Type Ia Research Articles

Lensed Type Ia Supernova “Encore” at z = 2: The First Instance of Two Multiply Imaged Supernovae in the Same Host Galaxy

A bright (m F150W,AB = 24 mag), z = 1.95 supernova (SN) candidate was discovered in JWST/NIRCam imaging acquired on 2023 November 17. The SN is quintuply imaged as a result of strong gravitational lensing by a foreground galaxy cluster, detected in three locations, and remarkably is the second lensed SN found in the same host galaxy. The previous lensed SN was called “Requiem,” and therefore the new SN is named “Encore.” This makes the MACS J0138.0−2155 cluster the first known system to produce more than one multiply imaged SN. Moreover, both SN Requiem and SN Encore are Type Ia SNe (SNe Ia), making this the most distant case of a galaxy hosting two SNe Ia. Using parametric host fitting, we determine the probability of detecting two SNe Ia in this host galaxy over a ∼10 yr window to be ≈3%. These observations have the potential to yield a Hubble constant (H 0) measurement with ∼10% precision, only the third lensed SN capable of such a result, using the three visible images of the SN. Both SN Requiem and SN Encore have a fourth image that is expected to appear within a few years of ∼2030, providing an unprecedented baseline for time-delay cosmography.

Skeletal Kinetics Reduction for Astrophysical Reaction Networks

A novel methodology is developed to extract accurate skeletal reaction models for nuclear combustion. Local sensitivities of isotope mass fractions with respect to reaction rates are modeled based on the forced optimally time-dependent (f-OTD) scheme. These sensitivities are then analyzed temporally to generate skeletal models. The methodology is demonstrated by conducting skeletal reduction of constant density and temperature burning of carbon and oxygen relevant to Type Ia supernovae (SNe Ia). The 495-isotopes Torch model is chosen as the detailed reaction network. A map of maximum production of 56Ni in SNe Ia is produced for different temperatures, densities, and proton-to-neutron ratios. The f-OTD simulations and the sensitivity analyses are then performed with initial conditions from this map. A series of skeletal models are derived and their performances are assessed by comparison against currently existing skeletal models. Previous models have been constructed intuitively by assuming the dominance of α-chain reactions. The comparison of the newly generated skeletal models against previous models is based on the predicted energy release and 44Ti and 56Ni abundances by each model. The consequences of y e ≠ 0.5 in the initial composition are also explored where y e is the electron fraction. The simulated results show that 56Ni production decreases by decreasing y e as expected, and that the 43Sc is a key isotope in proton and neutron channels toward 56Ni production. It is shown that an f-OTD skeletal model with 150 isotopes can accurately predict the 56Ni abundance in SNe Ia for y e ≲ 0.5 initial conditions.

Phantom Scalar Field Cosmologies Constrained by Early Cosmic Measurements

In this work, we explore new constraints on phantom scalar field cosmologies with a scalar field employing early-time catalogs related to CMB measurements, along with the local standard observables, like Supernovae Type Ia (SNIa), H(z) measurements (Cosmick clocks), and Baryon Acoustic Oscillation (BAO) baselines. In particular, we studied a tracker phantom field with hyperbolic polar coordinates that have been proposed in the literature. The main goal is to obtain precise cosmological constraints for H0 and σ8, in comparison to other constructions that present tension in early cosmological parameters. Our results show that phantom scalar field cosmologies have a reduced statistical tension on H0 that it is less than 3σ using model-independent CMB catalogs as SPT-3G+WMAP9 and ACTPol DR-4+WMAP9 baselines. This suggests that these models, using a different phantom potential, might address the Hubble constant problem and reduce the systematics involved.

