Gamma-ray Bursts Data Set Research Articles

Cosmological transition epoch from gamma-ray burst correlations

The redshift zt and the jerk parameter jt of the transition epoch are constrained by using two model-independent approaches involving the direct expansion of the Hubble rate and the expansion of the deceleration parameter around z=zt. To extend our analysis to high-redshifts, we employ the Amati, Combo, Yonetoku and Dainotti gamma-ray burst correlations. The circularity problem is prevented by calibrating these correlations through the Bézier interpolation of the updated observational Hubble data. Each gamma-ray burst data set is jointly fit with type Ia supernovae and baryonic acoustic oscillations through a Monte Carlo analysis, based on the Metropolis-Hastings algorithm, to obtain zt, jt and the correlation parameters. The overall results are compatible with the concordance model with some exceptions. We also focus on the behaviors of the dark energy, verifying its compatibility with a cosmological constant, and the matter density Ωm and compare them with the expectations of the concordance paradigm.

Impact of cosmology on Lorentz Invariance Violation constraints from GRB time-delays

Putting constraints on a possible Lorentz Invariance Violation (LIV) from astrophysical sources such as gamma-ray bursts (GRBs) is essential for finding evidences of new theories of quantum gravity (QG) that predict an energy-dependent speed of light. This search has its own difficulties, so usually, the effect of the cosmological model is understudied, with the default model being a fixed-parameters ΛCDM.In this work, we use various astrophysical datasets to study the effect of a number of dark energy models on LIV constraints. To this end, we combine two public time-delay (TD) GRB datasets with the supernovae Pantheon dataset, several measurements of angular baryonic acoustic oscillations (BAO), the cosmic microwave background (CMB) distance prior and an optional GRB or quasars dataset. For the LIV parameter α, we find the expected from previous works average value of , corresponding to GeV for both TD datasets, with the second one being more sensitive to the cosmological model. The cosmology results in a minimum 20% deviation in our constraints on the energy. Interestingly, adding the TD points makes the DE models less-preferable statistically and shifts the value of the parameter down, making it smaller than the expected value. We observe that possible LIV measurements critically depend on the transparency of the assumptions behind the published data concerning cosmology, and taking this into account may be an important contribution in the case of possible detection.

Gamma-Ray Burst Constraints on Cosmological Models from the Improved Amati Correlation

An improved Amati correlation was constructed in ApJ 931 (2022) 50 by us recently. In this paper, we further study constraints on the ΛCDM and wCDM models from the gamma-ray bursts (GRBs) standardized with the standard and improved Amati correlations, respectively. By using the Pantheon Type Ia supernova sample to calibrate the latest A220 GRB data set, the GRB Hubble diagram is obtained model-independently. We find that at the high-redshift region (z > 1.4) the GRB distance modulus from the improved Amati correlation is larger apparently than that from the standard Amati one. The GRB data from the standard Amati correlation only give a lower bound limit on the present matter density parameter Ωm0, while the GRBs from the improved Amati correlation constrain the Ωm0 with the 68% confidence level to be and in the ΛCDM and wCDM models, respectively, which are very consistent with those given by other current popular observational data including baryon acoustic oscillation, cosmic microwave background (CMB) radiation, and so on. Once the H(z) data are added in our analysis, the constraint on the Hubble constant H 0 can be achieved. We find that two different correlations provide slightly different H 0 results but the marginalized mean values seem to be close to that from the Planck 2018 CMB radiation observations.

Do gamma-ray burst measurements provide a useful test of cosmological models?

We study eight different gamma-ray burst (GRB) data sets to examine whether current GRB measurements — that probe a largely unexplored part of cosmological redshift (z) space — can be used to reliably constrain cosmological model parameters.We use three Amati-correlation samples and five Combo-correlation samples to simultaneously derive correlation and cosmological model parameter constraints. The intrinsic dispersion of each GRB data set is taken as a goodness measurement. We examine the consistency between the cosmological bounds from GRBs with those determined from better-established cosmological probes, such as baryonic acoustic oscillation (BAO) and Hubble parameter H(z) measurements.We use the Markov chain Monte Carlo method implemented in MontePython to find best-fit correlation and cosmological parameters, in six different cosmological models, for the eight GRB samples, alone or in conjunction with BAO and H(z) data.For the Amati correlation case, we compile a data set of 118 bursts, the A118 sample, which is the largest — about half of the total Amati-correlation GRBs — current collection of GRBs suitable for constraining cosmological parameters. This updated GRB compilation has the smallest intrinsic dispersion of the three Amati-correlation GRB data sets we examined. We are unable to define a collection of reliable bursts for current Combo-correlation GRB data.Cosmological constraints determined from the A118 sample are consistent with — but significantly weaker than — those from BAO and H(z) data. They also are consistent with the spatially-flat ΛCDM model, in which dark energy is the cosmological constant Λ, as well as with dynamical dark energy models and non-spatially-flat models. Since GRBs probe a largely unexplored region of z, it is well worth acquiring more and better-quality burst data which will give a more definitive answer to the question of the title.

