arXiv subjects

M. G. Dainotti

Publications and source records attributed to M. G. Dainotti.

At least 19 recordsLinked to original sources

arXiv2026

Multi-Model Framework for Reconstructing Gamma-Ray Burst Light Curves

Mitigating data gaps in Gamma-ray bursts (GRBs) light curves (LCs) is crucial for cosmological research, enhancing the precision of parameters, assuming perfect satellite conditions for complete LC coverage with no gaps. This analysis improves the applicability of the two-dimensional Dainotti relation, which connects the rest-frame end time of the plateau emission (Ta) and its luminosity (La), derived from the fluxes (Fa). The study expands on a previous 521 GRB sample by incorporating seven models: Deep Gaussian Process (DGP), Temporal Convolutional Network (TCN), Hybrid CNN with Bidirectional Long Short-Term Memory (CNN-BiLSTM), Bayesian Neural Network (BNN), Polynomial Curve Fitting, Isotonic Regression, and Quartic Smoothing Spline (QSS). Results indicate that QSS significantly reduces uncertainty across parameters: 43.5% for log Ta, 43.2% for log Fa, and 48.3% for alpha, outperforming the other models where alpha denotes the slope post-plateau based on Willingale 2007 functional form. The Polynomial Curve Fitting model demonstrates moderate uncertainty reduction across parameters, while CNN-BiLSTM has the lowest outlier rate for alpha at 0.77%. These models broaden the application of machine-learning techniques in GRB LC analysis, enhancing uncertainty estimation and parameter recovery, and complement traditional methods like the Attention U-Net and Multilayer Perceptron (MLP). These advancements highlight the potential of GRBs as cosmological probes, supporting their role in theoretical model discrimination via LC parameters, serving as standard candles, and facilitating GRB redshift predictions through advanced machine-learning approaches.

astro-ph.HE↗

arXiv2026

Gamma-Ray Burst Light Curve Reconstruction: A Comparative Machine and Deep Learning Analysis

Gamma-Ray Bursts (GRBs), observed at high-z, are probes of the evolution of the Universe and can be used as cosmological tools. Thus, we need correlations with small dispersion among key parameters. To reduce such a dispersion, we mitigate gaps in light curves (LCs), including the plateau region, key to building the two-dimensional Dainotti relation between the end time of plateau emission (Ta) and its luminosity (La). We reconstruct LCs using nine models: Multi-Layer Perceptron (MLP), Bi-Mamba, Fourier Transform, Gaussian Process-Random Forest Hybrid (GP-RF), Bidirectional Long Short-Term Memory (Bi-LSTM), Conditional GAN (CGAN), SARIMAX-based Kalman filter, Kolmogorov-Arnold Networks (KANs), and Attention U-Net. These methods are compared to the Willingale model (W07) over a sample of 521 GRBs. MLP and Attention U-Net outperform other methods, with MLP reducing the plateau parameter uncertainties by 37.2% for log Ta, 38.0% for log Fa, and 41.2% for alpha (the post-plateau slope in the W07 model), achieving the lowest 5-fold cross-validation (CV) mean squared error (MSE) of 0.0275. Attention U-Net achieved the lowest uncertainty of parameters, a 37.9% reduction in log Ta, a 38.5% reduction in log Fa and a 41.4% reduction in alpha, but with a higher MSE of 0.134. Although Attention U-Net achieves the largest uncertainty reduction, the MLP attains the lowest test MSE while maintaining comparable uncertainty performance, making it the more reliable model. The other methods yield MSE values ranging from 0.0339 to 0.174. These improvements in parameter precision are needed to use GRBs as standard candles, investigate theoretical models, and predict GRB redshifts through machine learning.

astro-ph.HE↗

arXiv2026

On the Metric $f(R)$ gravity Viability in Accounting for the Binned Supernovae Data