Chemical evolution of the Galactic bulge with different stellar populations

The metallicity distribution function (MDF) of the Galactic bulge is characterized by a multi-peak shape, with a metal-poor peak centered at $ Fe/H sim-0.3 $ dex and a metal-rich peak centered at $ Fe/H sim+0.3 $ dex. The bimodality of the MDF is also reflected in the alpha /Fe versus Fe/H abundance ratios, suggesting the presence of different stellar populations in the bulge. In this work we aim to reproduce the observed MDF of the Galactic bulge by testing a scenario in which the metal-poor component of the bulge is formed by stars formed in situ, during a strong burst of star formation, while the metal-rich population is formed by stars created in situ during a second burst of star formation and/or stars accreted from the innermost part of the Galactic disk as an effect of a growing bar. We adopted a chemical evolution model that is able to follow the evolution of several chemical species with detailed nucleosynthesis prescriptions. In particular, because of the importance of the production of Fe in constraining the MDF, close attention is paid to the production of this element in both Type Ia supernovae and massive stars. In particular, we included yields from rotating massive stars with different rotational velocity prescriptions. Our model also takes the infall and outflow of gas into account, as well as the effect of stellar migration. Results are compared to sim 13000 stars from the SDSS/APOGEE survey that belong to the region located at a Galactocentric distance $ R_ GC kpc We successfully reproduce the observed double-peak shape of the bulge MDF as well as the abundance trends of the alpha elements relative to Fe by assuming both (i) a multi-burst star formation history with a quenching of the first burst of $ 10^2\ Myr $ and (ii) migration of stars from the innermost part of the Milky Way disk, as an effect of a growing bar. According to our results, the fraction of the stellar mass of the bulge-bar that belongs to the inner disk is $ sim40<!PCT!> $. In terms of the nucleosynthesis, we conclude that models that assume either no rotation for massive stars or a distribution of rotational velocities that favors slow rotation at high metallicities best reproduce the observed MDF as well as the alpha /Fe and the Ce/Fe versus Fe/H abundance patterns.

Some classes of interacting two-fluid model of the expanding universe

Abstract We consider interacting dark matter-dark energy models arising out of a general interaction term $Q=f(\rho_{m},\rho_{d},\dot{\rho}_{m},\dot{\rho}_{d}).$ Here $f$ is a functional relation connecting the energy densities $\rho_{m}$ and $\rho_{d}$ and their derivatives w.r.t. time $t.$ In our model we consider two interacting barotropic fluid with constant equation of state $\omega_{m}$ and $\omega_{d}.$ By considering a dynamical interaction between them we trace out the cosmological evolution dynamics of the universe. We analytically solve the model by considering a constant ratio between the two fluids and then track the corresponding analytical results using observational data from the baryon acoustic oscillation measurements, Type Ia supernovae measurements and the local Hubble constant measurements. From this general setting we introduce three different models and nine different interaction function. Our final aim is to set up a comparative analysis of the various class of models under the different interaction function using common theoretical and numerical analysis.

The die for the production of the hammered kaptorgas from Kouřim, Central Bohemia

Kaptorgas were small trapezoidal boxes with lids worn by women and girls in early medieval central Europe as magic or protective amulets. The paper presents a new find of a bronze cast die for hammering the front side of kaptorgas, which was excavated at the Nad Dolnicí settlement site located in the hinterland of the important central Bohemian hillfort of Kouřim. The die was used to produce type 1A kaptorgas with a motif of a four-legged eared gryphon with an indication of a wing and a tail ending in a floral decorative element. Although kaptorgas with this particular motif have not been recorded in Bohemia, it has analogies in Bulgaria and Poland. Based on the stylistic assessment of this originally Mediterranean motif and the chronology of type IA kaptorgas in Bohemia, the die can be dated to the 10th and beginning of the 11th century. X-Ray fluorescence analysis and elemental mapping of the object's surface show that it was made from bronze with a significant lead admixture and a small admixture of zinc. The die is discussed in terms of the spread of Mediterranean motifs and their adaptation by local craftsmen.

