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Lightcurve Modelling of 2,205 ZTF DR2 Type~Ia Supernovae: Implications for SN Ia Physics and Cosmology
High Energy Astrophysical Phenomena · Submitted 2 Feb 2026 · Published version
abstract compiled · 2026-09-23 · no language-model review
The authors' main claim This work provides a step towards physical characterization of the local SN~Ia population while quantifying diversity and environmental dependencies relevant to progenitor physics and precision cosmology.
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The abstract, sentence by sentence
We fit the multi-band light curves of 2,205 Type Ia supernovae (SNe~Ia) from the Zwicky Transient Facility DR2 with a one-zone radioactive decay model with a phenomenological addition to include Fe recombination physics. We find a strong correlation between inferred nickel mass and SALT2 stretch, which our simplified modelling links to longer diffusion times in more massive ejecta, offering a physical basis for the brighter-slower relation. SNe~Ia in low-mass hosts ($\log_{10}(M_*/M_\odot) < 10$) produce $\approx 12\%$ more $^{56}$Ni than those in high-mass hosts, linking the host-galaxy mass step to ejecta properties and hinting at metallicity or age-dependent burning efficiencies. A pseudo-bolometric comparison provides lower limits on the nickel masses, highlighting their sensitivity to SED-level assumptions. Injection-and-recovery tests with realistic ZTF sampling and the same model recover the nickel scale but show significant sensitivity to distance and opacity assumptions; individual-event point estimates are therefore model-dependent. Accounting for selection biases and broad individual-event posteriors, hierarchical modelling of 902 SNe ($z \leq 0.06$) gives Gaussian population distributions with $\mu_{\rm ej} = 1.26 \pm 0.01~M_\odot$ ($\sigma_{\rm ej} = 0.33 \pm 0.01~M_\odot$) and $\mu_{\rm Ni} = 0.64 \pm 0.06~M_\odot$ ($\sigma_{\rm Ni} = 0.42 \pm 0.02~M_\odot$). This work provides a step towards physical characterization of the local SN~Ia population while quantifying diversity and environmental dependencies relevant to progenitor physics and precision cosmology.
background contribution method result interpretation main claim
| # | sentence | role | the authors' own work | states the main conclusion | strength |
|---|---|---|---|---|---|
| s0 | We fit the multi-band light curves of 2,205 Type Ia supernovae (SNe~Ia) from the Zwicky Transient Facility DR2 with a one-zone radioactive decay model with a phenomenological addition to include Fe recombination physics. | method 0.96 | 0.97 | 0.04 | asserted 0.99 |
| s1 | We find a strong correlation between inferred nickel mass and SALT2 stretch, which our simplified modelling links to longer diffusion times in more massive ejecta, offering a physical basis for the brighter-slower relation. | result 0.57 | 0.97 | 0.24 | asserted 0.99 |
| s2 | SNe~Ia in low-mass hosts ($\log_{10}(M_*/M_\odot) < 10$) produce $\approx 12\%$ more $^{56}$Ni than those in high-mass hosts, linking the host-galaxy mass step to ejecta properties and hinting at metallicity or age-dependent burning efficiencies. | result 0.90 | 0.93 | 0.14 | asserted 0.82 |
| s3 | A pseudo-bolometric comparison provides lower limits on the nickel masses, highlighting their sensitivity to SED-level assumptions. | result 0.40 | 0.91 | 0.03 | asserted 0.99 |
| s4 | Injection-and-recovery tests with realistic ZTF sampling and the same model recover the nickel scale but show significant sensitivity to distance and opacity assumptions; individual-event point estimates are therefore model-dependent. | limitation 0.99 | 0.97 | 0.05 | asserted 1.00 |
| s5 | Accounting for selection biases and broad individual-event posteriors, hierarchical modelling of 902 SNe ($z \leq 0.06$) gives Gaussian population distributions with $\mu_{\rm ej} = 1.26 \pm 0.01~M_\odot$ ($\sigma_{\rm ej} = 0.33 \pm 0.01~M_\odot$) and $\mu_{\rm Ni} = 0.64 \pm 0.06~M_\odot$ ($\sigma_{\rm Ni} = 0.42 \pm 0.02~M_\odot$). | result 1.00 | 0.97 | 0.38 | asserted 1.00 |
| s6 | This work provides a step towards physical characterization of the local SN~Ia population while quantifying diversity and environmental dependencies relevant to progenitor physics and precision cosmology. | interpretation 0.70 | 0.77 | 0.33 | asserted 0.59 |
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The paper
Original abstract
We fit the multi-band light curves of 2,205 Type Ia supernovae (SNe~Ia) from the Zwicky Transient Facility DR2 with a one-zone radioactive decay model with a phenomenological addition to include Fe recombination physics. We find a strong correlation between inferred nickel mass and SALT2 stretch, which our simplified modelling links to longer diffusion times in more massive ejecta, offering a physical basis for the brighter-slower relation. SNe~Ia in low-mass hosts ($\log_{10}(M_*/M_\odot) < 10$) produce $\approx 12\%$ more $^{56}$Ni than those in high-mass hosts, linking the host-galaxy mass step to ejecta properties and hinting at metallicity or age-dependent burning efficiencies. A pseudo-bolometric comparison provides lower limits on the nickel masses, highlighting their sensitivity to SED-level assumptions. Injection-and-recovery tests with realistic ZTF sampling and the same model recover the nickel scale but show significant sensitivity to distance and opacity assumptions; individual-event point estimates are therefore model-dependent. Accounting for selection biases and broad individual-event posteriors, hierarchical modelling of 902 SNe ($z \leq 0.06$) gives Gaussian population distributions with $\mu_{\rm ej} = 1.26 \pm 0.01~M_\odot$ ($\sigma_{\rm ej} = 0.33 \pm 0.01~M_\odot$) and $\mu_{\rm Ni} = 0.64 \pm 0.06~M_\odot$ ($\sigma_{\rm Ni} = 0.42 \pm 0.02~M_\odot$). This work provides a step towards physical characterization of the local SN~Ia population while quantifying diversity and environmental dependencies relevant to progenitor physics and precision cosmology.