In this work, two models of metric $f(R)$ gravity in the Jordan frame are investigated as a dynamical description of the late-time cosmic expansion using binned Type Ia Supernovae data. The aim is to provide an explanation for the effective running of the Hubble constant observed in both the binned Pantheon Sample and the Master Sample. To this end, the effective running Hubble constant $\mathcal{H}(z)$ is defined as the ratio between the modified Hubble parameter and that of the $Λ$CDM, multiplied by $H_0$. $\mathcal{H}(z)$ serves as a diagnostic tool to capture deviations from the $Λ$CDM model. The first model used is a general representation of metric $f(R)$ gravity in which the gravitational Lagrangian is encoded in an effective redshift-dependent function that mimics the evolution of the Hubble parameter. This function can be approximated by a second-order Taylor expansion at low redshift due to the limited redshift range covered by the Supernovae data. While this general formulation yields a phenomenological fit compatible with that of the $Λ$CDM model for the binned Pantheon Sample, the model generically leads to the emergence of an unphysical mass of the scalar field. This issue originates from an implicit restriction imposed on the Cauchy problem for the scalar field. To address this limitation, following previous studies, an additional condition on the modified Friedmann equation is introduced, enabling a fully consistent reformulation of the dynamics. It is clarified that this additional condition has a precise dynamical origin, being necessary to restore a consistent Cauchy problem and to ensure a finite, positive scalar field mass. The resulting framework not only preserves the agreement with binned Supernova Ia data, but also provides a physical justification for the additional condition adopted in earlier analyses of late-time cosmological dynamics.

gr-qc↗

arXiv2025

The effective running Hubble constant in SNe Ia as a marker for the dark energy nature

We propose a new method that reveal the nature of dark energy (DE) evolution. Specifically, the method consists of studying the evolving trend regarding the effective running Hubble constant: when it increases, it indicates a quintessence nature, and when it decreases, it reveals a phantom behavior. Within the framework of the dark energy models we analyze three parameterizations: the $w$CDM model, a reduced Chevallier-Polarski-Linder (CPL) model and a new theoretical model based on the possible creation of dark energy by the time-varying gravitational field of the expanding Universe. For each DE model, we construct a theoretical effective running Hubble constant, i.e. a function of the redshift, which highlights the difference between modified dynamics and the $Λ$CDM-one. Furthermore, these dark energy models are compared to the phenomenological model of a decreasing trend of the Hubble constant as a function of the redshift, called the power-law model (PL) and the $Λ$CDM one. These three theoretical functions are fitted against the binned SNe Ia data samples, i.e. the Pantheon and the Master samples, the latter being a collection of SNe Ia from 4 catalogs: Dark Energy Survey (DES), PantheonPlus, Pantheon and Joint Lightcurve Analysis (JLA), without duplicated SNe Ia, called the Master sample. The main result of our study is that the phenomenological PL model is statistically favored compared to the other proposed scenarios, both for the Pantheon and the Master samples. At this stage, the SNe Ia data do not indicate that the evolution of dark energy models among the studied ones is favored respect to the $Λ$CDM. Nevertheless, the binned Pantheon sample allows for a discrimination of the nature of dark energy at least at the $1\,σ$ level via the fit of the effective running Hubble constant.

