Gaussian-mixture-model-based cluster analysis of gamma-ray bursts in the BATSE catalog

Abstract

Clustering is an important tool to describe gamma-ray bursts (GRBs). We analyzed the Final BATSE Catalog using Gaussian-mixture-models-based clustering methods for six variables (durations, peak flux, total fluence and spectral hardness ratios) that contain information on clustering. Our analysis found that the five kinds of GRBs previously found by other authors are only the cut groups of the previously well-known three types (short, long and intermediate in duration). The two short and intermediate duration groups differ mostly in the peak flux. Therefore, the reanalysis of the BATSE data finds similar group structures than previously. Because the brightness distribution is asymmetric and not correlated with durations or hardnesses the Gaussian mixture model cuts the Short and the Intermediate duration groups into two subgroups, the dim ones and the bright ones.

Multivariate Analysis of BATSE Gamma-Ray Burst Properties Using Skewed Distributions

“…spanned by the PCs, up to a four-dimensional log T 90 − log F tot − log H 32 − log P 256 instance (see Table 1). The six-dimensional case (Mukherjee et al 1998;Chattopadhyay & Maitra 2017;Tóth et al 2019), i.e. with added T 50 and H 321 , was not taken into account due to very high correlations (r > 0.96) between T 90 and T 50 , and between H 32 and H 321 .…”

“…Most recently, Tóth et al (2019) performed the usual Gaussian mixture modeling of the BATSE catalog, utilizing six variables 4 : T 90 , T 50 , F tot , P 256 , H 32 , and H 321 . They found that this six-dimensional space is best described by five Gaussian components, consistent with (Chattopadhyay & Maitra 2017).…”

Graph-based clustering of gamma-ray bursts

“…Moreover, considering skewed distributions, two-component mixtures have also been indicated (Tarnopolski 2019b,a). In higher-dimensional spaces, things become less unambiguous (Mukherjee et al 1998;Chattopadhyay et al 2007;Chattopadhyay & Maitra 2017Modak et al 2018;Acuner & Ryde 2018;Horváth et al 2019;Tóth et al 2019;Tarnopolski 2019c). For the most recent, detailed overview on the topic of parametric clustering of GRBs, readers can refer to Tarnopolski (2019c).…”

How does the shape of gamma-ray bursts' pulses affect the duration distribution?

“…This generally holds in higherdimensional parameter spaces as well (Tarnopolski 2019b,a,c). It was sometimes noted that the distributions appear skewed, though (e.g., Mukherjee et al 1998;Tóth et al 2019), but such observation was not followed by employing asymmetric models.…”