A Confront between Amati and Combo Correlations at Intermediate and Early Redshifts

I consider two gamma-ray burst (GRB) correlations: Amati and Combo. After calibrating them in a cosmology-independent way by employing Beziér polynomials to approximate the Observational Hubble Dataset (OHD), I perform Markov Chain Monte Carlo (MCMC) simulations within the Λ CDM and the wCDM models. The results from the Amati GRB dataset do not agree with the standard Λ CDM model at a confidence level ≥ 3 – σ . For the Combo correlation, all MCMC simulations give best-fit parameters which are consistent within 1– σ with the Λ CDM model. Pending the clarification of whether the diversity of these results is statistical, due to the difference in the dataset sizes, or astrophysical, implying the search for the most suited correlation for cosmological analyses, future investigations require larger datasets to increase the predictive power of both correlations and enable more refined analyses on the possible non-zero curvature of the Universe and the dark energy equation of state and evolution.

Tension with the flat ΛCDM model from a high-redshift Hubble diagram of supernovae, quasars, and gamma-ray bursts

In the current framework, the standard parametrization of our Universe is the so-called Lambda cold dark matter (ΛCDM) model. Recently, a ∼4σ tension with the ΛCDM model was shown to exist via a model-independent parametrization of a Hubble diagram of type Ia supernovae (SNe Ia) from the JLA survey and quasars. Model-independent approaches and independent samples over a wide redshift range are key to testing this tension and any possible systematic errors. Here we present an analysis of a combined Hubble diagram of SNe Ia, quasars, and gamma-ray bursts (GRBs) to check the agreement of the quasar and GRB cosmological parameters at high redshifts (z > 2) and to test the concordance flat ΛCDM model with improved statistical accuracy. We build a Hubble diagram with SNe Ia, quasars, and GRBs, where quasars are standardised through the observed non-linear relation between their ultraviolet and X-ray emission and GRBs through the correlation between the spectral peak energy and the isotropic-equivalent radiated energy (the so-called Amati relation). We fit the data with cosmographic models consisting of a fourth-order logarithmic polynomial and a fifth-order linear polynomial, and compare the results with the expectations from a flat ΛCDM model. We confirm the tension between the best-fit cosmographic parameters and the ΛCDM model at ∼4σ with SNe Ia and quasars, at ∼2σ with SNe Ia and GRBs, and at > 4σ with the whole SNe Ia+quasars+GRB data set. The completely independent high-redshift Hubble diagrams of quasars and GRBs are fully consistent with each other, strongly suggesting that the deviation from the standard model is not due to unknown systematic effects but to new physics.

Evolutions and Calibrations of Long Gamma-Ray-burst Luminosity Correlations Revisited

Abstract Luminosity correlations of long gamma-ray bursts (GRBs) are extensively proposed as an effective complementarity to trace the Hubble diagram of the universe at high redshifts, which is of great importance to explore properties of dark energy. Recently, several empirical luminosity correlations have been statistically proposed from GRB observations. However, to treat a GRB as the distance indicator, there are two key issues: the redshift evolution of luminosity correlations and their calibrations. In this paper, we choose the Amati relation, the correlation between the peak spectra energy and the equivalent isotropic energy of GRBs ( E p – E iso ) as an example and find that the current GRB data set implies that there could be a evolution of the luminosity correlation with respect to the redshift. Therefore, we propose an extended Amati relation with two extra redshift-dependent terms to correct the redshift evolution of the GRB relation. Second, we carefully check the reliability of the calibration method using the low-redshift GRB data. Importantly, we find that the low-redshift calibration method does not take whole correlations between Ω m and coefficients into account. Neglecting this correlation information can break the degeneracies and obtain the biased constraint on Ω m , which is very sensitive to values of parameters for the calibration. A small shift in the parameters of the “calibrated” relation could significantly change the final constraint on Ω m in the low-redshift calibration method. Finally, we simulate several GRB samples with different statistical errors and find that, in order to correctly recover the fiducial value of Ω m , using the low-redshift calibration method, we need a large number of GRB samples with high precisions.

