Light Curve Parameters Research Articles

ZTF SN Ia DR2: Simulations and volume-limited sample

ı ı tre diagram is a key tool for addressing observational systematics, such as the Malmquist bias. As the distance modulus of SNe Ia is derived from the fit of their light curves, a robust simulation framework is required. In this paper, we present the performances of the simulation framework skysurvey with the aim to reproduce the Zwicky Transient Facility (ZTF) SN Ia DR2, which covers the first phase of the ZTF and ran from March 2018 to December 2020. The ZTF SN Ia DR2 sample corresponds to almost 3000 classified SNe Ia of cosmological quality. We simulated individual light curves of the ZTF SN Ia DR2 sample to confirm the validity of the framework while taking the observing conditions and instrument performances into account. After the ZTF SN Ia DR2 selection criteria were applied, we found that the simulated fluxes and associated uncertainties agre well with the measured uncertainties when the sky-noise deduced from the observed science magnitude limits is corrected for by a factor $1.23$ for the g band, $1.17$ for the r band, and $1.20$ for the i band. In addition, we accounted for an error floor of $2.5 %$, $3.5 %$, and $6 %$ of the flux level in the g, r, and i bands, respectively. Furthermore a redshift dependence of the SALT2 light-curve parameters (stretch and colour) was conducted to deduce the redshift limit that defines a volume-limited sample, that is, an unbiased SNe Ia sample. We found that the ZTF SN Ia DR2 volume-limited sample is characterized by z ≤ 0.06. This volume-limited sample of about 1000 SNe Ia is unique, and an astrophysical analysis can be carried out based on it, or the standardisation procedure can be tested with unprecedented precision (these analyses are presented in companion papers).

Cobalt tungstate nanoparticles (CoWO4 NPs) affect the photosynthetic performance of the green microalga Raphidocelis subcapitata.

Innovative applications of cobalt tungstate nanoparticles (CoWO4 NPs) are directly linked to their increased production and consumption, which can consequently increase their release into aquatic ecosystems and the exposure of organisms. Microalgae are autotrophic organisms that contribute directly to global primary productivity and provide oxygen for maintaining many organisms on Earth. In this paper, we assessed the toxicity of CoWO4 NPs when in contact with the freshwater microalga Raphidocelis subcapitata (Chlorophyceae). To this end, we assessed algal growth, reactive oxygen species (ROS) production and photosynthetic performance. Our results show that the NPs inhibited the growth of algal cells from 42.37 mg L-1, significantly induced ROS production in the first hours of exposure (1 h) at all concentrations and directly compromised the photosynthetic activity, reinforcing that the oxygen-evolving complex (OEC) is one of the main targets of NPs and that the light curve parameters were the most sensitive endpoints. We observed reductions in the maximum relative electron transport rate (rETRmax) of around 53% and decreases in the saturating irradiance (Ek) of around 40%, which demonstrated that the NPs not only compromised the photosynthetic activity, but also decreased the ability of algal cells to tolerate high light intensities. Our results also highlight that Co was mostly particulate and that the dissolved fraction represented only ∼8% at the lowest concentration and ∼ 0.70% at the highest concentration of CoWO4 NPs, suggesting that the toxicity observed was caused by the NPs. CoWO4 NPs exhibited a high negative surface charge of -33mV in L.C. Oligo medium. The polydispersity index (PdI) varied from 0.22 to 0.45, while the hydrodynamic size ranged from 217.8 ± 11.36 to 503.43 ± 32.78 nm, indicating greater aggregation in this medium. This study elucidates how the CoWO4 NPs interact with R. subcapitata¸ resulting in changes mainly in its photosynthetic performance.

