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Discovery of Temporal Changes in the Torus around PSR B1509-58

Discovery of Temporal Changes in the Torus around PSR B1509-58. Y. Yatsu, N. Kawai, T. Nakamori, & H. Nakajima Tokyo Institute of Technology. Contents of this talk. Introduction Data Analysis and Results Discussion Conclusion. Temporal studies of PWNe.

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Discovery of Temporal Changes in the Torus around PSR B1509-58

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  1. Discovery of Temporal Changes in the Torus around PSR B1509-58 Y. Yatsu, N. Kawai, T. Nakamori, & H. Nakajima Tokyo Institute of Technology

  2. Contents of this talk • Introduction • Data Analysis and Results • Discussion • Conclusion

  3. Temporal studies of PWNe Providing the information of plasma dynamics directly! We would like to find the temporal changes on the torus of PSR B1509-58 as seen in the Crab nebula.

  4. PSR B1509-58 Young and Energetic Pulsar • D = 5.2 +/- 1.4 kpc • P = 150 ms (tc=1700 yr) • Lspin = 1.8 x 1037 ergs s-1 • Surrounding Radio shell (MSH15-52) PSR B1509-58 10 arcmin We focused on the torus within 30” from the pulsar.

  5. Very fine structures at the pulsar vicinity Outer arc: 30~60” • Nested tori -Inner arc -Outer arc Gaensler et al. +02 DeLaney et al. +06 • Inner ring Yatsu et al. +09 Inner arc: ~30” Inner Ring R~10” South Jet 1 arcmin

  6. Observations We used archive data of four times monitoring observation.

  7. Region selection • In order to investigate the torus, the jet region was excluded. • The funnel were divided into 80 sectors with a width of 0.5”. vflow = c/3 (I = 50deg) Selected region Jet Torus

  8. Variations of radial profile Radial profile We searched moving features by using cross correlation function. Vapp ~ 10.5 arcsec yr -1 (~ 0.86c for D=5.2 kpc) 41 days 81 days Surface Brightness 172 days 0 5 10 15 20 25 30 Distance from the Pulsar [arcsec] We detected moving features on the torus running at 10.5 arcsec/yr outward from the pulsar !

  9. i Calculation of the moving velocity Considering the superluminal motion effect, v ~ 0.65c(30° < i < 50°) is required for vapp = 0.86c. i = 40° i = 50° Apparent Velocity [c] 1.0 Vapp = 0.86c i = 30° Torus 0.8 0.6 0.4 0.2 0 0.2 0.4 0.6 0.8 1.0 Velocity [c]

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

  11. What’s moving? (2) “Propagation of magneto-sonic wave” Velocity of the Fast-mode magneto-sonic wave (Delaney et al. 2006) The Fast mod magneto-sonic wave can explain the observed proper motion.

  12. 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 .

  13. Cross Correlation Function ΔT = 41 day CCF Radial profile 41 days ΔT = 81 day 81 days CCF 172 days ΔT = 122 day Surface Brightness CCF 0 5 10 15 20 25 30 ΔT = 172 day CCF 0 2 4 6 8 10 Travel Distance [arcsec]

  14. Inclination angle vs Flow velocity i = 30° i = 50° i = 40°

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