Asymmetries of Heavy Elements in the Young Supernova Remnant Cassiopeia A

Abstract

Supernova remnants (SNRs) offer the means to study supernovae (SNe) long after the original explosion and can provide a unique insight into the mechanism that governs these energetic events. In this work, we examine the X-ray morphologies of different elements from oxygen to iron found in the youngest known core-collapse (CC) SNR in the Milky Way, Cassiopeia A. The heaviest elements exhibit the highest levels of asymmetry, which we relate to the burning process that created the elements and their proximity to the center of explosion. Our findings support recent model predictions that the material closest to the source of explosion will reflect the asymmetries inherent to the SN mechanism. Additionally, we find that the heaviest elements are moving more directly opposed to the neutron star (NS) than the lighter elements. This result is consistent with NS kicks arising from ejecta asymmetries.

Three-dimensional morphological asymmetries in the ejecta of Cassiopeia A using a component separation method in X-rays

“…An accurate mapping of the different elements' distributions, the quantification of their relative asymmetries, and their relation to the NS motion would, for example, allow us to probe the simulation predictions that heavier elements are ejected more asymmetrically and more directly opposed to the NS motion than lighter elements (Wongwathanarat et al 2013;Janka 2017;Gessner & Janka 2018;Müller et al 2019). On this topic, this paper can be viewed as a follow-up to Holland-Ashford et al (2020), a study that aimed to quantitatively compare the relative asymmetries of different elements within Cas A, but A&A 646, A82 (2021) which was hindered due to difficulties in separating and limiting contamination in the elements' distribution. Moreover, in that analysis, the separation of the blue-and red-shifted parts in these distributions was not possible.…”

“…Specifically, the GMCA is able to disentangle detailed maps of a red-and a blue-shifted parts in the distributions of Si, S, Ca, Ar, and Fe, thus providing new and crucial information about the three-dimensional morphology of Cas A. This is a step forward as previous studies intending to map the distribution of the individual elements and study their asymmetries in Cas A in X-rays (Hwang & Laming 2012;Katsuda et al 2018;Holland-Ashford et al 2020) were not able to separate red-and blue-shifted components.…”

Three-dimensional morphological asymmetries in the ejecta of Cassiopeia A using a component separation method in X-rays

“…An accurate mapping of the different elements' distributions, the quantification of their relative asymmetries, and their relation to the NS motion would, for example, allow us to probe the simulation predictions that heavier elements are ejected more asymmetrically and more directly opposed to the NS motion than lighter elements (Wongwathanarat et al 2013;Janka 2017;Gessner & Janka 2018;Müller et al 2019). On this topic, this paper can be viewed as a follow-up to Holland-Ashford et al (2020), a study that aimed to quantitatively compare the relative asymmetries of different elements within Cas A, but which was hindered due to difficulties in separating and limiting contamination in the elements' distribution. Moreover, in that analysis, the separation of the blue-and red-shifted parts in these distributions was not possible.…”

“…Specifically, the GMCA is able to disentangle detailed maps of a red-and a blue-shifted parts in the distributions of Si, S, Ca, Ar, and Fe, thus providing new and crucial information about the three-dimensional morphology of Cas A. This is a step forward as previous studies intending to map the distribution of the individual elements and study their asymmetries in Cas A in X-rays (Hwang & Laming 2012;Katsuda et al 2018;Holland-Ashford et al 2020) were not able to separate red-and blue-shifted components. This paper is structured as follows.…”

Discovery of Stable Titanium at the Northeastern Jet of Cassiopeia A: Need for a Weak Jet Mechanism?

“…Recent simulations of the neutrino-driven explosion that is a currently viable mechanism (Bethe & Wilson 1985) have indicated that the SN shock wave can be accelerated mainly by convective hot bubbles produced by neutrino heating and standing accretion shock instability: SASI (Janka 2012;Burrows & Vartanyan 2021). These effects could be related to the observed asymmetric ejecta distributions and neutron-star kick directions of CC remnants (Lopez et al 2011;Holland-Ashford et al 2017;Holland-Ashford et al 2020;Katsuda et al 2018). In addition to this mechanism, bipolar explosions that could originate from the rotation of the progenitor star are also believed to be an important asymmetric mechanism to explain SN/SNR observations (Khokhlov et al 1999;Fryer & Heger 2000;Takiwaki et al 2009).…”