Dark energy nature of logarithmic f(R,Lm)-gravity models with observational constraints

This work explores the dark energy nature of logarithmic [Formula: see text]-gravity models with observational constraints, where [Formula: see text] represents the matter Lagrangian for perfect fluid and R is the Ricci-scalar curvature. With a matter Lagrangian [Formula: see text], a flat FLRW space–time metric and an arbitrary function [Formula: see text], where [Formula: see text] is a positive model parameter, we have derived the field equations of this model. By using the Hubble function, we have been able to solve the energy conservation equation and create a relationship between [Formula: see text], [Formula: see text] and [Formula: see text]. Using the most recent two observational datasets as 32 [Formula: see text] and 1048 Pantheon SNe Ia datasets, we conducted MCMC analysis. We have obtained best fit values of model parameters with [Formula: see text] errors and using these values, we have explored the cosmological properties of the model. We have performed om diagnostic analysis for the model and estimated the present age of the universe. Thus our derived model presents a transit phase decelerating to accelerating model without dark energy term [Formula: see text]. We found that the effective equation of state parameter is in the range [Formula: see text] over [Formula: see text] with present value [Formula: see text].

Age Analysis of Extrasolar Planets: Insight from Stellar Isochrone Models

There is growing evidence from stellar kinematics and galactic chemical evolution suggesting that giant planets (M P ≥ 0.3M J ) are relatively young compared to the most commonly occurring population of small planets (M P < 0.3M J ). To further test the validity of these results, we analyzed the ages for a large number of 2336 exoplanet hosting stars determined using three different but well-established isochrone fitting models, namely, PARSEC, MIST, and Yonsei Yale. As input parameters, we used Gaia DR3 parallaxes, magnitudes, and photometric temperature, as well as spectroscopically determined more accurate temperatures and metallicities from the Sweet Catalog. Our analysis suggests that ∼50%–70% of stars with planets are younger than the Sun. We also find that, among the confirmed exoplanetary systems, stars hosting giant planets are even younger compared to small planet hosts. The median age of ∼2.61–3.48 Gyr estimated for the giant planet-hosting stars (depending on the model input parameters) suggests that the later chemical enrichment of the galaxy by the iron-peak elements, largely produced from Type Ia supernovae, may have paved the way for the formation of gas giants. Furthermore, within the giant planet population itself, stars hosting hot Jupiters (orbital period ≤10 days) are found to be younger compared to the stellar hosts of cool and warm Jupiters (orbital period >10 days), implying that hot Jupiters could be the youngest systems to emerge in the progression of planet formation.

A closer look at the host-galaxy environment of high-velocity Type Ia supernovae

Abstract Recent studies suggested that the ejecta velocity of Type Ia supernova (SN Ia) is a promising indicator in distinguishing the progenitor systems and explosion mechanisms. By classifying the SNe Ia based on their ejecta velocities, studies found SNe Ia with high $\mathrm{Si}\, \small {II}\, \lambda 6355$ velocities (HV SNe Ia; $v \gtrsim 12000$ km s−1) tend to be physically different from their normal-velocity counterparts (NV SNe Ia). In this work, we revisit the low-z sample studied in previous work and closely look into the spatially resolved environment local to the site of SN explosion. Our results reveal a possible trend (at 2.4σ significance) that HV SNe Ia are likely associated with older stellar populations than NV SNe Ia. While the trend is inconclusive, the local host-galaxy sample studied in this work is likely skewed toward massive galaxies, limiting the parameter space that we would like to investigate from the original parent sample. Nevertheless, our results do not rule out the possibility that parameters other than the host-galaxy age (such as metallicity) could be the underlying factors driving the differences between HV and NV SNe Ia due to the limitation of our dataset.