Metallicity of RR Lyrae stars from the Gaia Data Release 3 catalogue computed with Machine Learning algorithms

Abstract We present new P − φ31 − [Fe/H] and P − φ31 − A2 − [Fe/H] relations for fundamental-mode (RRab) and first-overtone mode (RRc) RR Lyrae stars (RRLs), respectively. The relations were calibrated based on pulsation periods and Fourier parameters of the RRL light curves in the Gaia G-band published in the Gaia Data Release 3 (DR3), and accurate spectroscopically measured metallicities available in the literature. We apply the feature selection algorithm to identify the most relevant parameters for the determination of metallicity. To fit the relations, we used the Bayesian approach, which allowed us to carefully take into account uncertainties in various parameters and the intrinsic scatter of the relations. The root mean squared errors of the predicted metallicity values in the training samples are 0.28 dex and 0.21 dex for RRab and RRc stars, respectively, comparable with the typical uncertainty of low/intermediate resolution spectroscopic metallicity measurements. We applied the new relations to measure individual metallicities and distances to ∼ 134,000 RRLs from the Gaia DR3 catalogue, as well as mean metallicities and distances to 38 Milky Way globular clusters. We also estimate the mean metallicity and distance to the Large Magellanic Cloud (LMC) and Small Magellanic Cloud (SMC): [Fe/H]LMC = −1.63 ± 0.36 and μLMC = 18.55 ± 0.18 mag, [Fe/H]SMC = −1.86 ± 0.36 dex and μSMC = 19.01 ± 0.17 mag, respectively, in excellent agreement with previous measurements.

Impacts of phosphorus limitation in the toxicity of environmental concentrations of lead and zinc in Raphidocelis subcapitata (Chlorophyceae)

AbstractMicroalgal metabolism is affected by the surrounding environment and nutrients such as phosphorus (P) and nitrogen (N) are essential for optimal metabolism, as well as trace amounts of essential metals such as zinc (Zn); although in higher doses than required, Zn can be toxic. Lead (Pb) is a non-essential metal that can harm organisms from different trophic levels. In the environment, algae are exposed to several stressors simultaneously and adapt their metabolism. In the present study, we evaluated P limitation combined with environmental concentrations of Zn or Pb to the freshwater microalga Raphidocelis subcapitata regarding growth, pigments production, and photosynthetic parameters. Our results indicate that P limitation affected the growth, pigments production, relative maximum electron transport rate (rETRmax), and saturation irradiance; while Pb altered growth, pigments production, and maximum quantum yield; and Zn affected pigment production, photochemical and non-photochemical quenching, and rETRmax. However, the combination of metal and P limitation resulted in synergistic responses, i.e., higher damages than the isolated stressors, in growth, maximum and effective quantum yield, and in the rapid light curve parameters. On the other hand, antagonism, i.e., lower damages than isolated stressors, was observed in pigments production and non-photochemical quenching, suggesting that algae activated defense mechanisms to cope with both stressors simultaneously. In addition, our results indicate an algal metabolism adjustment to P limitation and highlight the importance of considering physicochemical water characteristics when defining regulations of acceptable levels of metals in aquatic ecosystems.

ZTF SN Ia DR2: Study of Type Ia supernova light-curve fits

Type Ia supernova (SN Ia) cosmology relies on the estimation of light-curve parameters to derive precision distances, which are used to infer cosmological parameters such as $H_0$, $ and $w$. The empirical SALT2 light-curve modeling that relies on only two parameters, a stretch $x_1$ and a color $c$, has been used by the community for almost two decades. We study the ability of the SALT2 model to fit the nearly 3000 cosmology-grade SN Ia light curves from the second release of the Zwicky Transient Facility (ZTF) cosmology science working group. While the ZTF data were not used to train SALT2, the algorithm models the ZTF SN Ia optical light curves remarkably well, except for light-curve points prior to $-10$ d from maximum, where the training critically lacks data. We find that the light-curve fitting is robust against the considered choice of phase range, but we show that the $ $ d range is optimal in terms of statistics and accuracy. We do not detect any significant features in the light-curve fit residuals that could be connected to the host environment. Potential systematic uncertainties associated tp population differences related to the SN Ia host properties might thus not be accountable for by the inclusion of addition of light-curve parameters. However, a small but significant inconsistency between residuals of blue and red SN Ia strongly suggests the existence of a phase-dependent color term, with potential implications for the use of SNe Ia in precision cosmology. We thus encourage further work in this area to explore this possibility, and we emphasize that SN Ia cosmology must include a SALT2 retraining to accurately model the light curves and avoid biasing the derivation of cosmological parameters.

