Properties of gamma-ray decay lines in 3D core-collapse supernova models, with application to SN 1987A and Cas A

Abstract

Comparison of theoretical line profiles to observations provides important tests for supernova explosion models. We study the shapes of radioactive decay lines predicted by current 3D core-collapse explosion simulations, and compare these to observations of SN 1987A and Cas A. Both the widths and shifts of decay lines vary by several thousand kilometers per second depending on viewing angle. The line profiles can be complex with multiple peaks. By combining observational constraints from 56 Co decay lines, 44 Ti decay lines, and Fe IR lines, we delineate a picture of the morphology of the explosive burning ashes in SN 1987A. For M ZAMS = 15 − 20 M ⊙ progenitors exploding with ∼ 1.5 × 10 51 erg, ejecta structures suitable to reproduce the observations involve a bulk asymmetry of the 56 Ni of at least ∼400 km s −1 and a bulk velocity of at least 1500 km s −1 . By adding constraints to reproduce the UVOIR bolometric light curve of SN 1987A up to 600d, an ejecta mass around 14 M ⊙ is favoured. We also investigate whether observed decay lines can constrain the neutron star (NS) kick velocity. The model grid provides a constraint V NS > V redshift , and applying this to SN 1987A gives a NS kick of at least 500 km s −1 . For Cas A, our single model provides a satisfactory fit to the NuSTAR observations and reinforces the result that current neutrino-driven core-collapse SN models achieve enough bulk asymmetry in the explosive burning material. Finally, we investigate the internal gamma-ray field and energy deposition, and compare the 3D models to 1D approximations.

Supernova 1987A: 3D Mixing and light curves for explosion models based on binary-merger progenitors

“…The original model M15-7b-3 shows a good overall agreement with the observed light curve even though the dome of the calculated light curve should be slightly shifted as a whole to earlier times. The latter effect is easily realized by decreasing the mass of the ejected envelope (Utrobin 2005), which is in perfect agreement with the analysis of Xray and gamma-ray observations, and Fe IR line properties of SN 1987A by Jerkstrand et al (2020). Decreasing the ejecta mass and, as a consequence, the mass of slow-moving hydrogen confined to the inner layers (Table 4) shifts both the rising part of the dome-like maximum of the light curve and the branch declining from the maximum to the radioactive tail to earlier times.…”

“…CONSTRAINING THE PROGENITOR MASS Alp et al (2019) showed that our favorite model M15-7b-3 having an ejecta mass of 19.46 M fits the early X-ray and gamma-ray emission of SN 1987A best compared to other binary-merger explosion models. Jerkstrand et al (2020), in turn, found that a good agreement between 3D models and the gamma-ray decay lines and the UVOIR bolometric light curve of SN 1987A could be achieved with a lower ejecta mass of about 14 M . In the light of these results we computed a set of artificial models M15-7b-3-m2, M15-7b-3-m4, and M15-7b-3-m6 with ejecta masses of 17.46 M , 15.46 M , and 13.46 M , respectively (Table 4).…”

“…Alp et al (2019) computed the hard X-ray and gamma-ray emission based on 3D neutrino-driven explosion simulations of Wongwathanarat et al (2013Wongwathanarat et al ( , 2015Wongwathanarat et al ( , 2017 and compared the emergent emission with the corresponding spectra, continuum light curves, and line fluxes of SN 1987A. Jerkstrand et al (2020) repro-duced the gamma-ray decay lines and the UVOIR bolometric light curve of SN 1987A up to 600 days by calculating the total gamma-ray deposition for these 3D simulations and found that an ejecta mass around 14 M is favored for an explosion energy of 1.5 × 10 51 erg.…”

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

“…Grefenstette et al (2017) studied Ti emission in Cas A and found that the bulk Ti emission was tilted 58 • into the plane of the sky away from the observer, implying that the NS is moving 58 • out of the plane of the sky toward the observer. This finding is supported by three-dimensional simulations of a Type IIb progenitor by Wongwathanarat et al (2017) and Jerkstrand et al (2020), which suggested that the NS is moving out of the plane of the sky with an angle of ∼30 • .…”

SN 2017ivv: two years of evolution of a transitional Type II supernova

“…Current 3D SN explosion simulations (e.g. Wongwathanarat, Janka & Müller 2013; Wongwathanarat, Müller & Janka 2015) predict asymmetries in line profiles with line centroid shifts up to about ±500 km s −1 for the IIP case (Jerkstrand et al 2020). For stripped envelope SNe, the scales of these shifts are likely yet larger due to overall higher velocities.…”