In a paper published in The Astrophysical Journal Letters, researchers studied the Parker's Star Nebula 30 (Pa 30) nebula, the type Iax supernova remnant associated with supernova 1181 (SN 1181). It revealed unique characteristics such as a complex filamentary morphology and a hot, oxygen-rich stellar remnant at its centre.
Study: Expansion Properties of the Young Supernova Type Iax Remnant Pa 30 Revealed. Image Credit: Nazarii_Neshcherenskyi/Shutterstock.com
Integral Field Unit observations showed ejecta moving close to free-expansion velocities and a large inner cavity with a sharply defined edge. The findings indicated an asymmetric explosion and confirmed Pa 30’s origin in the failed thermonuclear explosion of a near- or super-Chandrasekhar white dwarf.
Related Work
Past work on the Pa 30 nebula, identified in 2013 in the National Aeronautics and Space Administration (NASA)'s wide-field Infrared Survey Explorer (WISE) archive, linked to the 1181 AD SN 1181. The nebula's unique morphology includes radial filaments and a central star with extreme velocities, suggesting a failed thermonuclear runaway in a white dwarf. Studies indicate that Pa 30 could result from a double-degenerate white dwarf merger, with its filamentary structure likely formed by Rayleigh–Taylor instability. Infrared and X-ray observations reveal the nebula's complex composition and the interactions between the supernova ejecta and the circumstellar medium.
Keck Telescope Observations Summary
Observations were made using the blue and red arms of the Keck Cosmic Web Imager (KCWI) on the Keck II Telescope at Maunakea. Blue and red low-dispersion gratings (BL and RL) with the medium slicer provided a field of view, spatial resolution, and spectral resolutions for both blue and red arms. A detector binning of 2 × 2 was used, with exposure times including separate exposures for KCWI-blue and KCWI-red and additional exposure for the central star to avoid saturation.
Velocity Mapping and Deprojection Analysis
The study presents the filamentary structure of the Pa 30 nebula, identified through the KCWI-red data cubes, covering the emission from the [S ii] doublet between 6680–6750 Å. The analysis reveals that while the KCWI-red data aligns with the bright filaments observed in previous narrowband imaging, it also uncovers fainter features, suggesting a higher filling factor. The study further extends the detection to other emission lines, with a focus on the velocity structure of the nebula derived from the [S ii] lines. A more comprehensive analysis of the entire dataset is planned for future work.
The Doppler shift of the [S ii] doublet was analysed across the filaments to map the nebula's velocity. By concentrating on the brightest filaments, the team performed Gaussian fitting to determine the line-of-sight velocities. The study identified cases where multiple velocity components existed within a single pixel due to overlapping filaments. A statistical analysis using the 2D Kolmogorov–Smirnov (KS) test revealed no significant spatial correlation between the redshifted and blueshifted components. This suggests that the blue- and redshifted emissions are not significantly correlated spatially.
Regarding deprojection, the study provides a three-dimensional reconstruction of the nebula if the velocities have remained constant since the material was ejected in 1181. The reconstruction shows that the nebula's structure appears nearly spherical, with a noticeable cavity near the central star. Minor discrepancies in the redshifted region are attributed to contamination from a stationary skyline, but these do not impact the overall analysis. NASA's imaging systems contributed to the detailed capture of the nebula's structure, further enhancing the study's observations.
The study examined how deviations from a ballistic ejection model impact the nebula's spatial structure, finding that the ejecta velocities are close to ballistic free-expansion speeds. NASA's advanced modelling techniques accurately estimated these velocities, indicating minimal external influences on the nebula's expansion. Finally, an elliptical regression was performed further to constrain the parameters of the nebula's structure.
The fitted ellipse estimated the ballistic fraction and confirmed that the nebula's age and ejection time are consistent with the historical supernova event in 1181. This result reinforces the assumption that the ejecta from the supernova has not been significantly decelerated or accelerated, supporting the idea that the nebula is indeed the remnant of a historical supernova event, as NASA's extensive observational tools continue to provide valuable insights into such phenomena.
Conclusion
To sum up, the analysis of Pa 30's velocity structure confirms that the nebula is a remnant of the 1181 supernova, with velocities in the ejecta nearly ballistic. NASA's observations reveal a strong flux asymmetry and a large cavity in the remnant, providing evidence for an asymmetric explosion.
The ballistic fraction and the position of the reverse shock further support the hypothesis of a low-density circumstellar medium. Future NASA observations with broader coverage will help refine these findings and provide critical insights into the nebula's dynamical models.
Journal Reference
Cunningham, T. et al. (2024). Expansion Properties of the Young Supernova Type Iax Remnant Pa 30 Revealed. The Astrophysical Journal Letters, 975:1, L7. DOI: 10.3847/2041-8213/ad713b, https://iopscience.iop.org/article/10.3847/2041-8213/ad713b
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