ZTF SN Ia DR2: The spectral diversity of Type Ia supernovae in a volume-limited sample

More than 3000 spectroscopically confirmed Type Ia supernovae (SNe Ia) are presented in the second data release (DR2) of the Zwicky Transient Facility survey. In this paper we detail the spectral properties of 482 SNe Ia near maximum light, up to a redshift limit of z leq 0.06. We measured the velocities and pseudo-equivalent widths (pEW) of key spectral features ( and and investigated the relation between the properties of the spectral features and the photometric properties from the SALT2 light-curve parameters as a function of spectroscopic sub-class. We discuss the non-negligible impact of host galaxy contamination on SN Ia spectral classifications, and we investigate the accuracy of spectral template matching of the DR2 sample. We define a new subclass of underluminous SNe Ia (04gs-like) that lie spectroscopically between normal SNe Ia and transitional 86G-like SNe Ia (stronger than normal SNe Ia, but significantly weaker features than 86G-like SNe). We model these 04gs-like SN Ia spectra using the radiative-transfer spectral synthesis code tardis and show that cooler temperatures alone are unable to explain their spectra; some changes in elemental abundances are also required. However, the broad continuity in spectral properties seen from bright (91T-like) to faint normal SN Ia, including the transitional and 91bg-like SNe Ia, suggests that variations within a single explosion model may be able to explain their behaviour.

Cosmological foundations revisited with Pantheon+

Abstract We reanalyse the Pantheon+ supernova catalogue to compare a cosmology with non-FLRW evolution, the timescape cosmology, with the standard ΛCDM cosmology. To this end, we analyse the Pantheon+ for a geometric comparison between the two models. We construct a covariance matrix to be as independent of cosmology as possible, including independence from the FLRW geometry and peculiar velocity with respect to FLRW average evolution. This framework goes far beyond most other definitions of model independence. We introduce new statistics to refine Type Ia supernova (SNe Ia) light-curve analysis. In addition to conventional galaxy correlation functions used to define the scale of statistical homogeneity we introduce empirical statistics which enables refined analysis of the distribution biases of SNe Ia light-curve parameters βc and $\alpha {x_{\lower2pt\hbox{$\scriptstyle 1$}}}$. For lower redshifts, the Bayesian analysis highlights important features attributable to the increased number of low-redshift supernovae, the artefacts of model-dependent light-curve fitting and the cosmic structure through which we observe supernovae. This indicates the need for cosmology-independent data reduction to conduct a stronger investigation of the emergence of statistical homogeneity and to compare alternative cosmologies in light of recent challenges to the standard model. Dark energy is generally invoked as a place-holder for new physics. For the first time, we find evidence that the timescape cosmology may provide a better overall fit than ΛCDM and that its phenomenology may help disentangle other astrophysical puzzles. Our from-first-principles reanalysis of Pantheon+ supports future deeper studies between the interplay of matter and nonlinear spacetime geometry in a data-driven setting.

Deep drilling in the time domain with DECam – II: characterizing the light curves of candidates in the extragalactic fields

ABSTRACT In this second paper on the DECam deep-drilling field (DDF) program, we release 2020 optical $gri$-band light curves for transients and variables in the extragalactic COSMOS and ELAIS fields based on time series observations with a 3-d cadence from semester 2021A through 2023A. In order to demonstrate the wide variety of time domain events detected by the program and encourage others to use the data set, we characterize the sample by presenting a brief analysis of the light-curve parameters such as time span, amplitude, and peak brightness. We also present preliminary light-curve categorizations, and identify potential stellar variables, active galactic nuclei, tidal disruption events, supernovae (SNe) (such as Type Ia, Type IIP, superluminous, and gravitationally lensed SNe), and fast transients. Where relevant, the number of identified transients is compared to the predictions of the original proposal. We also discuss the challenges of analyzing DDF data in the context of the upcoming Vera C. Rubin Observatory and its Legacy Survey of Space and Time, which will include DDFs. Images from the Dark Energy Camera DDF program are available without proprietary period and the light curves presented in this work are publicly available for analysis.

