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.

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!

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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Very fine structures at the pulsar vicinity

Nested tori-Inner arc

-Outer arcGaensler et al. +02

DeLaney et al. +06

Inner ringYatsu et al. +09

Outer arc: 30~60”

Inner arc: ~30”

South Jet

Inner Ring R~10”

1 arcmin

Observations

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We used archive data of

four times monitoring observation.

ObsID Date ExpTime

5534 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

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

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 torus

running at 10.5 arcsec/yr outward from the pulsar !

We detected moving features on the torus

running at 10.5 arcsec/yr outward from the pulsar !

Radial profileVapp ~ 10.5 arcsec yr -1

(~ 0.86c for D=5.2 kpc)

Vapp ~ 10.5 arcsec yr -1

(~ 0.86c for D=5.2 kpc)

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

Torus

i = 4

0°

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°

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.

It is difficult to explain the proper motion by the actual flow velocity of the pulsar wind.

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≈

c

1+ (16πU /3B2)= 0.63c

€ €

VF =VA

2 + cs2

1+ (VA /c)2~ 0.7c

€

cs ≤1

3c ~ 0.58c

(Delaney et al. 2006)

The Fast mod magneto-sonic wave can explain the observed proper motion.

The Fast mod magneto-sonic wave can explain the observed proper motion.

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

Inclination angle vs Flow velocity

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i = 30° i = 50°i = 40°