Measuring the reionization optical depth without large-scale CMB polarization

We study the possibility of measuring the optical depth at reionization τ without relying on large-scale cosmic microwave background (CMB) polarization. Our analysis is driven by the need to obtain competitive measurements that can validate the state-of-the-art constraints on this parameter, widely based on E-mode polarization measurements at ℓ≤30. This need is partially motivated by the typical concerns regarding anomalies observed in the Planck large-scale CMB data as well as by the remarkable fact that, excluding these latter, τ consistently exhibits correlations with anomalous parameters, such as Alens and Ωk, suggesting that slightly higher values of the optical depth at reionization could significantly alleviate or even eliminate anomalies. Within the Λ cold dark matter model, our most constraining result is τ=0.080±0.012, obtained by combining Planck temperature and polarization data at ℓ&gt;30, the Atacama Cosmology Telescope (ACT) and Planck measurements of the lensing potential, baryon acoustic oscillations (BAOs), and type-Ia supernova data from the Pantheon+catalog. Notably, using only ACT temperature, polarization, and lensing data in combination with BAOs and supernovae, we obtain τ=0.076±0.015, which is entirely independent of Planck. The relative precision of these results is approaching the constraints based on large-scale CMB polarization (τ=0.054±0.008). Despite the overall agreement, we report a slight 1.8σ shift toward larger values of τ. We also test how these results change by extending the cosmological model. While in many extensions they remain robust, in general, obtaining precise measurements of τ may become significantly more challenging. Published by the American Physical Society 2024

Purification of Recombinant E. Coli Topoisomerase III for Structure-Based Drug Design Using Protein Crystallization

Type IA Topoisomerases are ubiquitous enzymes found throughout all life forms and species. These topoisomerases relieve the topographical constrains formed by DNA during processes like replication and transcription via a cleavage-religation mechanism performed through a catalytically active tyrosine residue in the primary structure of the enzyme. E. coli Topoisomerase III (EtopIII) is a type of Type IA topoisomerase, and its main function in the cell is as a decatenase, which means that it unlinks circular or intertwined pieces of genetic material and creates two unlinked segments of DNA from a singular linked chain. Structure-based determination of the enzyme’s three-dimensional structure via crystallization could be beneficial in finding a novel antibiotic drug that is able to inhibit this enzyme in vivo, a solution that is sorely needed in a world where antibiotic-resistant bacteria are an ever-growing problem. The crystallization of the enzyme can be undertaken by truncating a part of the C-terminal of the enzyme that makes it harder for it to crystallize and introduce a DNA/RNA ligand to observe its binding interactions with said substrate. For this to happen, the truncated recombinant mutant must be purified and concentrated to desirable levels for crystallization. The results of the experiment show that out of 4L of bacterial starting culture, a total of 34.57 mg of protein was able to be purified. This protein was then sent for crystallization experiments, of which results are still pending, but preliminary results indicate that the protein quickly aggregates in one of the RNA ligand conditions, which elicits a change in protocol for future purifications. Furthermore, results from a relaxation assay indicate that the protein exhibits some relaxation activity even after the truncation of the C-terminal chain. These results could expand the knowledge of this enzyme for future structure-based drug development.

Quantitative modelling of type Ia supernovae spectral time series: Constraining the explosion physics

Abstract Multiple explosion mechanisms have been proposed to explain type Ia supernovae (SNe Ia). Empirical modelling tools have also been developed that allow for fast, customised modelling of individual SNe and direct comparisons between observations and explosion model predictions. Such tools have provided useful insights, but the subjective nature with which empirical modelling is performed makes it difficult to obtain robust constraints on the explosion physics or expand studies to large populations of objects. Machine learning accelerated tools have therefore begun to gain traction. In this paper, we present riddler, a framework for automated fitting of SNe Ia spectral sequences up to shortly after maximum light. We train a series of neural networks on realistic ejecta profiles predicted by the W7 and N100 explosion models to emulate full radiative transfer simulations and apply nested sampling to determine the best-fitting model parameters for multiple spectra of a given SN simultaneously. We show that riddler is able to accurately recover the parameters of input spectra and use it to fit observations of two well-studied SNe Ia. We also investigate the impact of different weighting schemes when performing quantitative spectral fitting and show that best-fitting models and parameters are highly dependent on the assumed weighting schemes and priors. As spectroscopic samples of SNe Ia continue to grow, automated spectral fitting tools such as riddler will become increasingly important to maximise the physical constraints that can be gained in a quantitative and consistent manner.