Use of light response curve parameters to estimate gross primary production capacity from chlorophyll indices of global observation satellite and flux data

The photosynthetic rate has a nonlinear relationship with PAR during the day. We previously developed an algorithm for estimating GPP capacity, which is defined GPP under low-stress condition, using light response curves (LRCs). In this study, we studied the characteristics of LRC parameters of the initial slope and the maximum gross photosynthesis rate (Pmax), and formulas to calculate Pmax from the relationship between the chlorophyll index of the green and near-infrared (NIR) bands (CIgreen) and the GPP capacity at PAR = 2000 μmol m−2 s−1 (GP2000) for nine vegetation types spanning tropical to subarctic climates on the Eurasian and North American continents using eddy covariance flux measurements and Moderate Resolution Imaging Spectrometer (MODIS) data. The slope of the relationship between CIgreen and GP2000 was highest for sites dominated by herbaceous plants such as open shrubland, savanna, and cropland (rice paddy); it was lower at sites dominated by woody plants. The yearly GPP/GPP capacity ratio was close to one in flux data. When the method was applied to satellite data, the daily GPP capacity exhibited a similar seasonal pattern to that of the Flux GPP and MODIS GPP products. Under high dryness conditions, Flux GPP showed the drop from the GPP capacity estimated from CIgreen and diurnal PAR data around noon, and they were nearly identical during the early morning and late afternoon. The instantaneous GPP capacity could be considered the baseline of the instantaneous GPP with stress-free conditions and important for quantifying midday depression at the sub-day scale.

Measuring the ejecta velocities of type Ia supernovae from the pan-STARRS1 medium deep survey

ABSTRACT There is growing evidence that Type Ia supernovae (SNe Ia) may originate from multiple explosion channels. Previous studies have indicated that the ejecta velocity of SNe Ia is one powerful tool to discriminate between different channels. In this work, we study ∼400 confirmed SNe Ia discovered by the Pan-STARRS1 Medium Deep Survey (PS1-MDS), and obtain a sample of ∼50 SNe Ia that have near-peak $\mathrm{Si}\, {\small II}\, \lambda 6355$ velocity ($v_{\mathrm{Si}\, {\small II}}$) measurements. We investigate the relationships between $v_{\mathrm{Si}\, {\small II}}$ and various parameters, including SN light-curve width, colour, host galaxy properties, and redshift. No significant trends are identified between $v_{\mathrm{Si}\, {\small II}}$ and light-curve parameters. Regarding the host-galaxy properties, we see a significant trend that high-velocity (HV) SNe Ia ($v_{\mathrm{Si}\, {\small II}}\gtrsim 12000$ km s$^{-1}$) tend to reside in more massive galaxies compared to normal velocity (NV) SNe Ia ($v_{\mathrm{Si}\, {\small II}}\lt 12000$ km s$^{-1}$) when combining both the PS1-MDS data set and those from previous low-z studies. While we do not see a significant trend between $v_{\mathrm{Si}\, {\small II}}$ and redshift, HV SNe Ia appear to be more prevalent in low-z samples than in high-z samples. We discuss several possibilities that could potentially contribute to this trend. Furthermore, we investigate the potential bias on SN Ia distances and find no significant difference in Hubble residuals between HV and NV subgroups.

Extrapolation of Type Ia Supernova Spectra into the Near-infrared Using Principal Component Analysis

We present a method of extrapolating the spectroscopic behavior of Type Ia supernovae (SNe Ia) in the near-infrared (NIR) wavelength regime up to 2.30 μm using optical spectroscopy. Such a process is useful for accurately estimating K-corrections and other photometric quantities of SNe Ia in the NIR. A principal component analysis is performed on data consisting of Carnegie Supernova Project I & II optical and NIR FIRE spectra to produce models capable of making these extrapolations. This method differs from previous spectral template methods by not parameterizing models strictly by photometric light-curve properties of SNe Ia, allowing for more flexibility of the resulting extrapolated NIR flux. A difference of around −3.1% to −2.7% in the total integrated NIR flux between these extrapolations and the observations is seen here for most test cases including Branch core-normal and shallow-silicon subtypes. However, larger deviations from the observation are found for other tests, likely due to the limited high-velocity and broad-line SNe Ia in the training sample. Maximum-light principal components are shown to allow for spectroscopic predictions of the color-stretch light-curve parameter, s BV, within approximately ±0.1 units of the value measured with photometry. We also show these results compare well with NIR templates, although in most cases the templates are marginally more fitting to observations, illustrating a need for more concurrent optical+NIR spectroscopic observations to truly understand the diversity of SNe Ia in the NIR.

