Measurement of the X-ray proper motion in the eastern limb of Puppis A by Chandra X-ray Observatory
Abstract
Massive stars explode at the final stage of evolution and blow off the outer layer of the star strongly. The strong shock wave heats the surrounding interstellar matter to a high temperature, forming a "supernova remnant". The shock velocity is important for exploring the basic parameters of supernova remnants, such as distance, surrounding density, and age, and the electron-ion heating process in collisionless shock waves. Chandra X-ray Observatory, which was launched by NASA in 1999, has an excellent angular resolution of 0.5 arcsec, which corresponds to 1.5\times10$^{11}$ km at $D$=2 kpc. Therefore, this imaging capability enables us to perform precise direct measurements of the shock velocity by multiple X-ray images in difference epochs. Puppis A is one of the brightest supernova remnants in X-rays. It was estimated to have exploded about 4000 years ago and is now extended to about 50 arcmin in angular diameter. Many observations have been carried out over a wide range of wavelengths from radio waves to $\gamma$-rays, but its shock velocity has not been measured directly. The eastern limb of Puppis A was observed by Chandra in 2001. Therefore, we performed the second-epoch observation of the same region in 2016 and compared the X-ray images obtained from both observations, and measured the proper motion. We obtained the proper motion to be 0.016$\pm$0.007 arcsec/yr in the brightest region in the eastern limb. Converting this to a shock velocity, we obtained $V_{sh}$=170$\pm$70 ($D$/2.2 kpc)($\mu$/0.016 arcsec/yr) km/s. On the other hand, according to past X-ray spectral analysis, the electron temperature in this region is 0.3 keV (Hwang et al. 2005), which, combined with the Rankine-Hugoniot relation, suggests a shock velocity of 500 km/s. This is about three times higher than our measurement. In this presentation, we will discuss the cause of this discrepancy, as well as the spatial variation of the shock velocity at the eastern limb and its relationship with the temperature structure that we derived from our spectral analysis.
- Publication:
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43rd COSPAR Scientific Assembly. Held 28 January - 4 February
- Pub Date:
- January 2021
- Bibcode:
- 2021cosp...43E1462I