astro-ph.CO↗

arXiv2025

A New Master Supernovae Ia sample and the investigation of the $H_0$ tension

Modern cosmological research still thoroughly debates the discrepancy between local probes and the Cosmic Microwave Background observations in the Hubble constant (\texorpdfstring{$H_0$}{H0}) measurements, ranging from 4 to 6$σ$. In the current study, we examine this tension using the Supernovae Ia (SNe Ia) data from the Pantheon, Pantheon+ (P+), Joint Lightcurve Analysis (JLA), and Dark Energy Survey, (DES) catalogs combined together into the so-called Master Sample. The sample contains 3714 SNe Ia, and is divided all of them into redshift-ordered bins. Three binning techniques are presented: the equi-population, the moving window (MW), and the equi-spacing in the \texorpdfstring{$\log-z$}{log-z}. We perform a Markov-Chain Monte Carlo analysis (MCMC) for each bin to determine the $H_0$ value, estimating it within the standard flat \texorpdfstring{$Λ$CDM}{LCDM} and the \texorpdfstring{$w_{0}w_{a}$CDM}{w0waCDM} models. These \texorpdfstring{$H_0$}{H0} values are then fitted with the following phenomenological function: \texorpdfstring{$\mathcal{H}_0(z) = \tilde{H}_0 / (1 + z)^α$}{H0(z) = H0tilde / (1 + z)^alpha}, where \texorpdfstring{$\tilde{H}_0$}{H0tilde} is a free parameter representing \texorpdfstring{$\mathcal{H}_0(z)$}{H0(z)} fitted in \texorpdfstring{$z=0$}{z=0}, and \texorpdfstring{$α$}{alpha} is the evolutionary parameter. Our results indicate a decreasing trend characterized by \texorpdfstring{$α\sim 0.01$}{alpha ~ 0.01}, whose consistency with zero ranges from $1 σ$ in 5 cases to 1 case at 3 $σ$ and 11 cases at $> 3 σ$ in several samples and configurations. Such a trend in the SNe Ia catalogs could be due to evolution with redshift for the astrophysical variables or unveiled selection biases. Alternatively, intrinsic physics, possibly the \texorpdfstring{$f(R)$}{f(R)} theory of gravity, could be responsible for this trend.

astro-ph.CO↗

arXiv2024

A doublet of cosmological models to challenge the H0 tension in the Pantheon Supernovae Ia catalog

$Λ$CDM provides a leading framework in the interpretation of modern cosmology. Nevertheless, the scientific community still struggles with many open problems in cosmology. Among the most noticeable ones, the tension in the Hubble constant $H_0$ is particularly intriguing, prompting a wide range of possible solutions. In the present work, the flat scale-free cosmology ($S$CDM) of Maeder (2017) is tested for $H_0$ tension in fits to the Pantheon sample of Supernovae Ia. The Pantheon sample is a collection of 1048 SNe Ia, which formally defines $H_0=H(0)$ by extrapolation to redshift zero of data over positive redshifts $z>0$. Here, we consider $H_{0,k}$ in fits of $S$CDM over $k$ equally sized bins of sub-samples of mean redshift $z_k$. To quantify a trend in $H_{0,k}$ with $z_k$, the results are fit by $f(z)=H'_0/(1+z)^α$ in the two parameters $H'_0$ and $α$. This approach tests for model imperfections or data biases by trends that are inconsistent with zero. Our findings show a decreasing trend inconsistent with zero at $5.3 σ$ significance, significantly more so than in $Λ$CDM. These results are further confirmed in Pantheon+. It appears that a solution to $H_0$ tension is to be found in models with a deceleration parameter $q_0<q_{0,Λ}$ below that of $Λ$CDM, rather than $q_{0,Λ} < q_{0,S}<0$ satisfied by $S$CDM.

astro-ph.CO↗

arXiv2024

Analysis of GRB Closure Relationship in Multi-wavelengths

Gamma-ray bursts (GRBs) are intense pulses of high-energy emission associated with massive stars' death or compact objects' coalescence. Their multi-wavelength observations help verify the reliability of the standard fireball model. We analyze 14 GRBs observed contemporaneously in gamma-rays by the \textit{Fermi} Large Area Telescope (LAT), in X-rays by the \textit{Swift} Telescope, and in the optical bands by \textit{Swift} and many ground-based telescopes. We study the correlation between the spectral and temporal indices using closure relations according to the synchrotron forward-shock model in the stratified medium ($n \propto r^{-k}$) with $k$ ranging from 0 to 2.5. We find that the model without energy injection is preferred over the one with energy injection in all the investigated wavelengths. In gamma-rays, we only explored the $ν> $ max\{$ν_c,ν_m$\} (SC/FC) cooling condition (where $ν_c$ and $ν_m$ are the cooling and characteristic frequencies, namely the frequencies at the spectral break). In the X-ray and optical bands, we explored all the cooling conditions, including $ν_m < ν< ν_c$ (SC), $ν_c < ν< ν_m$ (FC), and SC/FC, and found a clear preference for SC for X-rays and SC/FC for optical. Within these cooling conditions, X-rays exhibit the highest rate of occurrence for the density profile with $k = 0$, while the optical band has the highest occurrence for $k$ = 2.5 when considering no energy injection. Although we can pinpoint a definite environment for some GRBs, we find degeneracies in other GRBs.