Cosmological prediction of the CSST Ultra Deep Field Type Ia supernova photometric survey

ABSTRACT Type Ia supernova (SN Ia) as a standard candle is an ideal tool to measure cosmic distance and expansion history of the Universe. Here, we investigate the SN Ia photometric measurement in the China Space Station Telescope Ultra Deep Field (CSST-UDF) survey, and study the constraint power on the cosmological parameters, such as the equation of state of dark energy. The CSST-UDF survey is expected to cover a 9 deg2 sky area in 2 yr with 250 s × 60 exposures for each band. The magnitude limit can reach i ≃ 26 AB mag for 5σ point source detection with a single exposure. We generate light-curve mock data for SNe Ia and different types of core-collapse SNe (CCSNe). sncosmo is chosen as the framework by utilizing the salt3 model to simulate SN Ia data. After selecting high-quality data and fitting the light curves, we derive the light-curve parameters and identify CCSNe as contamination, resulting in ∼2200 SNe with an $\sim\!\! 7{{\ \rm per\, cent}}$ CCSN contamination rate. We adopt a calibration method similar to Chauvenet’s criterion, and apply it to the distance modulus data to further reduce the contamination. We find that this method is effective and can suppress the contamination fraction to $\sim\!\! 3.5{{\ \rm per\, cent}}$ with 2012 SNe Ia and 73 CCSNe. In the cosmological fitting stage, we did not distinguish between SNe Ia and CCSNe. We find that the constraint accuracies on ΩM, ΩΛ, and w are about two times better than the current SN surveys, and they could be further improved by a factor of ∼1.4 if including the baryon acoustic oscillation data from the CSST spectroscopic wide-field galaxy survey.

Tracing back the birth environments of Type Ia supernova progenitor stars: a pilot study based on 44 early-type host galaxies

ABSTRACT The environmental dependence of Type Ia supernova (SN Ia) luminosities is well established, and efforts are being made to find its origin. Previous studies typically use the currently observed status of the host galaxy. However, given the delay time between the birth of the progenitor star and the SN Ia explosion, the currently observed status may differ from the birth environment of the SN Ia progenitor star. In this paper, employing the chemical evolution and accurately determined stellar population properties of 44 early-type host galaxies, we, for the first time, estimate the SN Ia progenitor star birth environment, specifically [Fe/H]Birth and [α/Fe]Birth. We show that [α/Fe]Birth has a $30.4^{\text{+10.6}}_{-10.1}{{\ \rm per\ cent}}$ wider range than the currently observed [α/Fe]Current, while the range of [Fe/H]Birth is not statistically different ($17.9^{\text{+26.0}}_{-27.1}{{\ \rm per\ cent}}$) to that of [Fe/H]Current. The birth and current environments of [Fe/H] and [α/Fe] are sampled from different populations (p-values of the Kolmogorov–Smirnov test <0.01). We find that light-curve fit parameters are insensitive to [Fe/H]Birth (<0.9σ for the non-zero slope), while a linear trend is observed with Hubble residuals (HRs) at the 2.4σ significance level. With [α/Fe]Birth, no linear trends (<1.1σ) are observed. Interestingly, we find that [α/Fe]Birth clearly splits the SN Ia sample into two groups: SN Ia exploded in [α/Fe]Birth-rich or [α/Fe]Birth-poor environments. SNe Ia exploded in different [α/Fe]Birth groups have different weighted-means of light-curve shape parameters: 0.81 ± 0.33 (2.5σ). They are thought to be drawn from different populations (p-value = 0.01). Regarding SN Ia colour and HRs, there is no difference (<1.0σ) in the weighted-means and distribution (p-value > 0.27) of each [α/Fe]Birth group.

