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THE EXPANSION ASYMMETRY AND AGE OF THE CASSIOPEIA A SUPERNOVA REMNANT

THE EXPANSION ASYMMETRY AND AGE OF THE CASSIOPEIA A SUPERNOVA REMNANT. XinZhou 2006.06.12. Cas A Introduction Data obtain Morphology Abnormal chemical distribution Asymmetry Motion of central X-ray point source Age estimates Addition- Light-echo of the SNR. Cas A Introduction:.

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THE EXPANSION ASYMMETRY AND AGE OF THE CASSIOPEIA A SUPERNOVA REMNANT

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  1. THE EXPANSION ASYMMETRY AND AGE OF THE CASSIOPEIA A SUPERNOVA REMNANT XinZhou 2006.06.12

  2. Cas A Introduction • Data obtain • Morphology • Abnormal chemical distribution • Asymmetry • Motion of central X-ray point source • Age estimates • Addition- Light-echo of the SNR

  3. Cas A Introduction: • ~325 yrs old,the youngest known Galactic core-collapse remnant • ~3.4 kpc(~11000 ly) differs from the former ~2.8 kpc • Well defined radio and x-ray region ~2’’ • Erupted again about 50 yrs ago

  4. Infra-red warm dust ~10^2K(Spitzer,24-micron) • Optical hot gases ~10^4K(HST,900nm) • X-ray very hot gaes~10^7K and neutron star in center of the shell(Chandra,broadband)

  5. Data obtain: • Hubble Space Telescope(HST),Wide Field Channel of the Advanced Camera for Surveys(ACS/WFC),4 Sloan Digital Sky Survey(SDSS)filters –just 3 is used • Standard pipeline IRAF/STSDAD data reduction • Background estimation

  6. High-velocity,outer ejecta knots’ defination: • Radial distance exceeded 100’’ from the remnant’s center of expansion • Showed a proper motion >=0’’.35yr^-1

  7. The Morphology: Asymmetry Jet and counter jet gaps

  8. Abnormal chemical distribution: 192 strong [O II] emission fast moving knots(FMK) 444 strong [N II] emission FMK Jets contain the highest velocity [S II]emitting ejecta In the other region,N-rich ejecta represent the highest velocity debris followed by the O-rich ejecta,and then the S-rich knots

  9. Possible reason for asymmetry: • Uneven ejecta decelerations due to local ISM density variations and cavities • Bipolar MHD jets • Mildly asymmetrical neutrino-driven explosions • Nature of the SN explosion engine?

  10. Aspherical core-collapse explosions • Popular ‘collapsar’ GRB model • asymmetrical neutrino-driven model • Models of magnetorotationally induced jets • Rotation axis bounce

  11. Motion of central X-ray source • ~330 km s^-1

  12. Anormolous X-ray pulsars(AXPs),soft gamma-ray repeaters(SGRs)-magnetar model • Wide range of observed ‘kick’ velocities • Misalignment between the progenitor’s spin axis and a NS’s velocity vector

  13. Age estimates:

  14. 1671.8±17.9 • 1671.3±0.9 by Thorstensen et al.(2001) used 17 knots

  15. Knot deceleration: • The least decelerated northwest limb offer sronger upper limits to the age 1680.5±18.7 • The direct interaction with local gas τdrag~ χRk/vk ~2000yr • τb~4χ^1/2 Rk/vk~50yr • The internal shock driven into the knot 30 to 500 km s^-1

  16. Questions even not solved • More than one ejecta streams in both jets • Gaps • The reliability of object choosen

  17. Light-Echo around: a blend of at least two light echoes around

  18. A brief of Light-Echo:

  19. the dust appeared to be moving outward at the speed of light • May help pin down the source and the ambient

  20. Thank you for your attention

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