Observational constraints on cosmological models with the updated long gamma-ray bursts

In the present work, by the help of the newly released Union2 compilation which consists of 557 Type Ia supernovae (SNIa), we calibrate 109 long Gamma-Ray Bursts (GRBs) with the well-known Amati relation, using the cosmology-independent calibration method proposed by Liang et al.. We have obtained 59 calibrated high-redshift GRBs which can be used to constrain cosmological models without the circularity problem (we call them ``Hymnium'' GRBs sample for convenience). Then, we consider the joint constraints on 7 cosmological models from the latest observational data, namely, the combination of 557 Union2 SNIa dataset, 59 calibrated Hymnium GRBs dataset (obtained in this work), the shift parameter R from the WMAP 7-year data, and the distance parameter A of the measurement of the baryon acoustic oscillation (BAO) peak in the distribution of SDSS luminous red galaxies. We also briefly consider the comparison of these 7 cosmological models.

Cosmology from gamma ray bursts

In this study we propose to use Gamma Ray Bursts (GRBs) as standard candles in order to constrain the expansion history of the universe up to redshifts of z ~ 6. In particular, we utilize the 69 GRB dataset recently compiled by Cardone et al. (2009). Performing a joint likelihood analysis of the recent supernovae type Ia (SNIa) data and the GRBs we can put constraints on the main cosmological parameters (Ωm, w). However, the use of the current GRBs to trace the Hubble relation, as an alternative to the traditionally used SNIa, can not break the degeneracy between the Ωm and the dark energy equation of state parameter.

Testing gamma-ray bursts as standard candles

Several correlations among Gamma Ray Burst (GRB) observables with available redshifts have been recently identified. Proper evaluation and calibration of these correlations may facilitate the use of GRBs as standard candles constraining the expansion history of the universe up to redshifts of $z>6$. Here we use the 69 GRB dataset recently compiled by Schaefer (astro-ph/0612285) and we test the calibration of five of the above correlations ($1:\epkk-E_\gamma$, $2:\epkk-L$, $3:\tlag-L$, $4:V-L$, $5:\trt-L$) with respect to two potential sources of systematics: Evolution with redshift and cosmological model used in the calibration. In examining the model dependence we assume flat \lcdm and vary $\omm$. Our approach avoids the circularity problem of previous studies since we do not fix $\omm$ to find the correlation parameters. Instead we simultaneously minimize $\chi^2$ with respect to both the log-linear correlation parameters $a$, $b$ and the cosmological parameter $\omm$. We find no statistically significant evidence for redshift dependence of $a$ and $b$ in any of the correlation relations tested. We also find that one of the five correlation relations tested ($\epkk-E_\gamma$) has a significantly lower intrinsic dispersion compared to the other correlations. For this correlation relation, the maximum likelihood method favors the existence of a cosmological constant while the other four correlation favor a flat matter dominated universe $\omm \simeq 1$. Finally, a cross-correlation analysis between the GRBs and SnIa data for various values of $\omm$ has shown that the $E_{peak}-E_\gamma$ relation traces well the SnIa redshift regime. However, even the tightest correlation relation ($E_{peak}-E_\gamma$) provides much weaker constraints on $\omm$ than current SnIa data.

Short Gamma-Ray Bursts observed by PHEBUS

Statistical studies of Gamma-Ray Burst (GRB) properties have recently led to the discovery of a subclass within the population of classical events (Dezalayet al. 1992, Kouveliotouet al. 1993). Bursts belonging to this subclass are characterized by short durations, typically less than 2 seconds, and harder spectra on average. Using the PHEBUS GRB data set, we analyse the distributions of peak intensity, hardness ratio, and duration of the two subclasses. We also compare the sum spectra obtained with the brightest events to determine the ratio of total energies observed for each population.