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References
How the literature uses it
2 arXiv papers cite this in 2 sentences
Papers citing it · 1 sentence without a confident label
Cites it as background 1 paper
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These models have been applied to large samples of core-collapse [ref] , and thermonuclear SNe [ref] , and inferences drawn from such fits are then used to compare explosion mechanisms, nucleosynthetic yields, and the relation between different classes of supernovae.
Signatures of $^{56}$Ni Mixing and Neutron-rich Ejecta in Supernovae · Introduction · 0.83
What it cites · 56 sentences without a confident label
Uses the method or tool of 7 papers
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The hyper-parameter posterior is given by [ref] , [equation] Here $d_i$ represents the data (light curves) for the $N_obs = 902$ observed events, $π(Λ)$ is the prior on our population parameters, and $ℒ$ is the likelihood for the population hyperparameters.
An introduction to Bayesian inference in gravitational-wave astronomy: parameter estimation, model selection, and hierarchical models · Hierarchical inference on low-redshift sample · 0.95
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The hyper-parameter posterior is given by [ref] , [equation] Here $d_i$ represents the data (light curves) for the $N_obs = 902$ observed events, $π(Λ)$ is the prior on our population parameters, and $ℒ$ is the likelihood for the population hyperparameters.
Extracting distribution parameters from multiple uncertain observations with selection biases · Hierarchical inference on low-redshift sample · 0.95
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To sample the posterior we use the model and likelihoods implemented in Redback [ref] with the the nested sampler PyMultiNest [ref] via the Bilby [ref] interface.
MultiNest: an efficient and robust Bayesian inference tool for cosmology and particle physics · Inference · 1.00
Uses data or values from 2 papers
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Our analysis draws on the Zwicky Transient Facility (ZTF) Data Release 2 (DR2) sample of spectroscopically confirmed Type Ia supernovae [ref] .
ZTF SN Ia DR2: Overview · Sample Selection and Properties · 1.00
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Host-galaxy stellar masses are available for 2,151 SNe ($97.6%$) of the sample considered in this work [ref] and span $6.0 < log_10(M_*/M_⊙) < 11.5$ with a median of 9.8; the sample is evenly divided across the canonical $log_10(M_*/M_⊙) = 10$ mass step threshold [ref] , providing leverage on environmental trends.
The Dependence of Type Ia Supernova Luminosities on their Host Galaxies · Sample Selection and Properties · 1.00
Compares with 5 papers
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The nickel mass distribution for the selected population has a mean $M_Ni= 1.21 M_⊙$ with a standard deviation of $0.3$ M$_⊙$, higher than the canonical $∼$0.6 M$_⊙$ [ref] .
Consistent estimates of (56)Ni yields for type Ia supernovae · Physical Parameter Distributions · 0.97
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This is again more consistent with estimates from smaller, albeit (also biased) samples [ref] , especially given the large uncertainty.
Measuring nickel masses in Type Ia supernovae using cobalt emission in nebular phase spectra · Redshift-limited sub-sample · 0.97
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Given that the nickel mass strongly correlates with $x_1$, this plot is directly comparable to the known and expected trends between $x_1$ and host galaxy properties [ref] .
The Dependence of Type Ia Supernova Luminosities on their Host Galaxies · Host Galaxy Correlations · 0.87
Cites as support 1 paper
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We stress that these modifications are all phenomenological, and motivated by the real physics seen in radiative-transfer simulations [ref] , which is otherwise too computationally expensive to implement in inference-capable models.
Secondary Maximum in the Near-Infrared Lightcurves of Type Ia Supernovae · Model · 0.96
Cites as background 14 papers
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In sub-$M_Ch$ models, double-detonation is triggered on a less massive WD [ref] .
Detonations in Sub-Chandrasekhar Mass C+O White Dwarfs · Introduction · 0.95
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In Chandrasekhar-mass ($M_Ch ≈1.4$ M$_⊙$) models, the explosion proceeds via delayed detonation or deflagration-to-detonation transition [ref] .
Explosion Models for Type Ia Supernovae: A Comparison with Observed Light Curves, distances, H_o and q_o · Introduction · 0.96
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The most popular model involves the thermonuclear runaway of a carbon-oxygen white dwarf (WD) in a binary system, but the specific progenitor channel—single-degenerate (SD) accretion or double-degenerate (DD) merger—is highly debated [ref] .
Observational clues to the progenitors of Type-Ia supernovae · Introduction · 0.96
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