# Presentation: 154979

## SNR  1013rd X-ray Astronomy schoolWallops Island May 12-16 May

- Ilana HARRUS (USRA/NASA/GSFC)
- Many thanks to:
- Pat Slane (Center for Astrophysics)
- CXC website for their marvelous animations
- Chandra SNR catalogue on-line (aka Fred Seward’s catalogue)

## What are SNRs ? 

- SNRs: SuperNova Remnants are the tracers of explosions from stars reaching the end of their lifes. SNRs also enrich the ISM by dispersing material produced both during the star’s life and at the moment of the SN event.
- How frequent? Estimates varies according to SN types, environment (Galaxy type), ...: About 2 per century for Milky Way (all types)

**Notes:**
2 per century is \tau of 50 (years between burst). 
\tau  is 270 years for LMC/ 1000 years for the SMC/ 

## Why should we (you) care? 

- SNRs are probes both of their progenitor star (and of their pre-supernova life) and of the ISM.
- They are also cosmic accelerators (cosmic rays).
- Birth places of neutron stars and stellar mass black holes.
- They can also be space laboratories for study of  high magnetic fields, shock physics, jets, winds, (PWNe)...

## Slide 4

## Slide 5

-                                    is a lot darker....
- Morphology classification is a zoo
- Spectral classification is a royal mess

- Now the real story....

## Hughes et al. 2000, ApJ, 528, L109

- Park et al. 2002, ApJ, 564, L39

**Notes:**
Type Ia produce mainly Fe -- very low O/Fe ratio. 
Type II produces: mainly 0 -- very high O/Fe ratio

## Slide 8

## Park et al. 2002, ApJ, 564, L39

- Hughes & Slane 2003, ApJ (submitted)

**Notes:**
Very high O-- probably CC-- Confirmed by discovery of a PWN. 
Pulsar (Camillo et al. 2000)-- Confirmed 135 ms pulsations. 
Elongated (jets?)-- 

## Is this 

- Is this
- a SNR?

- NO

- YES

- Shell-like?

- YES

- NO

- NO/?

- NO

- NO

- Mostly Thermal?

- YES

- “Mostly thermal?

- “YES”

- Compact Object?

- Mostly Thermal?

- Pulsar associated?

- YES

- YES

- Mostly Thermal?

- NO

- YES

- YES

- Shell-like?

- NO

- YES

- NO

- NO

-          Why is this such a mess??

- SNR evolution (and their appearance now) depends on many factors:
- Its age
- Its environment (density)
- The total energy of the explosion
- and ... its progenitor star (mass, type of SN associated..)

-  3 phases in SNR’s life.

- Free expansion  (less than 200-300 years)
- Adiabatic or “Taylor-Sedov”  phase  (about 20,000 years)
- Radiative or Snow-plow phase (up to 500,000 years)
-  and then ... Merge with the ISM

-       Free  expansion phase

- Independent of the nature of the SN explosion
- No deceleration
- Evolution only depends on Eo  the initial energy.
- Velocity of ejected shell varies between (7-12) 103 km s-1
- Mass swept-up negligible until Msu ~ Meje ~ 1 M
- ===> Rs = 250 yrs Meje 5/6 n1-1/3 E51-1/2
-  SNR enters then its Adiabatic Phase

## Slide 14

-       Sedov-Taylor phase

- The key word here is SELF SIMILAR *(solutions can be **scaled **from solutions elsewhere)*
- ===> f(r, t) becomes f(r/rref) *f(rref)
- (skipping the equations) ... Et voilà!
-                Rs=12.4 pc (KE51/n1)1/5 t4 2/5
-                t ==390 yr Rs Tmeas-1/2

-       Sedov-Taylor phase

- The Sedov-Taylor phase  is one the most often used in papers about SNRs (that’s because one can get actual physical quantities from measurements).
- In Sedov-Taylor model one expects thermal emission coming from a thin shell behind the blast wave. As the shock expends the pressure drops between the shock wave and the material ejected.
- At one point, “reverse” shock starts propagating ===> will eventually heat the ejecta (also thermal emission).

## Slide 17

-       Radiative phase

- T drops as a steep function of radius
- ===> at some point, T is below Trecomb ~ 1 keV
- Age of SNR when this happens depends on models for cooling functions, explosion energy and density.
- Between 17,000 and 25,000 years (assuming standard Eo and n1)
- Then:   THE END... SNR merges with surrounding medium

-       Why so complicated then??

- Different explosion energy, age, ...
- Different angle of visions
- Amount of material along line of sight is not uniform
- ISM is not homogenous
- Different progenitor histories
- .....

-       First the simplest:

-  Different angle of view:

- Then we may see the SNR “through”  a lot more of absorption.

-       ISM not homogenous

- Several models to explain differences with Sedov-Taylor “shell-like” predictions.

- Several problems with this type of models.

- “Several” clouds evaporating “slowly” behind shock wave (White & Long, 1991)

-       Different progenitors

- Type Ia: thermo-nuclear destruction of an accreting white dwarf. Low O/Fe ratio.
- Type II:Core collapse of massive star. High O/Fe ratio.

**Notes:**
This plot also shows why is it difficult to separate the type spectrally. 

## Hughes et al. 2000, ApJ, 528, L109

- Park et al. 2002, ApJ, 564, L39

**Notes:**
Type Ia produce mainly Fe -- very low O/Fe ratio. 
Type II produces: mainly 0 -- very high O/Fe ratio

-     Pulsar Wind Nebulae (in SNRs)

-  Recent developments (using Chandra) of PWNe studies (particle acceleration, magnetic fields, jets, winds, ...)

## Pulsar Wind Nebulae

- Studies of PWN can yield information on magnetic fields, ....

- With the new data increase from Chandra (and the spatial resolution), it is now possible to start doing statistical analysis.

- Gotthelf 2003

## Slide 26

##        What was not mentioned here: 

-  Non-equilibrium ionization effects
-  Non-thermal emission at the shock wave (SN 1006)
- Accuracy of the spectral diagnostics
- Association of PSR/SNR
- ...

## For more information on SNRs: 

- Books and proceedings:
- “Supernovae and Stellar Wind in the ISM”  T. Lozinskaya
- “ Supernovae and supernova remnants” K. Weiler
- “Neutrons stars in supernova remnants” (proc)-- Slane and Gaenlser (Eds.)
- “Exploring the X-ray Universe” Charles & Seward
- Articles:
- Trimble -- Rev. Mod. Phys.1982 Vol 54, No 4
- McKee -- ApJ 1974188 355
- Chevalier -- ApJ 1974 188 501
- Hamilton, Sarazin & Chevalier  1983 ApJ Supp, 51 115

## Conclusions

- SNRs (and PWNe) are a complicated but important field of study.
- Thanks  to  Chandra (its spatial resolution and its ability to allow for spatially resolved spectroscopy) and XMM-Newton (its large effective area and its ability to collect many more photons.)
- ===>large rethinking of the field is happening now

-   Any questions?