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Modelling the red–blue asymmetries seen in the broad emission lines of core-collapse supernovae (CCSNe) is a powerful technique to quantify total dust mass formed in the ejecta at late times (>5 yr after outburst) when ejecta dust temperatures become too low to be detected by mid-infrared (IR) instruments. Following our success in using the Monte Carlo radiative transfer code damocles to measure the dust mass evolution in SN 1987A and other CCSNe, we present the most comprehensive sample of dust mass measurements yet made with damocles, for CCSNe aged between 4 and 60 yr after outburst. Our sample comprises multi-epoch late-time optical spectra taken with the Gemini/Gemini Multi-Object Spectrographs (GMOS) and Very Large Telescope (VLT) X-Shooter spectrographs, supplemented by archival spectra. For the 14 CCSNe that we have modelled, we confirm a dust mass growth with time that can be fit by a sigmoid curve that is found to saturate beyond an age of ∼30 yr, at a mass of 0.23$^{+0.17}_{-0.12}$ M⊙. For an expanded sample including dust masses found in the literature for a further 11 CCSNe and six CCSN remnants, the dust mass at saturation is found to be 0.42$^{+0.09}_{-0.05}$ M⊙. Uncertainty limits for our dust masses were determined from a Bayesian analysis using the affine invariant Markov chain Monte Carlo ensemble sampler emcee with damocles. The best-fitting line profile models for our sample all required grain radii between 0.1 and 0.5 $\mu$m. Our results are consistent with CCSNe forming enough dust in their ejecta to significantly contribute to the dust budget of the Universe.

 

Abstract We present proper motion measurements of the 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 α = 5 h 25 m 01.ˢ71 and δ = −69°38′41.″64 (J2000) with a 1 σ uncertainty of 2.″90. This new CoE measurement is 9.″2 and 10.″8 from two previous CoE estimates based on the geometry of the optically emitting ejecta. We also derive an explosion age of 2770 ± 500 yr, which is consistent with recent age estimates of ≈2500 yr made from 3D ejecta reconstructions. We verified our estimates of the CoE and age using a new automated procedure that detected and tracked the proper motions of 137 knots, with 73 knots that overlap with the visually identified knots. We find that the proper motions of the ejecta are still ballistic, despite the remnant’s age, and are consistent with the notion that the ejecta are expanding into an interstellar medium cavity. Evidence for explosion asymmetry from the parent supernova is also observed. Using the visually measured proper motion measurements and corresponding CoE and age, we compare N132D to other supernova remnants with proper motion ejecta studies. 

Abstract We report multiwavelength observations and characterization of the ultraluminous transient AT 2021lwx (ZTF20abrbeie; aka “Barbie”) identified in the alert stream of the Zwicky Transient Facility (ZTF) using a Recommender Engine For Intelligent Transient Tracking filter on the ANTARES alert broker. From a spectroscopically measured redshift of 0.995, we estimate a peak-observed pseudo-bolometric luminosity of log( L max / [ erg s − 1 ] ) = 45.7 from slowly fading ztf- g and ztf- r light curves spanning over 1000 observer-frame days. The host galaxy is not detected in archival Pan-STARRS observations ( g > 23.3 mag), implying a lower limit to the outburst amplitude of more than 5 mag relative to the quiescent host galaxy. Optical spectra exhibit strong emission lines with narrow cores from the H Balmer series and ultraviolet semi-forbidden lines of Si iii ] λ 1892, C iii ] λ 1909, and  C ii ] λ 2325. Typical nebular lines in Active Galactic Nucleus (AGN) spectra from ions such as [O ii ] and [O iii ] are not detected. These spectral features, along with the smooth light curve that is unlike most AGN flaring activity and the luminosity that exceeds any observed or theorized supernova, lead us to conclude that AT 2021lwx is most likely an extreme tidal disruption event (TDE). Modeling of ZTF photometry with MOSFiT suggests that the TDE was between a ≈14 M ⊙ star and a supermassive black hole of mass M BH ∼ 10 8 M ⊙ . Continued monitoring of the still-evolving light curve along with deep imaging of the field once AT 2021lwx has faded can test this hypothesis and potentially detect the host galaxy. 