astro-ph.HE↗

arXiv2024

Synchrotron self-Compton in a radiative-adiabatic fireball scenario: Modelling the multiwavelength observations in some Fermi/LAT bursts

Energetic GeV photons expected from the closest and the most energetic Gamma-ray bursts (GRBs) provide an unique opportunity to study the very-high-energy emission as well as the possible correlations with lower energy bands in realistic GRB afterglow models. In the standard GRB afterglow model, the relativistic homogeneous shock is usually considered to be fully adiabatic, however, it could be partially radiative. Based on the external forward-shock scenario in both stellar wind and constant-density medium. We present a radiative-adiabatic analytical model of the synchrotron self-Compton (SSC) and synchrotron processes considering an electron energy distribution with a power-law index of 1 < p < 2 and 2 $\leq$ p. We show that the SSC scenario plays a relevant role in the radiative parameter $ε$, leading to a prolonged evolution during the slow cooling regime. In a particular case, we derive the Fermi/LAT light curves together with the photons with energies $\geq$ 100 MeV in a sample of nine bursts from the second Fermi/LAT GRB catalog that exhibited temporal and spectral indices with $\geq$ 1.5 and $\approx$ 2, respectively. These events can hardly be described with closure relations of the standard synchrotron afterglow model, and also exhibit energetic photons above the synchrotron limit. We have modeled the multi-wavelength observations of our sample to constrain the microphysical parameters, the circumburst density, the bulk Lorentz factor and the mechanism responsible for explaining the energetic GeV photons.

astro-ph.HE↗

arXiv2024

An Optical Gamma-Ray Burst Catalogue with Measured Redshift PART I: Data Release of 535 Gamma-Ray Bursts and Colour Evolution

We present the largest optical photometry compilation of Gamma-Ray Bursts (GRBs) with redshifts ($z$). We include 64813 observations of 535 events (including upper limits) from 28 February 1997 up to 18 August 2023. We also present a user-friendly web tool \textit{grbLC} which allows users the visualization of photometry, coordinates, redshift, host galaxy extinction, and spectral indices for each event in our database. Furthermore, we have added a Gamma Ray Coordinate Network (GCN) scraper that can be used to collect data by gathering magnitudes from the GCNs. The web tool also includes a package for uniformly investigating colour evolution. We compute the optical spectral indices for 138 GRBs for which we have at least 4 filters at the same epoch in our sample and craft a procedure to distinguish between GRBs with and without colour evolution. By providing a uniform format and repository for the optical catalogue, this web-based archive is the first step towards unifying several community efforts to gather the photometric information for all GRBs with known redshifts. This catalogue will enable population studies by providing light curves (LCs) with better coverage since we have gathered data from different ground-based locations. Consequently, these LCs can be used to train future LC reconstructions for an extended inference of the redshift. The data gathering also allows us to fill some of the orbital gaps from Swift in crucial points of the LCs, e.g., at the end of the plateau emission or where a jet break is identified.

astro-ph.HE↗

arXiv2023

Off-axis Afterglow Closure Relations and Fermi-LAT Detected Gamma-Ray Bursts

Gamma-ray bursts (GRBs) are one of the most promising transient events for studying multi-wavelength observations in extreme conditions. Observation of GeV photons from bursts would provide crucial information on GRB physics, including the off-axis emission. The Second Gamma-ray Burst Catalog (2FLGC) was announced by the Fermi Large Area Telescope (Fermi-LAT) Collaboration. This catalog includes 29 bursts with photon energy higher than 10 GeV. While the synchrotron forward-shock model has well explained the afterglow data of GRBs, photon energies greater than 10 GeV are very difficult to interpret within this framework. To study the spectral and temporal indices of those bursts described in 2FLGC, Fraija et al. (2022a) proposed the closure relations (CRs) of the synchrotron self-Compton (SSC) emitted from an on-axis jet which decelerates in stellar-wind and the constant-density medium. In this paper, we extend the CRs of the SSC afterglow from an on-axis scenario to an off-axis, including the synchrotron afterglow radiation that seems off-axis. In order to investigate the spectral and temporal index evolution of those bursts reported in 2FLGC, we consider the hydrodynamical evolution with energy injection in the adiabatic and radiative regime for an electron distribution with a spectral index of $1<p<2$ and $2 < p$. The results show that the most likely scenario for synchrotron emission corresponds to the stellar wind whether or not there is energy injection and that the most likely scenario for SSC emission corresponds to the constant density when there is no energy injection and to the stellar wind when there is energy injection.

