arXiv subjects

Keneth Garcia-Cifuentes

Publications and source records attributed to Keneth Garcia-Cifuentes.

3 recordsLinked to original sources

arXiv2024

ClassiPyGRB: Machine Learning-Based Classification and Visualization of Gamma Ray Bursts using t-SNE

Gamma-ray burst (GRBs) are the brightest events in the universe. For decades, astrophysicists have known about their cosmological nature. Every year, space missions such as Fermi and SWIFT detect hundreds of them. In spite of this large sample, GRBs show a complex taxonomy in the first seconds after their appearance, which makes it very difficult to find similarities between them using conventional techniques. It is known that GRBs originate from the death of a massive star or from the merger of two compact objects. GRB classification is typically based on the duration of the burst (Kouveliotou et al., 1993). Nevertheless, events such as GRB 211211A (Yang et al., 2022), whose duration of about 50 seconds lies in the group of long GRBs, has challenged this categorization by the evidence of features related with the short GRB population (the kilonova emission and the properties of its host galaxy). Therefore, a classification based only on their gamma-ray duration does not provide a completely reliable determination of the progenitor. Motivated by this problem, Jespersen et al. (2020) and Steinhardt et al. (2023) carried out analysis of GRB light curves by using the t-SNE algorithm, showing that Swift/BAT GRBs database, consisting of light curves in four energy bands (15-25 keV, 25-50 keV, 50-100 keV, 100-350 keV), clusters into two groups corresponding with the typical long/short classification. However, in this case, this classification is based on the information provided by their gamma-ray emission light curves. ClassiPyGRB is a Python 3 package to download, process, visualize and classify GRBs database from the Swift/BAT Instrument (up to July 2022). It is distributed over the GNU General Public License Version 2 (1991). We also included a noise-reduction and an interpolation tools for achieving a deeper analysis of the data.

astro-ph.HE↗

arXiv2023

Machine-Learning Enhanced Photometric Analysis of the Extremely Bright GRB 210822A

We present analytical and numerical models of the bright long GRB 210822A at $z=1.736$. The intrinsic extreme brightness exhibited in the optical, which is very similar to other bright GRBs (e.g., GRBs 080319B, 130427A, 160625A 190114C, and 221009A), makes GRB 210822A an ideal case for studying the evolution of this particular kind of GRB. We use optical data from the RATIR instrument starting at $T+315.9$ s, with publicly available optical data from other ground-based observatories, as well as Swift/UVOT, and X-ray data from the Swift/XRT instrument. The temporal profiles and spectral properties during the late stages align consistently with the conventional forward shock model, complemented by a reverse shock element that dominates optical emissions during the initial phases ($T<300$ s). Furthermore, we observe a break at $T=80000$s that we interpreted as evidence of a jet break, which constrains the opening angle to be about $θ_\mathrm{j}=(3-5)$ degrees. Finally, we apply a machine-learning technique to model the multi-wavelength light curve of GRB 210822A using the AFTERGLOWPY library. We estimate the angle of sight $θ_{obs}=(6.4 \pm 0.1) \times 10^{-1}$ degrees, the energy $E_0=(7.9 \pm 1.6)\times 10^{53}$ ergs, the electron index $p=2.54 \pm 0.10$, the thermal energy fraction in electrons $ε_\mathrm{e}=(4.63 \pm 0.91) \times 10^{-5}$ and in the magnetic field $ε_\mathrm{B}= (8.66 \pm 1.01) \times 10^{-6}$, the efficiency $χ= 0.89 \pm 0.01$, and the density of the surrounding medium $n_\mathrm{0} = 0.85 \pm 0.01 cm^{-3}$.

astro-ph.HE↗

arXiv2023

Unraveling Parameter Degeneracy in GRB Data Analysis

Gamma-ray burst (GRB) afterglow light curves and spectra provide information about the density of the environment, the energy of the explosion, the properties of the particle acceleration process, and the structure of the decelerating jet. Due to the large number of parameters involved, the model can present a certain degree of parameter degeneracy. In this paper, we generated synthetic photometric data points using a standard GRB afterglow model and fit them using the Markov Chain Monte Carlo (MCMC) method. This method has emerged as the preferred approach for analysing and interpreting data in astronomy. We show that, depending on the choice of priors, the parameter degeneracy can go unnoticed by the MCMC method. Furthermore, we apply the MCMC method to analyse the GRB~170817A afterglow. We find that there is a complete degeneracy between the energy of the explosion $E$, the density of the environment $n$, and the microphysical parameters describing the particle acceleration process (e.g. $ε_e$ and $ε_B$), which cannot be determined by the afterglow light curve alone. Our results emphasise the importance of gaining a deep understanding of the degeneracy properties which can be present in GRB afterglows models, as well as the limitations of the MCMC method. In the case of GRB 170817, we get the following values for the physical parameters: $E=8\times 10^{50}-1 \times 10^{53}$ erg, $n=7\times 10^{-5}-9\times10^{-3}$, $ε_e=10^{-3}-0.3$, $ε_B=10^{-10}-0.3$.

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