Keck Infrared Transient Survey. I. Survey Description and Data Release 1

We present the Keck Infrared Transient Survey, a NASA Key Strategic Mission Support program to obtain near-infrared (NIR) spectra of astrophysical transients of all types, and its first data release, consisting of 105 NIR spectra of 50 transients. Such a data set is essential as we enter a new era of IR astronomy with the James Webb Space Telescope (JWST) and the upcoming Nancy Grace Roman Space Telescope (Roman). NIR spectral templates will be essential to search JWST images for stellar explosions of the first stars and to plan an effective Roman SN Ia cosmology survey, both key science objectives for mission success. Between 2022 February and 2023 July, we systematically obtained 274 NIR spectra of 146 astronomical transients, representing a significant increase in the number of available NIR spectra in the literature. Here, we describe the first release of data from the 2022A semester. We systematically observed three samples: a flux-limited sample that includes all transients <17 mag in a red optical band (usually ZTF r or ATLAS o bands); a volume-limited sample including all transients within redshift z < 0.01 (D ≈ 50 Mpc); and an SN Ia sample targeting objects at phases and light-curve parameters that had scant existing NIR data in the literature. The flux-limited sample is 39% complete (60% excluding SNe Ia), while the volume-limited sample is 54% complete and is 79% complete to z = 0.005. Transient classes observed include common Type Ia and core-collapse supernovae, tidal disruption events, luminous red novae, and the newly categorized hydrogen-free/helium-poor interacting Type Icn supernovae. We describe our observing procedures and data reduction using PypeIt, which requires minimal human interaction to ensure reproducibility.

BrightsightNet: A lightweight progressive low-light image enhancement network and its application in “Rainbow” maglev train

To address the low-light image (LLI) problem in train driving scenarios, this paper proposes a progressive and lightweight network called BrightsightNet for LLI enhancement. First, to overcome the problem of insufficient local exposure level, two structurally identical light curve parameter estimation sub-networks are used for light enhancement in turn. Second, for real-time inference, an efficient feature extraction operator is proposed that combines depth-separable convolution and attention mechanism. Third, the overall network uses encoder–decoder architecture. For the encoder, the output features of the three layers are fused through skip connections to form an information-rich feature map. For the decoder, a hierarchical decoding approach is used to predict the light curve parameters through the three convolution layers sequentially. Experimental results show that BrightsightNet achieves a user study score (USR) of 4.43 on the proposed dataset, outperforming Zero-DCE++, SCI, RetinexDIP, and RUAS by 0.51, 0.86, 0.64, and 1.39, respectively. Moreover, BrightsightNet has parameters of only 2.6K and a single inference time of 0.052 s, which is an innovative and practical solution for low-light image enhancement in train driving scenarios, contributing to safer and more reliable train operations.

Concerning the Verity of the MMRD Relation for Novae

It has long been claimed that novae reaching the highest luminosity at the peak of their eruptions appear to fade the fastest from maximum light. The relationship between peak brightness and fade rate is known as the Maximum-Magnitude, Rate-of-Decline (MMRD) relation. Lightcurve parameters for the most recent sample of M31 recurrent novae are presented and used to buttress the case that the observed MMRD relation can be explained as a consequence of observational selection effects coupled with expectations from standard nova models.

Two-population Bayesian hierarchical model of Type Ia supernovae

ABSTRACT The currently used standardization of Type Ia supernovae results in Hubble residuals whose physical origin is unaccounted for. Here, we present a complete physical interpretation of the Hubble residuals based on a novel Bayesian hierarchical model of Type Ia supernovae in which latent variables describing intrinsic and extrinsic (dust related) supernova properties originate from two supernova populations. Fitting the model to SALT2 light-curve parameters of supernovae in the Hubble flow we find strong (4σ) evidence for the presence of two overlapping, but distinct, populations differentiated primarily by their mean SALT2 shape parameter (stretch) x1. Supernovae from the population with predominantly slow decliners (higher average x1) are found to be intrinsically bluer (mean SALT2 colour c ≈ −0.11) and twice as reddened by dust (mean reddening E(B − V) ≈ 0.10) than those from the other population which is dominated by fast decliners (lower average x1) with c ≈ −0.04 and E(B − V) ≈ 0.05. The inferred extinction coefficient RB in both supernova populations follows a broad distribution (scatter 0.9) with a mean of 4.1, which coincides closely with the value associated with mean extinction law in the Milky Way. We also find that the supernova data favour a peaked (two-tailed) distribution of selective extinction E(B − V) over the commonly adopted exponential model. Our approach provides a complete explanation of the distribution of supernova light-curve parameters in terms of extinction properties and the above-mentioned differences between the two populations, without the need for introducing any intrinsic scatter.

