A New Study on a Type Iax Stellar Remnant and its Probable Association with SN 1181

Abstract

We report observations and modeling of the stellar remnant and presumed double-degenerate merger of Type Iax supernova Pa 30, which is the probable remnant of SN 1181 AD. It is the only known bound stellar SN remnant and the only star with Wolf–Rayet features that is neither a planetary nebula central star nor a massive Population I progenitor. We model the unique emission-line spectrum with broad, strong O vi and O viii lines as a fast stellar wind and shocked, hot gas. Non-LTE wind modeling indicates a mass-loss rate of ∼10−6 M ⊙ yr−1 and a terminal velocity of ∼15,000 km s−1, consistent with earlier results. O viii lines indicate shocked gas temperatures of T ≃ 4 MK. We derive a magnetic field upper limit of B < 2.5 MG, below earlier suggestions. The luminosity indicates a remnant mass of 1.0–1.65 M ⊙ with ejecta mass 0.15 ± 0.05 M ⊙. Archival photometry suggests the stellar remnant has dimmed by ∼0.5 mag over 100 yr. A low Ne/O < 0.15 argues against an O-Ne white dwarf in the merger. A cold dust shell is only the second detection of dust in an SN Iax and the first of cold dust. Our ejecta mass and kinetic energy estimates of the remnant are consistent with Type Iax extragalactic sources.

Discovery of an Exceptional Optical Nebulosity in the Suspected Galactic SN Iax Remnant Pa 30 Linked to the Historical Guest Star of 1181 CE

“…The remnant's hot central star, called J005311 based on its J2000 coordinates (α = 00 h 53 m 11 2, δ = 67 30 2. 4 +  ¢  ), has been proposed to be a high-mass white dwarf (WD), a super-Chandrasekhar-mass WD, or the result of a double-degenerate merger that resulted in an SN Iax explosion (Gvaramadze et al 2019;Kashiyama et al 2019;Oskinova et al 2020;Lykou et al 2023). While the convergence point of the remnant's filaments lies very close to Pa 30ʼs hot central star, some filaments do not appear in perfect alignment with the star's current position.…”

“…A newly recognized Galactic nebula, Pa 30 (G123.1+4.6), located not far from 3C 58 and actually nearer the spot cited by Chinese and Japanese observers, has recently been identified as the likely true remnant of SN 1181 (Ritter et al 2021;Lykou et al 2023;Schaefer 2023). Initially identified as a possible planetary nebula (PN; Patchick candidate number 30), it was subsequently found associated with a very hot star (∼210,000 K) with an astounding 16,000 km s −1 velocity wind (Gvaramadze et al 2019;Garnavich et al 2020).…”

“…The Pa 30 remnant is bright in the mid-infrared (Gvaramadze et al 2019;Ritter et al 2021) and has been detected in X-rays (Oskinova et al 2020). But no associated Hα emission has been firmly detected (Gvaramadze et al 2019;Lykou et al 2023). Deep [O III] λ5007 line-emission images revealed a faint and diffuse emission nebula (Kronberger et al 2014;Ritter et al 2021) while spectra show [S II] λλ 6716, 6731 emission with an expansion velocity ≈1100 km s −1 (Ritter et al 2021).…”

“…Initially identified as a possible planetary nebula (PN; Patchick candidate number 30), it was subsequently found associated with a very hot star (∼210,000 K) with an astounding 16,000 km s −1 velocity wind (Gvaramadze et al 2019;Garnavich et al 2020). A young SNR with a hot surviving compact object suggests that it may be the remnant of a double-degenerate merger leading to a subtype SN Ia known as an SN Iax (Gvaramadze et al 2019;Kashiyama et al 2019;Oskinova et al 2020;Ritter et al 2021;Lykou et al 2023).…”

“…Deep [O III] λ5007 line-emission images revealed a faint and diffuse emission nebula (Kronberger et al 2014;Ritter et al 2021) while spectra show [S II] λλ 6716, 6731 emission with an expansion velocity ≈1100 km s −1 (Ritter et al 2021). Because of its known [S II] emission and a high estimated interstellar extinction (E(B − V ) ; 0.88; Ritter et al 2021;Lykou et al 2023), we thought it worthwhile to explore the optical structure of this young and nearby suspected SN Iax remnant through red [S II] images.…”