Abstract We present a method for analyzing supernova remnants (SNRs) by diagnosing the drivers responsible for structure at different angular scales. First, we perform a suite of hydrodynamic models of the Rayleigh–Taylor instability (RTI) as a supernova (SN) collides with its surrounding medium. Using these models we demonstrate how power spectral analysis can be used to attribute which scales in an SNR are driven by RTI and which must be caused by intrinsic asymmetries in the initial explosion. We predict the power spectrum of turbulence driven by RTI and identify a dominant angular mode that represents the largest scale that efficiently grows via RTI. We find that this dominant mode relates to the density scale height in the ejecta, and therefore reveals the density profile of the SN ejecta. If there is significant structure in an SNR on angular scales larger than this mode, then it is likely caused by anisotropies in the explosion. Structure on angular scales smaller than the dominant mode exhibits a steep scaling with wavenumber, possibly too steep to be consistent with a turbulent cascade, and therefore might be determined by the saturation of RTI at different length scales (although systematic 3D studies are needed to investigate this). We also demonstrate, consistent with previous studies, that this power spectrum is independent of the magnitude and length scales of perturbations in the surrounding medium and therefore this diagnostic is unaffected by “clumpiness” in the circumstellar medium. 

ABSTRACT The large quantities of dust that have been found in a number of high-redshift galaxies have led to suggestions that core-collapse supernovae (CCSNe) are the main sources of their dust and have motivated the measurement of the dust masses formed by local CCSNe. For Cassiopeia A (Cas A), an oxygen-rich remnant of a Type IIb CCSN, a dust mass of 0.6–1.1 M⊙ has already been determined by two different methods, namely (a) from its far-infrared spectral energy distribution and (b) from analysis of the red–blue emission line asymmetries in its integrated optical spectrum. We present a third, independent, method for determining the mass of dust contained within Cas A. This compares the relative fluxes measured in similar apertures from [O iii] far-infrared and visual-region emission lines, taking into account foreground dust extinction, in order to determine internal dust optical depths, from which corresponding dust masses can be obtained. Using this method, we determine a dust mass within Cas A of at least 0.99$^{+0.10}_{-0.09}$ M⊙. 

ABSTRACT We present a hyperspectral cube of the Crab Nebula obtained with the imaging Fourier transform spectrometer SITELLE on the Canada–France–Hawaii telescope. We describe our techniques used to deconvolve the 310 000 individual spectra ($R = 9\, 600$) containing Hα, [N ii] λλ6548, 6583, and [S ii] λλ6716, 6731 emission lines and create a detailed 3D reconstruction of the supernova (SN) remnant (SNR) assuming uniform global expansion. We find that the general boundaries of the 3D volume occupied by the Crab are not strictly ellipsoidal as commonly assumed, and instead appear to follow a ‘heart-shaped’ distribution that is symmetrical about the plane of the pulsar wind torus. Conspicuous restrictions in the bulk distribution of gas consistent with constrained expansion coincide with positions of the dark bays and east–west band of He-rich filaments, which may be associated with interaction with a pre-existing circumstellar disc. The distribution of filaments follows an intricate honeycomb-like arrangement with straight and rounded boundaries at large and small scales that are anticorrelated with distance from the centre of expansion. The distribution is not unlike the large-scale rings observed in SNRs 3C 58 and Cassiopeia A, where it has been attributed to turbulent mixing processes that encouraged outwardly expanding plumes of radioactive 56Ni-rich ejecta. These characteristics reflect critical details of the original SN of 1054 CE and its progenitor star, and may favour a low-energy explosion of an iron-core progenitor. We demonstrate that our main findings are robust despite regions of non-homologous expansion driven by acceleration of material by the pulsar wind nebula.