astro-ph.HE↗

arXiv2023

Supernovae Ia and Gamma-Ray Bursts together shed new lights on the Hubble constant tension and cosmology

The LambdaCDM model is the most commonly accepted framework in modern cosmology. However, the local measurements of the Hubble constant, H0, via the Supernovae Type Ia (SNe Ia) calibrated on Cepheids provide a value which is in significant disagreement, from 4 to 6 sigma, with the value of H0 inferred from the Cosmic Microwave Background (CMB) observed by Planck. This disagreement is the so-called Hubble constant tension. To find out the reason for this discrepancy, we analyze the behaviour of the H0 in the Pantheon sample of SNe Ia through a binning approach: we divide the Pantheon into 3 and 4 bins ordered with redshift (z), and for each of them, we estimate the H0. After the H0 estimation, we fit the H0 values with a decreasing function of z, finding out that H0 undergoes a slow decreasing trend compatible with the evolution scenario in 2.0 sigma. [...] Together with SNe Ia, more astrophysical probes such as quasars (QSO) [...] and Gamma-Ray Bursts (GRBs) [...], are needed to tackle the H0 tension. In the realm of GRB-cosmology, one of the most promising correlations is the fundamental plane relation [...]. In the context of applying this relation as a cosmological tool, we also compute how many GRBs must be gathered to reach the same precision as the SNe Ia. Since we are about two decades away from reaching such precision, we also attempt to find additional correlations for the GRBs associated with SNe Ibc that could be exploited to standardize the class of GRB-SNe Ibc in the future. We find a hint of a correlation between the GRBs' end-of-plateau optical luminosity and the SNe's rest-frame peak time, suggesting that the GRBs with the most luminous optical plateau emission are associated with SNe with the most delayed peaks in their light curves. So far, it is the fundamental plane relation to be the most promising candle for exploring the high-z universe.

astro-ph.CO↗

arXiv2023

Tensions with the flat $\boldsymbolΛ$CDM model from high-redshift cosmography

The longstanding search for the cosmological model that best describes the Universe has been made more intriguing since the recent discovery of the Hubble constant, $H_{0}$, tension observed between the value of $H_{0}$ from the Cosmic Microwave Background and from type Ia supernovae (SNe Ia). Hence, the commonly trusted flat $Λ$CDM model is under investigation. In this scenario, cosmography is a very powerful technique to investigate the evolution of the Universe without any cosmological assumption, thus revealing tensions between observational data and predictions from cosmological models in a completely model-independent way. We here employ a robust cosmographic technique based on an orthogonal logarithmic polynomial expansion of the luminosity distance to fit quasars (QSOs) alone and QSOs combined with Gamma-Ray Bursts (GRBs), SNe Ia, and Baryon Acoustic Oscillations. To apply QSOs and GRBs as probes we use, respectively, the Risaliti-Lusso relation between ultraviolet and X-ray luminosities and the ``Dainotti GRB 3D relation" among the rest-frame end time of the X-ray plateau emission, its corresponding luminosity, and the peak prompt luminosity. We also correct QSOs and GRBs for selection biases and redshift evolution and we employ both the traditional Gaussian likelihood and the newly discovered best-fit likelihoods for each probe investigated. This comprehensive analysis reveals a strong tension ($> 4 \, σ$) between our data sets and the flat $Λ$CDM model proving the power of both the cosmographic approach and high-redshift sources, such as QSOs and GRBs, which can probe the Universe at early epochs.

astro-ph.CO↗

arXiv2023

Gamma-Ray Bursts, Quasars, Baryonic Acoustic Oscillations, and Supernovae Ia: new statistical insights and cosmological constraints

