First author: J. M. DerKacy
We present a JWST/MIRI low-resolution mid-infrared (MIR) spectroscopic observation of the normal Type Ia supernova (SN Ia) SN 2021aefx at +323 days past rest-frame B-band maximum light. The spectrum ranges from 4-14 um, and shows many unique qualities including a flat-topped $[Ar III]$ 8.991 um profile, a strongly tilted $[Co III]$ 11.888 um feature, and multiple stable Ni lines. These features provide critical information about the physics of the explosion.
First author: William Sheu
The introduction of deep wide-field surveys in recent years and the adoption of machine learning techniques have led to the discoveries of $\mathcal{O}(10^4)$ strong gravitational lensing systems and candidates. However, the discovery of multiply lensed transients remains a rarity. Lensed transients and especially lensed supernovae are invaluable tools to cosmology as they allow us to constrain cosmological parameters via lens modeling and the measurements of their time delays.
First author: P. F. Velazquez
Thermonuclear and core-collapse supernova remnants (SNRs) are the nebular leftovers of defunct stars. Their morphology and emission properties provide insights into the evolutionary history of the progenitor star. But while some SNRs are spherical, as expected from a point-like explosion expanding into a roughly uniform medium, many others exhibit complex non-spherical morphologies which are often not easily explained. In this work, we use three-dimensional magnetohydrodynamic simulations to show that rectangular and jet-like morphologies can be explained by supernovae (SNe), either type Ia or type II, expanding within anisotropic, bipolar stellar wind bubbles driven by the progenitor star.
First author: Ryo Sawada
Details of the core-collapse supernova (CCSN) explosion mechanism still need to be fully understood. There is an increasing number of successful examples of reproducing explosions in multidimensional hydrodynamic simulations, but subsequent studies pointed out that the growth rates of the explosion energy $\dot{E}\mathrm{expl}$ of these simulations are insufficient to produce enough $^{56}$Ni to match observations. This issue is known as the `$^{56}$Ni problem' in CCSNe. Recently, however, some studies have suggested that this $^{56}$Ni problem is derived from the simplicity of the explosion model.
First author: A. -C. Buellet
The growth of instabilities is key to trigger a supernova explosion during the phase of stalled shock, immediately after the birth of a proto-neutron star (PNS). We assess the effect of stellar rotation on neutrino-driven convection and SASI when neutrino heating is taken into account. Rotation affects the frequency of the mode m=2 detectable with gravitational waves (GW). We use a linear stability analysis in the equatorial plane between the PNS and the stationary shock and consider a large range of specific angular momenta, neutrino luminosities and mass accretion rates.
First author: John Banovetz
We present proper motion measurements of oxygen-rich ejecta of the LMC supernova remnant N132D using two epochs of Hubble Space Telescope Advanced Camera for Surveys data spanning 16 years. The proper motions of 120 individual knots of oxygen-rich gas were measured and used to calculate a center of expansion (CoE) of $\alpha$=05:25:01.71 and $\delta$=-69:38:41.64 (J2000) with a 1-$\sigma$ uncertainty of 2.90 arcseconds. This new CoE measurement is 9.
First author: Chris Nagele
The assembly of supermassive black holes poses a challenge primarily because of observed quasars at high redshift, but additionally because of the current lack of observations of intermediate mass black holes. One plausible scenario for creating supermassive black holes is direct collapse triggered by the merger of two gas rich galaxies. This scenario allows the creation of supermassive stars with up to solar metallicity, where the enhanced metallicity is enabled by extremely rapid accretion.
First author: Felipe M F de Oliveira
Redshift measurement has always been a constant need in modern astronomy and cosmology. And as new surveys have been providing an immense amount of data on astronomical objects, the need to process such data automatically proves to be increasingly necessary. In this article, we use simulated data from the Dark Energy Survey, and from a pipeline originally created to classify supernovae, we developed a linear regression algorithm optimized through novel automated machine learning (AutoML) frameworks achieving an error score better than ordinary data pre-processing methods when compared with other modern algorithms (such as XGBOOST).
First author: Amir Sharon
Calcium-rich supernovae (Ca-rich SNe) are faint, rapidly evolving transients whose progenitor system is yet to be determined. We derive the $\gamma$-ray deposition histories of five Ca-rich SNe from the literature in order to place constraints on possible progenitor systems. We find that the $ \gamma $-ray escape time, $ t_0 $, of the Ca-rich SNe sample is $\approx35$-$65 ,\rm{d}$, within the unoccupied region between Type Ia SNe and stripped envelope supernovae (SESNe).
First author: Jessica A. Cowell
The assumption of isotropy – that the Universe looks the same in all directions on large scales – is fundamental to the standard cosmological model. This model forms the building blocks of essentially all of our cosmological knowledge to date. It is therefore critical to empirically test in which regimes its core assumptions hold. Anisotropies in the cosmic expansion are expected on small scales due to nonlinear structures in the late Universe, however, the extent to which these anisotropies might impact our low-redshift observations remains to be fully tested.
