind shock
  proportional to mass kT 3/16 mvs2
• Temperatures equilibrate between species slowly
  by Coulomb collisions
• Possibly faster through plasma processes?

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Oxygen Shock-Heated to kT 0.3 keV
ionized
H-like
He-like
Ionization age
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Energy Selected X-ray Imaging
4-6 keV
Cassiopeia A ACIS spectrum
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Cassiopeia A
Temperatures kT 4-6 keV X-ray expansion 5500
km/s (Vink et al. 1998) 30 keV
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Forward Shock Emission

• Spectra of forward shocks isolated
• Thermal temperatures consistent with Coulomb
  heating of electrons or modest additional heating
• Non-thermal contributions?
  Need more sensitivity at E gt 8 keV
• Possible efficient particle acceleration (lower
  temperature for shock velocity)

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Cassiopeia A Si and S Ejecta
Optical SII
X-ray
Hwang, Holt, Petre (2000)
Fesen Gunderson (1996)
X-ray velocity distribution resembles
optical (Willingale et al. 2001, Hwang et al.
2001, Lawrence et al. 1995)
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Bulk Line-of-Sight Velocities from Doppler Shifts
in Cassiopeia A

• XMM-Newton (top Willingale et al. 2001) and
  Chandra (bottom Hwang et al. 2001) give similar
  patterns for Si also similar to optically
  emitting S ejecta (Lawrence et al. 1995)
• X-ray velocities 2500 km/s optical 4000-6000
  km/s
• XMM-Newton gives pattern for Doppler shifts for
  Fe K similar to Si

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Broadband
Si
Ca
Fe K
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Cassiopeia A Si and Fe Ejecta
Si
Fe K
Si Image Fe Contours
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Cassiopeia A Explosive Nucleosynthesis (Hughes
et al. 2000)
O-burning
Incomplete Si
.. plus Fe
Featureless
Chandra First Light
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Cassiopeia A Knots
Fe L Si S Fe K
Ejecta knots of different composition from
different burning layers (Hughes et al.
2000) Similar Si and Fe temperatures, different
shock times and densities
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Cassiopeia A Ejecta Knots

• Temperatures are comparable 2 keV
• Si-rich knots have low ionization age (electron
  density x time)
• Fe-rich knots have ionization ages that are
  higher by 50-100

Ar
Si
S
Ca
Ar
Fe L
Fe K
Si
S
Ca
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Tychos SNR, Chandra ACIS-S3
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Tychos SNR
Temperatures kT 2.5 keV X-ray expansion 4500
km/s (Hughes 2000) 25 keV
Si and S ejecta
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Nonthermal X-rays from SN 1006
Featureless X-ray spectrum electron synchrotron
radiation (Allen et al. 1997, Koyama et al. 1995,
Reynolds 1996) TeV emission confirmed (Tanimori
et al. 1998) Thermal emission from interior
ASCA (0.5-10 keV)
(Dyer et al. 2001)
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Fe L
Si
S
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Tychos SNR Si and Fe

• Fe K EW image
• Contours show Si EW peaks exterior to Fe K
• Previously noted with ASCA (Hwang Gotthelf
  1997) and
• XMM-Newton (Decourchelle et al. 2001)
• Temperature (and ionization age structure) behind
  reverse shock
• Si ejecta have kT 1 keV,
• too low to excite Fe K emission

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Summary of New Results Cas A Tycho
Outer shock
4500 km/s
5500 km/s
Te 0.1 Tp
non-thermal component
ragged-edged
smooth
asymmetrical
symmetrical
Fe-poor jet
no jet
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Summary of New Results Cas A Tycho
Ejecta
fluffy clumps
dense knots
asymmetrical
symmetrical

near reverse shock
reaching outer shock
Fe/Si, nt incr w/radius
Fe interior to Si
X-ray velocities typically half optical