The recent $\sim 4 \, σ$ Hubble constant, $H_{0}$, tension is observed between the value of $H_{0}$ from the Cosmic Microwave Background (CMB) and Type Ia Supernovae (SNe Ia). It is a decade since this tension is excruciating the modern astrophysical community. To shed light on this problem is key to consider probes at intermediate redshifts between SNe Ia and CMB and reduce the uncertainty on $H_0$. Toward these goals, we fill the redshift gap by employing Gamma-Ray Bursts (GRBs) and Quasars (QSOs), reaching $z=9.4$ and $z=7.6$, respectively, combined with Baryonic Acoustic Oscillations (BAO) and SNe Ia. To this end, we employ the ``Dainotti GRB 3D relation" among the rest-frame end time of the X-ray plateau emission, its corresponding luminosity, and the peak prompt luminosity, and the ``Risaliti-Lusso" QSO relation between ultraviolet and X-ray luminosities. We inquire the commonly adopted Gaussianity assumption on GRBs, QSOs, and BAO. With the joint sample, we fit the flat $Λ$ Cold Dark Matter model with both the Gaussian and the newly discovered likelihoods. We also investigate the impact of the calibration assumed for \textit{Pantheon} and \textit{Pantheon +} SNe Ia on this analysis. Remarkably, we show that only GRBs fulfill the Gaussianity assumption. We achieve small uncertainties on the matter density parameter $Ω_M$ and $H_0$. We find $H_0$ values compatible within 2 $σ$ with the one from the Tip of the Red Giant Branch. Finally, we show that the cosmological results are heavily biased against the arbitrary calibration choice for SNe Ia.

astro-ph.CO↗

arXiv2022

Polarization From A Radially Stratified Off-Axis GRB Outflow

While the dominant radiation mechanism gamma-ray bursts (GRBs) remains a question of debate, synchrotron emission is one of the foremost candidates to describe the multi-wavelength afterglow observations. As such, it is expected that GRBs should present some degree of polarization across their evolution - presenting a feasible means of probing these bursts' energetic and angular properties. Although obtaining polarization data is difficult due to the inherent complexities regarding GRB observations, advances are being made, and theoretical modeling of synchrotron polarization is now more relevant than ever. In this manuscript, we present the polarization for a fiduciary model where the synchrotron forward-shock emission evolving in the radiative-adiabatic regime is described by a radially stratified off-axis outflow. This is parameterized with a power-law velocity distribution and decelerated in a constant-density and wind-like external environment. We apply this theoretical polarization model for selected bursts presenting evidence of off-axis afterglow emission, including the nearest orphan GRB candidates observed by the Neil Gehrels Swift Observatory and a few Gravitational Wave (GWs) events that could generate electromagnetic emission. In the case of GRB 170817A, we require the available polarimetric upper limits in radio wavelengths to constrain its magnetic field geometry.

astro-ph.HE↗

arXiv2022

Afterglow Polarization from Off-Axis GRB Jets

As we further our studies on Gamma-ray bursts (GRBs), both on theoretical models and observational tools, more and more options begin to open for exploration of its physical properties. As transient events primarily dominated by synchrotron radiation, it is expected that the synchrotron photons emitted by GRBs should present some degree of polarization throughout the evolution of the burst. Whereas observing this polarization can still be challenging due to the constraints on observational tools, especially for short GRBs, it is paramount that the groundwork is laid for the day we have abundant data. In this work, we present a polarization model linked with an off-axis spreading top-hat jet synchrotron scenario in a stratified environment with a density profile $n(r)\propto r^ {-k}$. We present this model's expected temporal polarization evolution for a realistic set of afterglow parameters constrained within the values observed in the GRB literature for four degrees of stratification $k=0,1,1.5 {\rm \, and\,} 2$ and two magnetic field configurations with high extreme anisotropy. We apply this model and predict polarization from a set of GRBs exhibiting off-axis afterglow emission. In particular, for GRB 170817A, we use the available polarimetric upper limits to rule out the possibility of a extremely anisotropic configuration for the magnetic field.

