THE EXPANSION ASYMMETRY AND AGE OF THE CASSIOPEIA A SUPERNOVA REMNANT XinZhou

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

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

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

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 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 Standard pipeline IRAF/STSDAD data reduction Background estimation Background estimation Data obtain:

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

The Morphology: The Morphology:Asymmetry Jet and counter jet gaps

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

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

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

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

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

Age estimates:

1671.8± ± ±0.9 by Thorstensen et al.(2001) used 17 knots ±0.9 by Thorstensen et al.(2001) used 17 knots

Knot deceleration: The least decelerated northwest limb offer sronger upper limits to the age ±18.7 The least decelerated northwest limb offer sronger upper limits to the age ±18.7 The direct interaction with local gas τ drag ~ χ R k /v k ~2000yr The direct interaction with local gas τ drag ~ χ R k /v k ~2000yr τ b ~4χ^1/2 R k /v k ~50yr τ b ~4χ^1/2 R k /v k ~50yr The internal shock driven into the knot The internal shock driven into the knot 30 to 500 km s^-1 30 to 500 km s^-1

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

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

A brief of Light-Echo:

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