Endovascular Salvage of Type Ia and Ib Endoleaks Using a Physician-Modified Fenestrated/Branched Endograft and an Iliac Branch Device Via Unilateral Transfemoral Arterial Access.

This study aims to explore the feasibility and effectiveness of a unilateral transfemoral access endovascular salvage technique for complex abdominal aortic aneurysms with concurrent type Ia and Ib endoleaks following previous endovascular repair. A 69-year-old female with multiple comorbidities presented with an extent IV thoracoabdominal aortic aneurysm complicated by type Ia and Ib endoleaks and chronically occluded left iliac endoprosthesis after prior endovascular repair. Given the patient's medical complexities, open explant repair was deemed high risk. The case was successfully managed using a physician-modified fenestrated/branched endograft (PM-F/BEVAR) and an iliac branch device (IBD) deployed through a single percutaneous transfemoral access. The presented case demonstrates the safety and efficacy of PM-F/BEVAR with concomitant IBD deployment via unilateral transfemoral access. This innovative approach allows endovascular salvage in cases with restricted iliofemoral access and avoids the complexities associated with upper extremity or aortic arch manipulation. While acknowledging the technical challenges, this technique offers a viable alternative for salvaging failed endovascular repairs, emphasizing the importance of real-time modifications in achieving successful outcomes. Further studies and long-term follow-up are warranted to validate the broader applicability and durability of this approach in the management of complex abdominal aortic aneurysms with multiple endoleaks. Although not the conventional approach, unilateral transfemoral access can be utilized to implant either a physician-modified fenestrated aortic endograft or an iliac branch device. Such an approach avoids complicating issues related to upper extremity access. This innovative technique may be necessary when there is a failed prior EVAR in the setting of significant contralateral iliofemoral occlusive disease. Doing both procedures in the same setting to resolve a type Ia and Ib endoleak is feasible as demonstrated in this case report. Expanding the endovascular armamentarium to address EVAR failure will be increasingly useful in the future, especially given the morbidity profile of EVAR explantation.

Governing accelerating Universe via newly reconstructed Hubble parameter by employing empirical data simulations

A new parametrization of the Hubble parameter is proposed to explore the issue of the cosmological landscape. The constraints on model parameters are derived through the Markov Chain Monte Carlo (MCMC) method by employing a comprehensive union of datasets such as 34 data points from cosmic chronometers (CC), 42 points from baryonic acoustic oscillations (BAO), a recently updated set of 1701 Pantheon+ (P22) data points derived from Type Ia supernovae (SNeIa), and 162 data points from gamma-ray bursts (GRBs). Furthermore, the models are compared by using the Akaike Information Criterion (AIC) and Bayesian Information Criterion (BIC), so that a comparative assessment of model performance can be available. Additionally, we compare the Dainotti relation via Gaussian likelihood analysis versus new likelihoods and Calibration of the Dainotti relation through a model-independent method. The kinematic behavior of the models is also investigated by encompassing the transition from deceleration to acceleration and the evolution of the jerk parameter. From the analysis of the parametric models, it is strongly indicated that the Universe is currently undergoing an accelerated phase with diagnostics of the model validating the quintessence phase.

Two Shell-burning White Dwarfs in Symbiotics of the Small Magellanic Cloud

SMC3 and Lin358 are super-soft X-ray sources (SSS) in symbiotics of the Small Magellanic Cloud. They have been observed as SSS for over 30 yr. We present new observations done in 2014, 2021 and in 2023 with XMM-Newton, NICER, and Chandra. Lin358 is modeled with an effective temperature around 200,000 K, and a maximum flux value around 8.25 × 10−13 erg cm−2 s−1 in 2021. An observation close to periastron revealed hardening of the source. SMC3 is known to undergo an X-ray obscuration approximately every 4.5 yr; we measured the peak X-ray flux of 4.12 × 10−13 in 2014 with the Chandra Low Energy Transmission Grating. Models indicate an effective temperature of about 500,000 K, consistent with previous findings, and increasing luminosity excursion between maxima and minima. We suggest that with such high effective temperature, indicative of steady shell burning, the possibility these systems are on the path to type Ia supernova is worth considering.

