Seminario: presentazione Tesi G. La Malfa (UNIPA)

Speaker: Giorgio La Malfa
Relatore: Marco Miceli
Titolo:Anisotropies in core-collapse supernova explosions: modeling the evolution of a magnetorotational supernova remnant
The core-collapse supernovae (CCSNe) whose explosion is driven by mag-
netorotational instabilities (MRIs) are believed to be viable sources of extremely
interesting astrophysical phenomena, such as hypernovae, super-luminous SNe, magnetars and gamma-ray bursts. Observations of the supernova remnants (SNRs) resulting from these objects pose an important tool for their study. To this end,
numerical simulations offer valuable insights.
Here my goal is to investigate to which extent the supernova remnant (SNR)
of an MR-SN retains memory of the explosion asymmetry, and to study the mor-
phology of the stellar ejecta throughout the evolution.
I performed a three-dimensional (3D) hydrodynamic (HD) simulation of a MR-
SNR, by evolving a state-of-the art MR-SN model available in the literature. The
simulation covers from a few hours after the shock breakout to ∼ 10,000 yrs, with
the adoption of an analytically prescribed circumstellar medium (CSM).
The early outflow jet-like asymmetry, characteristic of MR-SNe, causes the for-
mation of a Mach disk in the equatorial plane. This turns into a torus-like high
pressure region and leads the SNR to a bicone morphology. The pristine bipolar
jet-like structure shows an asymmetry in the ejection time. The simulation indi-
cates that the remnant keeps memory of this asymmetry, presenting a narrower
morphology in the direction of the first ejected jet. The forward shock presents
an elongated morphology, with a polar-to-equatorial ratio of ∼ 1.12 for the first ∼
200 yrs, decaying quite rapidly (down to ∼ 1.06) at ∼ 500 yrs. The stellar ejecta
exhibit a higher ratio of up to 1.20. The ejecta asymmetry increases when they
extend to the forward shock through RT instabilities, deforming the shock since
∼ 200 yrs. A comparison between a proxy of the X-ray emission and an X-ray
Chandra observation of Kes 73 (a SNR hosting a magnetar) indicates some simi-
larities, though a more accurate treatment of the CSM could significantly improve
the agreement with observations.
This first glimpse into the evolution of anisotropies in SNRs originating from
MR-SNe indicates that the SNR keeps memory of the anisotropies in the MR ex-
plosion on a time scale of centuries, rather than millenia.