astro-ph.HE↗

arXiv2022

Exploring the Early Afterglow Polarization of GRB 190829A

The GRB 190829A has been widely studied due to its nature and the high energy emission presented. Due to the detection of a very-high-energy component by the High Energy Stereoscopic System and the event's atypically middling luminosity, it has been categorized in a select, limited group of bursts bordering classic GRBs and nearby sub-energetic events. Given the range of models utilized to adequately characterize the afterglow of this burst, it has proven challenging to identify the most probable explanation. Nevertheless, the detection of polarization data provided by the MASTER collaboration has added a new aspect to GRB 190829A that permits us to attempt to explore this degeneracy. In this paper, we present a polarization model coupled with a synchrotron forward-shock model -- a component in all models used to describe GRB 190829A's afterglow -- in order to fit the polarization's temporal evolution with the existing upper limits ($Π< 6\%$). We find that the polarization generated from an on-axis emission is favored for strongly anisotropic magnetic field ratios, while an off-axis scenario cannot be fully ruled out when a more isotropic framework is taken into account.

astro-ph.HE↗

arXiv2022

The closure relations in optical afterglow of Gamma-Ray Bursts

Gamma-ray bursts (GRBs) are extremely high-energy events that can be observed at very high redshift. In addition to gamma rays, they can emit in X-ray, optical, and sometimes radio wavelengths. Here, following the approach in Srinivasaragavan et al. (2020); Dainotti et al. (2021b,c), and Dainotti et al (2022, submitted), we consider 82 GRBs from Dainotti et al. (2022a) that have been observed in optical wavelengths and fitted with a broken power law (BPL). We consider the relations between the spectral and temporal indices (closure relations; CRs) according to the synchrotron forward-shock model evolving in the constant-density interstellar medium (ISM; k = 0) and the stellar Wind environment (k = 2) in both slow- and fast-cooling regimes, where the density profile is defined as n is proportional to r to the power minus k. We find the nu > max nuc, nu m regime is most favored, where nu c and nu m are the cooling and characteristic frequencies, respectively. Finally, we test the 2D Dainotti correlation between the rest-frame end time of the plateau and the luminosity at that time on GRBs that fulfill the most-favored CRs. When we compare the intrinsic scatter sigma int of those 2D correlations to the scatter presented in Dainotti et al. (2020b, 2022a), we see the scatters of our correlations generally agree with the previous values within 1sigma, both before and after correction for selection bias. This new information has helped us to pinpoint subsamples of GRBs with features that could drive the GRB emission mechanism, and eventually allow for GRBs to be used as standard candles

astro-ph.HE↗

arXiv2022

The Gamma-ray Bursts fundamental plane correlation as a cosmological tool

Cosmological models and their corresponding parameters are widely debated because of the current discrepancy between the results of the Hubble constant, $H_{0}$, obtained by SNe Ia, and the Planck data from the Cosmic Microwave Background Radiation. Thus, considering high redshift probes like Gamma-Ray Bursts (GRBs) is a necessary step. However, using GRB correlations between their physical features to infer cosmological parameters is difficult because GRB luminosities span several orders of magnitude. In our work, we use a 3-dimensional relation between the peak prompt luminosity, the rest-frame time at the end of the X-ray plateau, and its corresponding luminosity in X-rays: the so-called 3D Dainotti fundamental plane relation. We correct this relation by considering the selection and evolutionary effects with a reliable statistical method, obtaining a lower central value for the intrinsic scatter, $σ_{int}=0.18 \pm 0.07$ (47.1 \%) compared to previous results, when we adopt a particular set of GRBs with well-defined morphological features, called the platinum sample. We have used the GRB fundamental plane relation alone with both Gaussian and uniform priors on cosmological parameters and in combination with SNe Ia and BAO measurements to infer cosmological parameters like $H_{0}$, the matter density in the universe ($Ω_{M}$), and the dark energy parameter $w$ for a $w$CDM model. Our results are consistent with the parameters given by the $Λ$CDM model but with the advantage of using cosmological probes detected up to $z=5$, much larger than the one observed for the furthest SNe Ia.

astro-ph.HE↗