Cosmological Inference from within the Peculiar Local Universe

The existence of ‘peculiar’ velocities due to the formation of cosmic structure marks a point of discord between the real universe and the usually assumed Friedmann–Lemaítre–Robertson–Walker metric, which accomodates only the smooth Hubble expansion on large scales. In the standard ΛCDM model framework, Type Ia supernovae data are routinely “corrected” for the peculiar velocities of both the observer and the supernova host galaxies relative to the cosmic rest frame, in order to infer evidence for acceleration of the expansion rate from their Hubble diagram. However, observations indicate a strong, coherent local bulk flow that continues outward without decaying out to a redshift z≳0.1, contrary to the ΛCDM expectation. By querying the halo catalogue of the Dark Sky Hubble-volume N-body simulation, we find that an observer placed in an unusual environment like our local universe should see correlations between supernovae in the JLA catalogue that are 2–8 times stronger than seen by a typical or Copernican observer. This accounts for our finding that peculiar velocity corrections have a large impact on the value of the cosmological constant inferred from supernova data. We also demonstrate that local universe-like observers will infer a downward biased value of the clustering parameter S8 from comparing the density and velocity fields. More realistic modelling of the peculiar local universe is thus essential for correctly interpreting cosmological data.

A case study of a liver transplant-treated patient with glycogen storage disease type Ia presenting with multiple inflammatory hepatic adenomas: an analysis of clinicopathologic and genetic data

BackgroundGlycogen storage disease (GSD) is a disease caused by excessive deposition of glycogen in tissues due to genetic disorders in glycogen metabolism. Glycogen storage disease type I (GSD-I) is also known as VonGeirk disease and glucose-6-phosphatase deficiency. This disease is inherited in an autosomal recessive manner, and both sexes can be affected. The main symptoms include hypoglycaemia, hepatomegaly, acidosis, hyperlipidaemia, hyperuricaemia, hyperlactataemia, coagulopathy and developmental delay.Case presentationHere, we present the case of a 13-year-old female patient with GSD Ia complicated with multiple inflammatory hepatic adenomas. She presented to the hospital with hepatomegaly, hypoglycaemia, and epistaxis. By clinical manifestations and imaging and laboratory examinations, we suspected that the patient suffered from GSD I. Finally, the diagnosis was confirmed by liver pathology and whole-exome sequencing (WES).WES revealed a synonymous mutation, c.648 G > T (p.L216 = , NM_000151.4), in exon 5 and a frameshift mutation, c.262delG (p.Val88Phefs*14, NM_000151.4), in exon 2 of the G6PC gene. According to the pedigree analysis results of first-generation sequencing, heterozygous mutations of c.648 G > T and c.262delG were obtained from the patient's father and mother.Liver pathology revealed that the solid nodules were hepatocellular hyperplastic lesions, and immunohistochemical (IHC) results revealed positive expression of CD34 (incomplete vascularization), liver fatty acid binding protein (L-FABP) and C-reactive protein (CRP) in nodule hepatocytes and negative expression of β-catenin and glutamine synthetase (GS). These findings suggest multiple inflammatory hepatocellular adenomas. PAS-stained peripheral hepatocytes that were mostly digested by PAS-D were strongly positive.This patient was finally diagnosed with GSD-Ia complicated with multiple inflammatory hepatic adenomas, briefly treated with nutritional therapy after diagnosis and then underwent living-donor liver allotransplantation.After 14 months of follow-up, the patient recovered well, liver function and blood glucose levels remained normal, and no complications occurred.ConclusionThe patient was diagnosed with GSD-Ia combined with multiple inflammatory hepatic adenomas and received liver transplant treatment. For childhood patients who present with hepatomegaly, growth retardation, and laboratory test abnormalities, including hypoglycaemia, hyperuricaemia, and hyperlipidaemia, a diagnosis of GSD should be considered. Gene sequencing and liver pathology play important roles in the diagnosis and typing of GSD.

