Zsolt Bagoly

Gamma-ray bursts (GRBs) are bright transient sources that can be observed at high redshift. They can therefore be used as tracers of the distant large-scale structure, although the GRB redshift sample is sparse and affected by strong selection effects. We analyze the three-dimensional distribution of 542 GRBs with spectroscopic redshifts. The method extends our earlier spherical-window search by replacing spherical counting volumes with axisymmetric spheroids. The angular positions of the observed GRBs are kept fixed in the Monte-Carlo null samples, while the redshifts are shuffled within each Galactic hemisphere. In the Northern Galactic hemisphere, the overdensity associated with the Hercules–Corona Borealis Great Wall remains significant for a range of spheroidal shapes. This supports the stability of the previously reported signal and shows that it is not only a consequence of using spherical counting volumes. In the Southern Galactic hemisphere, the same method finds no structure with comparable significance. A small candidate grouping is present, but its significance is only marginal, and it is sensitive to the small number of events. We conclude that spheroidal resampling is a useful check of GRB overdensity searches, but the physical nature of any candidate structure still requires confirmation with independent tracers such as galaxy or quasar samples.

We analysed the spatial distribution of 542 GRBs with measured position and spectroscopic redshift up to 31 Aug 2022. Using kernel smoothing, we determined the GRB’s Sky Exposure Function and used it in the generation of random catalogues. The spatial Two-Point Correlation Function for GRBs was determined by partitioning the data based on the origin of the redshift (afterglow or host galaxy). The resulting ξ(r) