Ni Mass Research Articles

The ZTF-BTS Type Ia supernovae luminosity function is consistent with a single progenitor channel for the explosions

ABSTRACT We construct the Type Ia supernovae (SNe Ia) luminosity function (LF) using the Zwicky Transient Facility Bright Transient Survey (BTS) catalogue. While this magnitude-limited survey has an unprecedented number of objects, it suffers from large distance uncertainties and lacks an estimation of host extinction. We bypass these issues by calculating the intrinsic luminosities from the shape parameters of the light curve’s g and r bands, with the luminosities calibrated from the well observed SNe Ia sample of the Carnegie Supernova Project, allowing us to construct, for the first time, the intrinsic LF of SNe Ia. We then use a novel tight relation between the colour stretch and the synthesized 56Ni mass, MNi56, to determine the MNi56 distribution of SNe Ia. We find that the LFs are unimodal, with their peaks in line with previous results, but have a much lower rate of dim events and luminous events. We show that the features on top of the unimodal LF-derived distributions are all compatible with statistical noise, consistent with a single progenitor channel for the explosions. We further derive, for the first time, the SNe Ia distribution of host galaxy extinction, and find a mean selective extinction of E(B − V) ≈ 0.1 and a non-negligible fraction with large, $\gt 1\, \text{mag}$, extinction in the optical bands. The high extinction is typical for luminous SNe, supporting their young population origin.

Core-collapse Supernovae: From Neutrino-driven 1D Explosions to Light Curves and Spectra

Abstract We present bolometric and broadband light curves and spectra for a suite of core-collapse supernova models exploded self-consistently in spherical symmetry within the PUSH framework. We analyze broad trends in these light curves and categorize them based on morphology. We find that these morphological categories relate simply to the progenitor radius and mass of the hydrogen envelope. We present a proof-of-concept sensitive-variable analysis, indicating that an important determining factor in the properties of a light curve within a given category is 56Ni mass. We follow spectra from the photospheric to the nebular phase. These spectra show characteristic iron-line blanketing at short wavelengths and Doppler-shifted Fe ii and Ti ii absorption lines. To enable this analysis, we develop a first-of-its-kind pipeline from a massive progenitor model, through a self-consistent explosion in spherical symmetry, to electromagnetic counterparts. This opens the door to more detailed analyses of the collective properties of these observables. We provide a machine-readable database of our light curves and spectra online at go.ncsu.edu/astrodata.

A low-energy explosion yields the underluminous Type IIP SN 2020cxd

Context. We present our observations and analysis of SN 2020cxd, a low-luminosity (LL), long-lived Type IIP supernova (SN). This object is a clear outlier in the magnitude-limited SN sample recently presented by the Zwicky Transient Facility’s (ZTF) Bright Transient Survey. Aims. We demonstrate that SN 2020cxd is an additional member of the group of LL SNe and we discuss the rarity of LL SNe in the context of the ZTF survey. We consider how further studies of these faintest members of the core-collapse (CC) SN family might help improve the general understanding of the underlying initial mass function for stars that explode. Methods. We used optical light curves (LCs) from the ZTF in the gri bands and several epochs of ultraviolet data from the Neil Gehrels Swift observatory as well as a sequence of optical spectra. We constructed the colour curves and a bolometric LC. Then we compared the evolution of the ejecta velocity and black-body temperature for LL SNe as well as for typical Type II SNe. Furthermore, we adopted a Monte Carlo code that fits semi-analytic models to the LC of SN 2020cxd, which allows for the estimation of the physical parameters. Using our late-time nebular spectra, we also make a comparison against SN II spectral synthesis models from the literature to constrain the progenitor properties of SN 2020cxd. Results. The LCs of SN 2020cxd show a great similarity with those of LL SNe IIP in terms of luminosity, timescale, and colours. Also, the spectral evolution of SN 2020cxd is that of a Type IIP SN. The spectra show prominent and narrow P-Cygni lines, indicating low expansion velocities. This is one of the faintest LL SNe observed, with an absolute plateau magnitude of Mr = −14.5 mag and also one with the longest plateau lengths, with a duration of 118 days. Finally, the velocities measured from the nebular emission lines are among the lowest ever seen in a SN, with an intrinsic full width at half maximum value of 478 km s−1. The underluminous late-time exponential LC tail indicates that the mass of 56Ni ejected during the explosion is much smaller than the average of normal SNe IIP, we estimate M56Ni = 0.003 M⊙. The Monte Carlo fitting of the bolometric LC suggests that the progenitor of SN 2020cxd had a radius of R0 = 1.3 × 1013 cm, kinetic energy of Ekin = 4.3 × 1050 erg, and ejecta mass of Mej = 9.5 M⊙. From the bolometric LC, we estimated the total radiated energy Erad = 1.52 × 1048 erg. Using our late-time nebular spectra, we compared these results against SN II spectral synthesis models to constrain the progenitor zero-age main sequence mass and found that it is likely to be ≲15 M⊙. Conclusions. SN 2020cxd is a LL Type IIP SN. The inferred progenitor parameters and the features observed in the nebular spectrum favour a low-energy, Ni-poor, iron CC SN from a low-mass (∼12 M⊙) red supergiant.

Late-time Hubble Space Telescope Observations of a Hydrogen-poor Superluminous Supernova Reveal the Power-law Decline of a Magnetar Central Engine

Abstract The light-curve diversity of hydrogen-poor superluminous supernovae (SLSNe) has kept open the possibility that multiple power sources account for the population. Specifically, pair-instability explosions (PISNe), which produce large masses of 56Ni, have been argued as the origin of some slowly-evolving SLSNe. Here we present detailed observations of SN 2016inl (=PS16fgt), a slowly-evolving SLSN at z = 0.3057, whose unusually red spectrum matches PS1-14bj, an SLSN with an exceptionally long rise time consistent with a PISN. Ground-based and Hubble Space Telescope data, spanning about 800 rest-frame days, reveal a significant light-curve flattening, similar to that seen in SN 2015bn and much slower than the decline rate expected from radioactive decay of 56Co. We therefore conclude that despite its slow evolution, SN 2016inl is inconsistent with a PISN. Instead, the light-curve evolution matches the expected power-law spindown of a magnetar central engine, but with a shallower power law (L ∝ t −2.8) compared to that in SN 2015bn, indicating a possible difference in the γ-ray opacity between the two events. Analytical modeling indicates typical magnetar engine parameters, but one of the highest ejecta masses (≈20 M ⊙) inferred for an SLSN. Our results indicate that monitoring the late-time light-curve evolution of SLSNe provides a powerful diagnostic of their energy source.

Neutrino-dominated Accretion Flows: A Second Nucleosynthesis Factory in Core-collapse Supernovae and Regulating the Iron Markets in Galaxies

Abstract Cosmic metals are widely believed to be produced by supernovae (SNe) and compact-object mergers. Here, we discuss the nucleosynthesis of neutrino-dominated accretion flows (NDAFs) with outflows in the centers of core-collapse SNe (CCSNe), and show that the outflows from NDAFs can have a significant contribution to the 56Ni abundances of faint explosions if the masses of the progenitor stars are within about 25–50 M ⊙. Less-massive progenitor stars can produce more 56Ni than their more-massive counterparts in the NDAF outflow nucleosynthesis channel. Therefore, we find that the total (i.e., CCSNe and NDAF outflows) 56Ni mass per CCSN depends only weakly upon the mass of the progenitor star. In terms of metallicity evolution, the ratio of 56Fe (produced by the decay of 56Ni) mass to the initial total gas mass can increase by ∼1.95 times if the upper limits of the nucleosynthesis yields from NDAF outflows and CCSNe are considered. Our results might have significant implications for the chemical evolution of the solar neighborhood, galaxies, and active galactic nuclei.

Intermediate-luminosity red transients: Spectrophotometric properties and connection to electron-capture supernova explosions

We present the spectroscopic and photometric study of five intermediate-luminosity red transients (ILRTs), namely AT 2010dn, AT 2012jc, AT 2013la, AT 2013lb, and AT 2018aes. They share common observational properties and belong to a family of objects similar to the prototypical ILRT SN 2008S. These events have a rise time that is less than 15 days and absolute peak magnitudes of between −11.5 and −14.5 mag. Their pseudo-bolometric light curves peak in the range 0.5–9.0 × 1040 erg s−1 and their total radiated energies are on the order of (0.3–3) × 1047 erg. After maximum brightness, the light curves show a monotonic decline or a plateau, resembling those of faint supernovae IIL or IIP, respectively. At late phases, the light curves flatten, roughly following the slope of the 56Co decay. If the late-time power source is indeed radioactive decay, these transients produce 56Ni masses on the order of 10−4 to 10−3 M⊙. The spectral energy distribution of our ILRT sample, extending from the optical to the mid-infrared (MIR) domain, reveals a clear IR excess soon after explosion and non-negligible MIR emission at very late phases. The spectra show prominent H lines in emission with a typical velocity of a few hundred km s−1, along with Ca II features. In particular, the [Ca II] λ7291,7324 doublet is visible at all times, which is a characteristic feature for this family of transients. The identified progenitor of SN 2008S, which is luminous in archival Spitzer MIR images, suggests an intermediate-mass precursor star embedded in a dusty cocoon. We propose the explosion of a super-asymptotic giant branch star forming an electron-capture supernova as a plausible explanation for these events.

ASASSN-15hy: An Underluminous, Red 03fg-like Type Ia Supernova

Abstract We present photometric and spectroscopic observations of the 03fg-like Type Ia supernova (SN Ia) ASASSN-15hy from the ultraviolet (UV) to the near-infrared (NIR). ASASSN-15hy shares many of the hallmark characteristics of 03fg-like SNe Ia, previously referred to as “super-Chandrasekhar” SNe Ia. It is bright in the UV and NIR, lacks a clear i-band secondary maximum, shows a strong and persistent C ii feature, and has a low Si ii λ6355 velocity. However, some of its properties are also extreme among the subgroup. ASASSN-15hy is underluminous (M B,peak = − 19.14 − 0.16 + 0.11 mag), red ( ( B − V ) B max = 0.18 − 0.03 + 0.01 mag), yet slowly declining (Δm 15(B) = 0.72 ± 0.04 mag). It has the most delayed onset of the i-band maximum of any 03fg-like SN. ASASSN-15hy lacks the prominent H-band break emission feature that is typically present during the first month past maximum in normal SNe Ia. Such events may be a potential problem for high-redshift SN Ia cosmology. ASASSN-15hy may be explained in the context of an explosion of a degenerate core inside a nondegenerate envelope. The explosion impacting the nondegenerate envelope with a large mass provides additional luminosity and low ejecta velocities. An initial deflagration burning phase is critical in reproducing the low 56Ni mass and luminosity, while the large core mass is essential in providing the large diffusion timescales required to produce the broad light curves. The model consists of a rapidly rotating 1.47 M ⊙ degenerate core and a 0.8 M ⊙ nondegenerate envelope. This “deflagration core-degenerate” scenario may result from the merger between a white dwarf and the degenerate core of an asymptotic giant branch star.

Influence of Ni doping on the morphological, structural, optical and electrical properties of CuO thin films deposited via a spray pyrolysis

Nanostructured copper oxide (CuO) and Nickel (Ni)-doped CuO thin films with different concentrations of Ni ranging from 2 to 8 at.% were synthesized onto a plain glass substrate at the substrate temperature, 350 °C by a thermal spray pyrolysis technique. Field emission scanning electron microscopy (FESEM) analysis of CuO and Ni-doped CuO thin films detected the closely spaced rock-like nanostructures, evenly distributed on the film surfaces. The average particle sizes of CuO and Ni-doped CuO thin films were calculated from the FESEM and found between 260 and 63 nm. Energy-dispersive X-ray analysis revealed that CuO and Ni-doped CuO thin films were stoichiometric and typically comprised of Cu, O, and Ni. X-ray diffraction analysis showed the monoclinic structure of the films with the most preferred orientation plane ( 1 ‾ 11) along with the (111), ( 2 ‾ 02) and (02 2 ‾ ) crystalline planes. The maximum crystallite size was found at about 81 nm for 6 at% Ni-doped CuO thin film. CuO film showed an optical transmittance of about 33% in the visible-NIR region. Ni-doping enhanced the absorbing nature of CuO thin films in the vis-NIR region of light. With the rise of Ni content in CuO thin films, the optical bandgap gradually increased from 2.28 to 2.78 eV. Resistivity raised from 9.28 × 10 3 to 49.01 × 10 3 Ω-cm with the increase of the amount of Ni. • The FESEM micrographs show that the thin film surface of the CuO and nickel (Ni)-doped CuO thin films comprises irregularly shaped nanoparticles that aggregate to form the columnar surface's morphology. • As the Ni increased in the precursor solution for the preparation of Ni-doped CuO thin films, EDX analysis of the prepared films showed an increase in Ni's mass and atomic percentage. • The films' monoclinic structure with the preferred orientation along with the ( 1 ‾ 11) crystalline plane is shown in the X-ray diffraction analysis. • Ni-doping enhanced the absorbing nature of CuO thin films in the vis-NIR region of light. • The optical band gap and electrical resistivity gradually increased with an increase in the CuO thin film's Ni content.

The Nickel Mass Distribution of Stripped-envelope Supernovae: Implications for Additional Power Sources

Abstract We perform a systematic study of the 56Ni mass (M Ni) of 27 stripped-envelope supernovae (SESNe) by modeling their light-curve tails, highlighting that use of “Arnett’s rule” overestimates M Ni for SESNe by a factor of ∼2. Recently, Khatami & Kasen presented a new model relating the peak time (t p) and luminosity (L p) of a radioactively powered supernova to its M Ni that addresses several limitations of Arnett-like models, but depends on a dimensionless parameter, β. Using observed t p, L p, and tail-measured M Ni values for 27 SESNe, we observationally calibrate β for the first time. Despite scatter, we demonstrate that the model of Khatami & Kasen with empirically calibrated β values provides significantly improved measurements of M Ni when only photospheric data are available. However, these observationally constrained β values are systematically lower than those inferred from numerical simulations, primarily because the observed sample has significantly higher (0.2–0.4 dex) L p for a given M Ni. While effects due to composition, mixing, and asymmetry can increase L p none can explain the systematically low β values. However, the discrepancy can be alleviated if ∼7%–50% of L p for the observed sample comes from sources other than radioactive decay. Either shock cooling or magnetar spin-down could provide the requisite luminosity. Finally, we find that even with our improved measurements, the M Ni values of SESNe are still a factor of ∼3 larger than those of hydrogen-rich Type II SNe, indicating that these supernovae are inherently different in terms of the initial mass distributions of their progenitors or their explosion mechanisms.

SN 2017fgc: A Fast-expanding Type Ia Supernova Exploded in Massive Shell Galaxy NGC 474

Abstract We present extensive optical photometric and spectroscopic observations of the high-velocity (HV) Type Ia supernova (SN Ia) 2017fgc, covering the phase from ∼12 days before to ∼389 days after maximum brightness. SN 2017fgc is similar to normal SNe Ia, with an absolute peak magnitude of M max B ≈ −19.32 ± 0.13 mag and a post-peak decline of Δm 15(B) = 1.05 ± 0.07 mag. Its peak bolometric luminosity is derived as (1.32 ± 0.13) × 1043 erg s−1, corresponding to a 56Ni mass of 0.51 ± 0.03 M ⊙. The light curves of SN 2017fgc are found to exhibit excess emission in the UBV bands in the early nebular phase and pronounced secondary shoulder/maximum features in the RrIi bands. Its spectral evolution is similar to that of HV SNe Ia, with a maximum-light Si ii velocity of 15,000 ± 150 km s−1 and a post-peak velocity gradient of ∼120 ± 10 km s−1 day−1. The Fe ii and Mg ii lines blended near 4300 Å and the Fe ii, Si ii, and Fe iii lines blended near 4800 Å are obviously stronger than those of normal SNe Ia. Inspecting a large sample reveals that the strength of the two blends in the spectra, and the secondary peak in the i/r-band light curves, are found to be positively correlated with the maximum-light Si ii velocity. Such correlations indicate that HV SNe Ia may experience more complete burning in the ejecta and/or that their progenitors have higher metallicity. Examining the birthplace environment of SN 2017fgc suggests that it likely arose from a stellar environment with young and high-metallicity populations.

Novel nickel isolation procedure for a wide range of sample matrices without using dimethylglyoxime for isotope measurements using MC-ICP-MS

Nickel isotope ratios have traditionally been used as an important tracer in cosmochemistry, and recently, it has gained attention in geochemistry, biochemistry, and environmental sciences with the development of MC-ICP-MS. Purification of Ni before isotope measurement is mandatory for obtaining precise data, which has been commonly achieved with ion-exchange chromatography, employing dimethylglyoxime (DMG) as a chelating agent for Ni. However, it has been pointed out that the use of DMG can adversely affect the isotope measurement due to insufficient Ni recovery and mass bias during measurement caused by the remaining DMG. Ni isolation procedures without the usage of DMG were innovated, but they have disadvantages such as the necessity of complex separation methods, high Ni blank, and matrix-dependent Ni recovery. Here, we present a simple Ni isolation procedure without using DMG but with the aid of oxalic acid along with common inorganic acids, achieving near-complete recovery of Ni with low blanks [0.7 ± 0.3 ng (2SD, n = 4)] only using three ion exchange column steps. To validate our method and strengthen the Ni isotope database of reference materials, 60Ni/58Ni of 20 geological reference materials, covering wide matrix compositions, were measured by MC-ICP-MS using the double-spike method. The results have shown that high recovery of Ni, independent of the sample matrix elements was achieved (98 ± 4%) and the 60Ni/58Ni was measured with a 2SD of 0.006–0.084‰ from samples containing 100–200 ng Ni.

Derivation of a Ni bioaccessibility value for screening-level risk assessment of Ni substances in ingested materials including soils.

The objective of the present study was to derive a Ni bioaccessibility value for screening-level risk assessment of Ni substances in ingested materials including soils where multiple Ni substances are expected but not definitively identified. Broad ranges of Ni mass loading and dissolution time of a simple gastric assay were applied to pure Ni substances (removing the confounding factors of soil constituents on dissolution), thus broadening the applicability of the conclusions. The data were also used to support current knowledge of 'read across' for Ni substances. Release of Ni from pure manufactured Ni substances (Ni metal, NiO, NiSO4, Ni3S2, and NiS) was determined relative to Ni mass and substance surface area loading. Mass loadings ranged from 0.33 to 20.0g Ni per L of 0.15M HCl, and dissolution time ranged from 1 to 168h. Proton exhaustion was indicated only at the highest loading (20g/L) of NiO and Ni-M. Dissolution of substances other than NiSO4 was most likely limited by formation of intermediate products at the particle surface or particle agglomeration, impeding access to the principal Ni substance. The bioaccessibility of Ni for these substances was consistent with previously published data: substances other than NiSO4 were < 48% bioaccessible for a variety of gastric assays, which is much lower than all data for NiSO4, the usual reference substance. Thus, we suggest that Ni bioaccessibility data from gastric assays that are most relevant to human exposure can be relied upon to develop scientifically sound screening-level human health RA decisions for Ni contamination in soils and sediments in the absence of detailed Ni speciation.

Effect of Small Amount of Ni Addition on Microstructure and Fatigue Properties of Sn-Sb-Ag Lead-Free Solder.

The effect of the addition volume of Ni on the microstructures and tensile and fatigue properties of Sn-6.4Sb-3.9Ag (mass%) was investigated using micro-size specimens. The addition of Ni into Sn-6.4Sb-3.9Ag tends to increase the number of grains formed in the solidification process and produce a high-angle grain boundary. An amount of 0.1% proof stress of Sn-6.4Sb-3.9Ag decreases with an increase in the Ni addition volume at a strain rate of 2.0 × 10−1 s−1. The effect of the addition of Ni into Sn-6.4Sb-3.9Ag on tensile strength is negligible at both 25 °C and 175 °C. The elongation of Sn-6.4Sb-3.9Ag decreases with an increase in the Ni addition volume at 25 °C according to the fracture mode change from ductile chisel point fracture to shear fracture. The effect of the addition of Ni into Sn-6.4Sb-3.9Ag on the elongation is negligible at 175 °C. The low cycle fatigue test result shows that the fatigue life does not degrade even at 175 °C in all alloys investigated. The fatigue life of Sn-6.4Sb-3.9Ag-0.4Ni (mass%) is superior to those of Sn-6.4Sb-3.9Ag and Sn-6.4Sb-3.9Ag-0.03Ni (mass%) in the high cycle fatigue area. The electron back scattering diffraction (EBSD) analysis result shows that fine recrystallized grains are generated at the cracked area in Sn-6.4Sb-3.9Ag-0.4Ni in the fatigue test at 175 °C, and the crack progresses in a complex manner at the grain boundaries.

Fast Blue Optical Transients Due to Circumstellar Interaction and the Mysterious Supernova SN 2018gep

Abstract The discovery of SN 2018gep (ZTF 18abukavn) challenged our understanding of the late-phase evolution of massive stars and their supernovae (SNe). The fast rise in luminosity of this SN (spectroscopically classified as a broad-lined Type Ic SN) indicates that the ejecta interacts with a dense circumstellar medium (CSM), while an additional energy source such as 56Ni decay is required to explain the late-time light curve. These features hint at the explosion of a massive star with pre-SN mass loss. In this work, we examine the physical origins of rapidly evolving astrophysical transients like SN 2018gep. We investigate the wave-driven mass-loss mechanism and how it depends on model parameters such as progenitor mass and deposition energy, searching for stellar progenitor models that can reproduce the observational data. A model with an ejecta mass ∼2 M ⊙, explosion energy ∼1052 erg, a CSM of mass ∼0.3 M ⊙ and radius ∼1000 R ⊙, and a 56Ni mass ∼0.3 M ⊙ provides a good fit to the bolometric light curve. We also examine how interaction-powered light curves depend more generally on these parameters and how ejecta velocities can help break degeneracies. We find both wave-driven mass loss and mass ejection via pulsational pair instability can plausibly create the dense CSM in SN 2018gep, but we favor the latter possibility.

Self-consistent 3D Supernova Models From −7 Minutes to +7 s: A 1-bethe Explosion of a ∼19 M ⊙ Progenitor

Abstract To date, modern three-dimensional (3D) supernova (SN) simulations have not demonstrated that explosion energies of 1051 erg (=1 bethe=1 B) or more are possible for neutrino-driven SNe of non/slow-rotating M &lt; 20 M ⊙ progenitors. We present the first such model, considering a nonrotating, solar-metallicity 18.88 M ⊙ progenitor, whose final 7 minutes of convective oxygen-shell burning were simulated in 3D and showed a violent oxygen–neon shell merger prior to collapse. A large set of 3D SN models was computed with the Prometheus-Vertex code, whose improved convergence of the two-moment equations with Boltzmann closure allows now to fully exploit the implicit neutrino-transport treatment. Nuclear burning is treated with a 23-species network. We vary the angular grid resolution and consider different nuclear equations of state and muon formation in the proto-neutron star (PNS), which requires six-species transport with coupling of all neutrino flavors across all energy–momentum groups. Elaborate neutrino transport was applied until ∼2 s after bounce. In one case, the simulation was continued to &gt;7 s with an approximate treatment of neutrino effects that allows for seamless continuation without transients. A spherically symmetric neutrino-driven wind does not develop. Instead, accretion downflows to the PNS and outflows of neutrino-heated matter establish a monotonic rise of the explosion energy until ∼7 s post-bounce, when the outgoing shock reaches ∼50,000 km and enters the He layer. The converged value of the explosion energy at infinity (with overburden subtracted) is ∼1 B and the ejected 56Ni mass ≲0.087 M ⊙, both within a few 10% of the SN 1987A values. The final NS mass and kick are ∼1.65 M ⊙ and &gt;450 km s−1, respectively.

SN 2020cpg: an energetic link between Type IIb and Ib supernovae

ABSTRACT Stripped-envelope supernovae (SE-SNe) show a wide variety of photometric and spectroscopic properties. This is due to the different potential formation channels and the stripping mechanism that allows for a large diversity within the progenitors outer envelope compositions. Here, the photometric and spectroscopic observations of SN 2020cpg covering ∼130 d from the explosion date are presented. SN 2020cpg (z = 0.037) is a bright SE-SNe with the B-band peaking at MB = −17.75 ± 0.39 mag and a maximum pseudo-bolometric luminosity of Lmax = 6.03 ± 0.01 × 1042 erg s−1. Spectroscopically, SN 2020cpg displays a weak high- and low-velocity H α feature during the photospheric phase of its evolution, suggesting that it contained a detached hydrogen envelope prior to explosion. From comparisons with spectral models, the mass of hydrogen within the outer envelope was constrained to be ∼0.1 M⊙. From the pseudo-bolometric light curve of SN 2020cpg a 56Ni mass of MNi ∼ 0.27 ± 0.08 M⊙ was determined using an Arnett-like model. The ejecta mass and kinetic energy of SN 2020cpg were determined using an alternative method that compares the light curve of SN 2020cpg and several modelled SE-SNe, resulting in an ejecta mass of Mejc ∼ 5.5 ± 2.0 M⊙ and a kinetic energy of EK ∼ 9.0 ± 3.0 × 1051 erg. The ejected mass indicates a progenitor mass of 18−25 M⊙. The use of the comparative light curve method provides an alternative process to the commonly used Arnett-like model to determine the physical properties of SE-SNe.

Modelling of SN 2013dx associated with the low-redshift GRB130702A points to diversity in GRB/SN properties

ABSTRACT The properties of the broad-lined Type Ic supernova (SN) 2013dx, associated with the long gamma-ray burst GRB 130702A at a redshift z = 0.145, are derived via spectral modelling. SN 2013dx was similar in luminosity to other GRB/SNe, with a derived value of the mass of 56Ni ejected in the explosion of ≈0.4 M⊙. However, its spectral properties suggest a smaller explosion kinetic energy. Radiation transport models were used to derive a plausible mass and density distribution of the SN ejecta in a one-dimensional approximation. While the mass ejected in the explosion that is obtained from the modelling (Mej ≈ 9 M⊙) is similar to that of all other well-studied GRB/SNe, the kinetic energy is significantly smaller (EK ∼ 1052 erg). This leads to a smaller EK/Mej ratio, ≈1051 erg/M⊙, which is reflected in the narrower appearance of the spectral lines. While the low EK does not represent a problem for the scenario in which magnetar energy aids powering the explosion and the nucleosynthesis, it is nevertheless highly unusual. SNe Ic with similar EK have never been seen in coincidence with a GRB, and no well-observed GRB/SN has shown similarly low EK and EK/Mej.

Model Light Curves for Type Ib and Ic Supernovae

Abstract Using the Monte Carlo code SEDONA, multiband photometry and spectra are calculated for supernovae derived from stripped helium stars with presupernova masses of 2.2 to 10.0 M ⊙. The models are representative of evolution in close binaries and have previously been exploded using a parameterized one-dimensional model for neutrino transport. A subset, those with presupernova masses in the range of 2.2–5.6 M ⊙, have many properties in common with observed Type Ib and Ic supernovae, including a median ejected mass near 2 M ⊙, explosion energies near 1 × 1051 erg, typical 56Ni masses of 0.07–0.09 M ⊙, peak times of about 20 days, and a narrow range for the V − R color index 10 days post-V-maximum near 0.3 mag. The median peak bolometric luminosity, near 1042.3 erg s−1, is fainter, however, than several observational tabulations, and the brightest explosion has a bolometric luminosity of only 1042.50 erg s−1. The brightest absolute B, V, and R magnitudes at peak are −17.2, −17.8, and −18.0. These limits are fainter than some allegedly typical Type Ib and Ic supernovae and could reflect problems in our models or in the observational analysis. Helium stars with lower and higher masses also produce interesting transients that may have been observed, including fast, faint, blue transients and long, red, faint Type Ic supernovae. New models are specifically presented for SN 2007Y, SN 2007gr, SN 2009jf, LSQ 13abf, SN 2008D, and SN 2010X.

Supernova 1987A: 3D Mixing and Light Curves for Explosion Models Based on Binary-merger Progenitors

Abstract Six binary-merger progenitors of supernova 1987A (SN 1987A) with properties close to those of the blue supergiant Sanduleak −69°202 are exploded by neutrino heating and evolved until long after shock breakout in 3D and continued for light-curve calculations in spherical symmetry. Our results confirm previous findings for single-star progenitors: (1) 3D neutrino-driven explosions with SN 1987A-like energies synthesize 56Ni masses consistent with the radioactive light-curve tail; (2) hydrodynamic models mix hydrogen inward to minimum velocities below 40 km s−1 compatible with spectral observations of SN 1987A; and (3) for given explosion energy the efficiency of outward radioactive 56Ni mixing depends mainly on high growth factors of Rayleigh–Taylor instabilities at the (C+O)/He and He/H composition interfaces and a weak interaction of fast plumes with the reverse shock occurring below the He/H interface. All binary-merger models possess presupernova radii matching the photometric radius of Sanduleak −69°202 and a structure of the outer layers allowing them to reproduce the observed initial luminosity peak in the first ∼7 days. Models that mix about 0.5 M ⊙ of hydrogen into the He-shell and exhibit strong outward mixing of 56Ni with maximum velocities exceeding the 3000 km s−1 observed for the bulk of ejected 56Ni have light-curve shapes in good agreement with the dome of the SN 1987A light curve. A comparative analysis of the best representatives of our 3D neutrino-driven explosion models of SN 1987A based on single-star and binary-merger progenitors reveals that only one binary model fulfills all observational constraints, except one.

Heavy element contributions of rotating massive stars to interstellar medium

Employing the stellar evolution code Modules for Experiments in Stellar Astrophysics (MESA), we calculate yields of heavy elements from massive stars via stellar wind and core−collapse supernova (CCSN) ejecta to the interstellar medium (ISM). In our models, the initial masses (M ini) of massive stars are taken from 13 to 80 M ⊙, their initial rotational velocities (V) are 0, 300 and 500 km s−1, and their metallicities are [Fe/H] = –3, –2, –1 and 0. The yields of heavy elements coming from stellar winds are mainly affected by stellar rotation which changes the chemical abundances of stellar surfaces via chemically homogeneous evolution, and enhances mass-loss rate. We estimate that the stellar wind can produce heavy element yields of about 10−2 (for low metallicity models) to a mass of several M ⊙ (for low metallicity and rapid rotation models). The yields of heavy elements produced by CCSN ejecta also depend on the large amount of remnant mass which is mainly determined by the mass of the CO-core. Our models calculate that the yields of heavy elements produced by CCSN ejecta can get up to several M ⊙. Compared with stellar wind, CCSN ejecta has a greater contribution to the heavy elements in ISM. We also compare the 56Ni yields calculated in this work with the observational estimate. Our models only explain the 56Ni masses produced by faint SNe or normal SNe with progenitor mass lower than about 25 M ⊙, and greatly underestimate the 56Ni masses produced by stars with masses higher than about 30 M ⊙.