Current dialyzer classification in Japan and mortality risk in patients undergoing hemodialysis

Dialyzers are classified into five types based on their β2-microglobulin clearance rate and albumin sieving coefficient: Ia, Ib, IIa, and IIb. In addition, a new classification system introduced a type S dialyzer. However, limited information is available regarding the impact of dialyzer type on patient outcomes. A cohort study was conducted using data from the Japanese Society for Dialysis Therapy Renal Data Registry database. Total 181,804 patients on hemodialysis (HD) were included in the study, categorized into four groups (type Ia, IIa, IIb, and S). The associations between each group and two-year all-cause mortality were assessed using Cox proportional hazard models. Furthermore, propensity score-matching analysis was performed. By the end of 2019, 34,185 patients on dialysis had died. After adjusting for all confounders, the risk for all-cause mortality was significantly lower in the type IIa, and S groups than in the type Ia group. These significant findings were consistent after propensity score matching. In conclusion, our findings suggest that super high-flux dialyzers, with a β2-microglobulin clearance of ≥ 70 mL/min, may be beneficial for patients on HD, regardless of their albumin sieving coefficient. In addition, type S dialyzers may be beneficial for elderly and malnourished patients on dialysis.Trial registration number: UMIN000018641

Scalable hierarchical BayeSN inference: investigating dependence of SN Ia host galaxy dust properties on stellar mass and redshift

ABSTRACT We apply the hierarchical probabilistic spectral energy distribution (SED) model bayesn to analyse a sample of 475 type Ia supernovae (0.015 &amp;lt; z &amp;lt; 0.4) from Foundation, DES3YR and PS1MD to investigate the properties of dust in their host galaxies. We jointly infer the dust law RV population distributions at the SED level in high- and low-mass galaxies simultaneously with dust-independent, intrinsic differences. We find an intrinsic mass step of −0.049 ± 0.016 mag, at a significance of 3.1σ, when allowing for a constant intrinsic, achromatic magnitude offset. We additionally apply a model allowing for time- and wavelength-dependent intrinsic differences between SNe Ia in different mass bins, finding ∼2σ differences in magnitude and colour around peak and 4.5σ differences at later times. These intrinsic differences are inferred simultaneously with a difference in population mean RV of ∼2σ significance, demonstrating that both intrinsic and extrinsic differences may play a role in causing the host galaxy mass step. We also consider a model which allows the mean of the RV distribution to linearly evolve with redshift but find no evidence for any evolution – we infer the gradient of this relation ηR = −0.38 ± 0.70. In addition, we discuss in brief a new, GPU-accelerated python implementation of bayesn suitable for application to large surveys which is publicly available and can be used for future cosmological analyses; this code can be found here: https://github.com/bayesn/bayesn.

Exploring late-time cosmic acceleration: A study of a linear [formula omitted] cosmological model using observational data

Understanding the evolution of dark energy poses a significant challenge in modern cosmology, as it is responsible for the universe’s accelerated expansion. In this study, we focus on a specific f(T) cosmological model and analyze its behavior using observational data, including 31 data points from the CC dataset, 1048 points from the Pantheon SNe Ia samples, and 6 points from the BAO dataset. By considering a linear f(T) model with an additional constant term, we derive the expression for the Hubble parameter as a function of cosmic redshift for non-relativistic pressureless matter. We obtain the best-fit values for the Hubble constant, H0, and the model parameters α and β, indicating a stable model capable of explaining late-time cosmic acceleration without invoking a dark energy component. This is achieved through modifying field equations to account for the observed accelerated expansion of the universe.