Supernova Remnants Shell-type versus Crab-like Phases of shell-type

Supernova Remnants  Shell-type versus Crab-like  Phases of shell-type

Supernova Remnants Shell-type versus Crab-like Phases of shell-type SNR Shell-type SNR Shell-type SNR: X-ray, radio, and optical emission come from a shell. Xrays are usually thermal, but can have non-thermal components. Shell is expanding. Power source is inertia left from initial supernova. No

current input of energy. RCW 86, SN in 185 AD Plerions Center filled or Crab-like SNR, or pulsar wind nebulae: X-ray, radio, and optical emission come from a filled, central region. X-rays are nonthermal. Motions can be detected internal to the nebula. Crab, SN in 1054 AD

Continuously powered by relativistic wind from pulsar at center of nebula. Mixed Morphology Plerionic composite: shell-type on the outside, Crab-like at the center. Thermal composite: Radio shell, center-filled X-ray emission, but X-rays are thermal. Thought to occur in denser ISM than shelltype SNR. X-rays may be due to

evaporation of clouds ISM after shock front has passed. W28: red = radio, green = H, blue = X-ray, Phases of Shell-type SNRs Supernova explosion ejecta v ~ 104 km/s Free expansion - ejecta mass > swept up mass

Adiabatic or Sedov swept-up mass > eject mass Snow-plow or Cooling shock front cools, interior also cools Disappearence remnant slows to speed of the random velocities in the surrounding medium, merges with ISM Shock Formation At time t=0, mass m0 of gas is ejected with velocity v0 and total kinetic energy E0. This interacts with surrounding interstellar material with density and low T. Shock front, ahead

of heated material R The shell velocity much higher than the sound speed in ISM, so a shock front of radius R forms. ISM Free Expansion Shell of swept-up material in front of shock does not represent a significant increase in mass of the system.

ISM mass previously within the swept-up sphere of radius R is still small compared to the ejecta mass: (4/3))R3) << m0 Since momentum is conserved: m0v0 = (m0+ (4/3))0R3) )v As long as swept-up mass << ejecta mass, the velocity of the shock front remains constant and Rs(t) ~ v0t The temperature decreases due to adiabatic expansion, T R-3)(-1) Sedov Phase

Dynamics can be described by location of shock front versus time. We look for a self similar solution, in which the dynamics can be reduced to one variable = Rt Note that dynamics are determined by initial energy of explosion, E, and density of ISM, 0. Consider quantity E/0. It has units of (length)5(time)-2. Therefore, (E/0)(t2/R5) is a dimensionless quantity which describes the dynamics of the expansion. The solution requires R(t) = k(E/0)1/5 t2/5 and v(t) = 2R/5t This solution describes the expansion of SNR pretty well. Shock Jump v1

downstream v0 upstream Look at reference frame where shock is stationary, v0 = shock speed Mass flux: 1v1 = 0v0 Momentum flux: P1 + 1v12 = P0 + 0v02 Energy flux: 1v13) + Pv1/(-1) = 0v03) + Pv0/(-1) Where is density, P is pressure, is the adiabatic index. Introduce the Mach number M = v0/c0 where c0 = sqrt(P0/0) is the sound speed upstream, and find in the limit of large M

1/0= (+1)/(-1) and T1/T0 = 2(-1)M2/(+1)2 For = 5/3), find 1/0 = 4 and T1/T0 = (5/16)M2 Get large increase in temperature for large M. Sedov Solution In Sedov solution, find for downstream material: pressure = (3)/4) 0v2 temperature = (3)m/16k) v2 where m is the mean mass per particle downstream (including electrons) and k is Boltzmanns constant. Temperature ~ (10 K)v2 for v in km/s, For v ~ 1000 km/s, have T ~ 107 K which means gas is heated to X-ray producing temperatures.

N132D in the LMC Shock speed ~ 2,000 km/s. Gas is heated by shock to X-ray emitting temperatures. Although gas glows in X-rays, the loss of energy due to radiation is relatively unimportant to the dynamics of the expansion, i.e. cooling time is longer than age of SNR. Radiative Cooling

Eventually, the shock slows down, gas is heated less. Define end of adiabatic phase as when half of energy has been radiated away. Typically, shock speed is then about 200 km/s (with dependence on initial energy and ISM density). Most material swept-up into dense, cool shell. Residual hot gas in interior emits weak X-rays. Matter behind shock cools quickly, pressure is no longer important, shell moves with constant momentum (4/3))R3)0v = constant. 8 t 3) R Rrad

5 t rad 5 1/ 4 Disappearance When shock velocity drop to ~20 km/s, the expansion becomes subsonic and the SNR merges with the ISM. However, the SNR leaves magnetic fields and cosmic rays which can still persist with observable imprints for millions of years.

Phases of Shell-type SNRs Supernova explosion Fast Free expansion - Hundreds of years Adiabatic or Sedov 10,000-20,000 years Snow-plow or Cooling Few 100,000 years Disappearence Up to millions of years

Recently Viewed Presentations

  • Jonah The Prophet - St. Mary, Ottawa

    Jonah The Prophet - St. Mary, Ottawa

    Jonah and the people of Nineveh (Continued) Jonah listens to God and goes to Nineveh to warn them → In 40 days, the city of Nineveh will be destroyed. The people repent and God decides to relent them form the...
  • Jeopardy Review - msinksterteaches.weebly.com

    Jeopardy Review - msinksterteaches.weebly.com

    JEOPARDY GAME RULES FINAL ROUND Other Lands Victorians
  • Chemistry 2: Bonding, Structure and the Properties of

    Chemistry 2: Bonding, Structure and the Properties of

    Property. Reason. 13 High melting point. There is a strong electrostatic force between the positive and negative ions in the giant lattice.A large amount of energy is needed to overcome this force.. 14 Conduct electricity when liquid/ molten. Ions are...
  • Forces - St. Lawrence University

    Forces - St. Lawrence University

    Waves add crest to trough (destructive dark spots) incoming waves. incoming particles. Particles pile up under each slit. Sequence of bright and dark spots. Two bright spots. Light Acts As A Particle. Light pushes dust out of the solar system...
  • FdSc HEALTH & SOCIAL CARE PRACTICE COURSE HANDBOOK

    FdSc HEALTH & SOCIAL CARE PRACTICE COURSE HANDBOOK

    "Iinitially only wanted to do the course to progress onto my nurse training and saw it as a bit of a stepping stone, however one year in, I can honestly say I have learned a lot and my practice has...
  • Microbes&quot;Investigate biological ideas relating to ...

    Microbes"Investigate biological ideas relating to ...

    4°C, 20°C, and 28°C. What difference does Temperature make? ... MRS GREN. processes. Viruses are not really living things at all. They can't move by themselves, they can't reproduce without other cells, they don't respire, or excrete, or feed.
  • Presented to: DoD Composite Maintainers TIM US Army

    Presented to: DoD Composite Maintainers TIM US Army

    In Composite Repair. Thetechnician,whetherinthefield,at depot,orinthefactory,performing the repairisthe"MaterialManufacturer." Thecompetenceofthe technicianhasadirect impact onthestrengthoftherepair and ultimatelyairworthiness.
  • What time is it? - 中国教育和科研计算机网CERNET

    What time is it? - 中国教育和科研计算机网CERNET

    The little hand tells you the ... it is. The BIG hand tells you how many . minutes. after the hour. Some clocks have a second hand, like the red one. ... Draw the hands on the clock for each...