GaiaData Release 3

Context.GaiaData Release 3 (DR3) provides a number of new data products that complement the early DR3 made available two years ago. Among these is the firstGaiacatalogue of eclipsing-binary candidates containing 2 184 477 sources with brightnesses from a few magnitudes to 20 mag in theGaiaG-band and covering the full sky.Aims.We present the catalogue, describe its content, provide tips for its use, estimate its quality, and show illustrative samples.Methods.Candidate selection is based on the results of variable object classification performed within theGaiaData Processing and Analysis Consortium. Candidates are then further filtered using eclipsing-binary-tailored criteria based on theG-band light curves. To find the orbital period, a large ensemble of trial periods is first acquired using three distinct period-search methods applied to the cleanedGlight curve of each source. TheGlight curve is then modelled with up to two Gaussians and a cosine for each trial period. The best combination of orbital period and geometric model is finally selected using Bayesian model comparison based on the BIC. A global ranking metric is provided to rank the quality of the chosen model between sources. The catalogue is restricted to orbital periods larger than 0.2 days.Results.Of ∼600 000 available crossmatches, about 530 000 of the candidates are classified as eclipsing binaries in the literature as well, and 93% of them have published periods compatible with theGaiaperiods. Catalogue completeness is estimated to be between 25% and 50%, depending on the sky region, relative to the OGLE4 catalogues of eclipsing binaries towards the Galactic Bulge and the Magellanic Clouds. The analysis of an illustrative sample of ∼400 000 candidates with significant parallaxes shows properties in the observational Hertzsprung-Russell diagram as expected for eclipsing binaries. The subsequent analysis of a subsample of detached bright candidates provides further hints for the exploitation of the catalogue. We also address the observed lack of short-period (less than a day) systems in the Magellanic Cloud in comparison to Galactic systems. The orbital periods, light-curve model parameters, and global rankings are all published in the catalogue with their related uncertainties where applicable.Conclusions.ThisGaiaDR3 catalogue of eclipsing-binary candidates constitutes the largest catalogue to date in terms of number of sources, sky coverage, and magnitude range.

A Linear Relation between the Color Stretch s BV and the Rising Color Slope of Type Ia Supernovae

Using data from the Complete Nearby (redshift z host < 0.02) sample of Type Ia Supernovae (CNIa0.02), we find a linear relation between two parameters derived from the B − V color curves of Type Ia supernovae: the color stretch s BV and the rising color slope after the peak, and this relation applies to the full range of s BV . The s BV parameter is known to be tightly correlated with the peak luminosity, especially for fast decliners (dim Type Ia supernovae), and the luminosity correlation with s BV is markedly better than with the classic light-curve width parameters such as Δm 15(B). Thus, our new linear relation can be used to infer peak luminosity from . Unlike s BV (or Δm 15(B)), the measurement of does not rely on a well-determined time of light-curve peak or color maximum, making it less demanding on the light-curve coverage than past approaches.

A multiphase study of theoretical and observed light curves of classical Cepheids in the Magellanic Clouds

ABSTRACTWe present an analysis of the theoretical and observed light-curve parameters of the fundamental mode (FU) classical Cepheids in the Magellanic Clouds in V- and I- photometric bands. The state-of-the-art 1D non-linear radial stellar pulsation (RSP) code in mesa (mesa-rsp) has been utilized to generate the theoretical light curves using four sets of convection parameters. Theoretical light curves with two chemical compositions: Z = 0.008 and Z = 0.004 appropriate for the Large Magellanic Cloud (LMC) and Small Magellanic Cloud (SMC), respectively, covered a wide range of periods ($3\lt P (\rm {d})\lt 32$). The observed light curves are taken from the OGLE-IV data base. We compare theoretical and observed Fourier parameters (FPs), and investigate the period–luminosity (PL), period–colour (PC), and amplitude–colour (AC) relations as a function of pulsation phase for short (log P &amp;lt; 1), long (log P &amp;gt; 1), and all periods. The multiphase relations obtained from theoretical and observed light curves in the PL/PC/AC plane are found to be dynamic in nature, with the effect more pronounced at Φ ∼ 0.75–0.85. Furthermore, a contrasting behaviour of the theoretical/observed multiphase PL and PC relations between the short and long periods has been found for both LMC and SMC. The analysis shows that multiphase PL relations are more stringent to test the models with observations over the FPs. Distances to the LMC/SMC determined using long period Cepheids are found to be in good agreement with the literature values when the term R21 is added to the PL relation.