⁴⁴Ti ejecta in young supernova remnants

Abstract

Context. Tracing unstable isotopes produced in supernova nucleosynthesis provides a direct diagnostic of supernova explosion physics. Theoretical models predict an extensive variety of scenarios, which can be constrained through observations of the abundant isotopes 56Ni and 44Ti. Direct evidence of the latter was previously found only in two core-collapse supernova events, and appears to be absent in thermonuclear supernovae. Aims. We aim to to constrain the supernova progenitor types of Cassiopeia A, SN 1987A, Vela Jr., G1.9+0.3, SN1572, and SN1604 through their 44Ti ejecta masses and explosion kinematics. Methods. We analyzed INTEGRAL/SPI observations of the candidate sources utilizing an empirically motivated high-precision background model. We analyzed the three dominant spectroscopically resolved de-excitation lines at 68, 78, and 1157 keV emitted in the decay chain of 44Ti→44Sc→44Ca. The fluxes allow the determination of the production yields of 44Ti. Remnant kinematics were obtained from the Doppler characteristics of the lines. Results. We find a significant signal for Cassiopeia A in all three lines with a combined significance of 5.4σ. The fluxes are (3.3 ± 0.9) × 10−5 ph cm−2 s−1, and (4.2 ± 1.0) × 10−5 ph cm−2 s−1 for the 44Ti and 44Sc decay, respectively. This corresponds to a mass of (2.4 ± 0.7) × 10−4 M⊙ and (3.1 ± 0.8) × 10−4 M⊙, respectively. We obtain higher fluxes for 44Ti with our analysis of Cassiopeia A than were obtained in previous analyses. We discuss potential differences. We interpret the line width from Doppler broadening as expansion velocity of (6400 ± 1900) km s−1. We do not find any significant signal for any other candidate sources. Conclusions. We obtain a high 44Ti ejecta mass for Cassiopeia A that is in disagreement with ejecta yields from symmetric 2D models. Upper limits for the other core-collapse supernovae are in agreement with model predictions and previous studies. The upper limits we find for the three thermonuclear supernovae (G1.9+0.3, SN1572 and SN1604) consistently exclude the double detonation and pure helium deflagration models as progenitors.

Hoinga: a supernova remnant discovered in the SRG/eROSITA All-Sky Survey eRASS1

“…• 2 radius with a constant surface brightness. A detailed description of SPI analysis and robust background modelling can be found in Diehl et al (2018), Siegert et al (2019) and Weinberger et al (2020).…”

From Supernova to Supernova Remnant: The Three-dimensional Imprint of a Thermonuclear Explosion

“…Effects related to 56 Ni will be the strongest in the first few years, and terminated within a hundred years (so well within the ejecta-dominated phase). Another radioactive element of interest if 44 Ti, the mass yields and energy deposits are very small, of the order of respectively 10 −8 M and 10 44 erg, but with a much longer life-time of about 60 yr. Detecting 44 Ti in young Type Ia SNRs has been a longstanding objective of hard X-ray / soft γ-ray missions, see Weinberger et al (2020) and references therein for Tycho and Kepler SNRs.…”

Type Ia Supernova Models: Asymmetric Remnants and Supernova Remnant G1.9+0.3

“…In particular the high-velocity Fe required is difficult to produce unless progenitors possess a high-mass He layer, as in some double-detonation models (e.g., Woosley & Weaver 1994;Sim et al 2012). However, these models also produce amounts of 44 Ti in conflict with observations (Borkowski et al 2010;Weinberger et al 2020).…”