Discovery of Temporal Changes in the Torus around PSR B1509-58
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Discovery of Temporal Changes in the Torus around PSR B1509-58
Y. Yatsu, N. Kawai, T. Nakamori, & H. Nakajima Tokyo Institute of Technology
2009 July 8th
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Contents of this talk
Introduction
Data Analysis and Results
Discussion
Conclusion
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Temporal studies of PWNe
We would like to find the temporal changes on the torus of PSR B1509-58 as seen in the Crab nebula.
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- Crab nebula (Mori et al. 2004)- Vela Pulsar (Pavlov et al. 2003)- PSR B1509-58 (DeLaney et al. 2006)- G11.2-0.3 (Roberts et al. 2003)- PSR B0540-69 (DeLuca et al. 2007)
Providing the information of plasma dynamics directly!
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PSR B1509-58
Young and Energetic Pulsar
D = 5.2 +/- 1.4 kpc
P = 150 ms (c 1700 yr)
Lspin = 1.8 x 1037 ergs s-1
Surrounding Radio shell (MSH15-52)
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We focused on the torus within 30” from the pulsar.
PSR B1509-58
10 arcmin
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5Very fine structures at the pulsar vicinity
Nested tori-Inner arc-Outer arcGaensler et al. +02DeLaney et al. +06
Inner ringYatsu et al. +09
Outer arc: 30~60”
Inner arc: ~30”
South Jet
Inner Ring R~10”
1 arcmin
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Observations
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We used archive data of
four times monitoring observation.
ObsID Date ExpTime5534 2004,12,28 (T=0) 50 ks
5535 T = 41 days 43 ks
6116 T = 122 days 48 ks
6117 T = 294 days 46 ks
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Region selection
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vflow = c/3
(I = 50deg)
In order to investigate the torus, the jet region was excluded.
The funnel were divided into
80 sectors with a width of 0.5”.
Jet
Torus
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Variations of radial profile
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41 days81 days
172 days
0 5 10 15 20 25 30Distance from the Pulsar [arcsec]
Sur
face
Brig
htne
ss
We searched moving features by using cross correlation function.
We detected moving features on the torusrunning at 10.5 arcsec/yr outward from the pulsar !
Radial profileVapp ~ 10.5 arcsec yr -1
(~ 0.86c for D=5.2 kpc)
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Calculation of the moving velocity
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Considering the superluminal motion effect,
v ~ 0.65c (30° < i < 50°) is required for vapp = 0.86c.
i
Torusi =
40°
0 0.2 0.4 0.6 0.8 1.0Velocity [c]
1.0
0.8
0.6
0.4
0.2
Vapp = 0.86ci =
30°i = 5
0°
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What’s moving? (1)“Actual motion of the pulsar wind”
Based on the brightness distribution of the torus
(Pelling et al. 1987)
Vflow ≤ 0.6c (for i ≥ 30 deg)
From the KC-model ( Kennnel & Coroniti 1984 )…
Vflow = c/3(rTS/r)2 ≤ c/3
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It is difficult to explain the proper motion by the actual flow velocity of the pulsar wind.
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What’s moving? (2)“Propagation of magneto-sonic wave”
Velocity of the Fast-mode magneto-sonic wave
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€
VA =c
1+ 4π (ρc 2 + 4 p)[ ] /B2≈ c1+ (16πU /3B2)
= 0.63c
€ €
VF =VA
2 + cs2
1+ (VA /c)2~ 0.7c
€
cs ≤13
c ~ 0.58c
(Delaney et al. 2006)
The Fast mod magneto-sonic wave can explain the observed proper motion.
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Summary
We studied the temporal variation on the torus around PSR B1509-58 using Chandra.
We found temporal changes on the torus propagating at 10.5 arcsec yr -1, analogous to the “moving wisp” as seen in the Crab nebula.
The observed proper motion can be explained by the magnetosonic wave propagating at ~ 0.7c .
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Cross Correlation Function
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CC
FC
CF
41 days81 days
172 days
0 5 10 15 20 25 30
Sur
face
Brig
htne
ss
Radial profile
0 2 4 6 8 10
Travel Distance [arcsec]
CC
F
ΔT = 41 day
ΔT = 81 day
ΔT = 172 day
CC
F ΔT = 122 day
€
CCF(Δr) =E [a(r) − a ]⋅[b(r + Δr) −b ]{ }
σ aσ b
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Inclination angle vs Flow velocity
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i = 30° i = 50°i = 40°