Chandra View of
Pulsar Wind Nebulae Torii
submitted to ApJ
Contents:
1. Introduction
2. PWN torus and spin-down luminosity
3. Discussion and application
Aya Bamba
ISAS/JAXA -> DIAS
(Oct.01)
1. Introduction
Chandra discovered torii and jets
of pulsar wind nebulae !!
What is the origin of torus ?
Related to
termination shock of pulsar wind ?
rs =
Edot
4pchPext
1/2
rs: termination shock radius
Edot: spin-down energy c: light speed
h: filling factor Pext: external pressure
Objectives:
To understand the relation
between torus and termination shock.
Correlation between torus radius and spin-down energy ?
2. Correlation between torus and termination shock
2.1. Torus radius
Ng+04, Ng+08
developed the fitting method of
2-dimensional images of PWNe
double torii
Crab
Vela
-> torus information
radius, angle, width, ….
Successfully determined
parameters for ~10 PWNe
Our samples
11 samples from Ng & Romani (04, 08), and Romani+05
The radii are converted to physical size
with the latest distance estimation
2.2. Spin-down energy vs. torus radius
clear correlation with
correlation factor of 0.82
linear fit
-> rejected
due to too small errors
With larger errors
artificial error:
delta(log r) = 0.3
log r = 0.57±0.22 log Edot – 22.3±8.0
3. Discussion (1): The origin of the correlation ?
log r = 0.57±0.22 log Edot – 22.3±8.0
dependency is consistent with the termination shock !
1/2
Edot
rs =
4pchPext
If we assume log r ~ 0.5 log Edot
h
r/rs = 1.9 (1.2-3.0)
1
1/2
Pext
1.6x10-9 [g cm-2s-1]
1/2
(kT=1keV, n=1 cm-3)
Torus radius is roughly same to that of termination shock.
The origin of dispersion of delta (log r) = 0.3
delta (r)
delta (Pext)
~ factor 2
~ 40% dispersion
Naturally explained by the dispersion of the external pressure
Discussion (2): New method for Edot estimation
log r = 0.57±0.22 log Edot – 22.3±8.0
With torus radius, we can estimate Edot
without period and period derivative !
-> good Edot estimator ??
example: G0.9+0.1
One of the bright PWN
No pulsation has been found
In the GC region -> distance known
In the case of G0.9+0.1
Gaensler+01
discovery of small-scale PWN
size: 5” x 8”
-> radius ~ 4 arcsec
= 0.16 pc @ 8.5 kpc
-> Edot = 5.3 x 1037 ergs/s
one of the most energetic pulsar !
Camilo+09 (arxiv: 0906.3289)
discovered pulsation at 2 GHz !
P=52ms, Pdot=1.5557x10-13s/s -> Edot=4.5x1037ergs/s
Our method is valid for G0.9+0.1.
We can try it with DEM L241 (Bamba+06),
HESSJ1813 (Gotthelf+09),…
Summary
Chandra discovered torus structure surrounding pulsars.
The spin-down luminosity and the torus radius have
very strong correlation (corr. factor = 0.82).
The relation can be written as
log r = 0.57±0.22 log Edot – 22.3±8.0
The dispersion of the data set is ~40%
if it is due to the external pressure dispersion.
The relation is a good Edot estimator without P and Pdot.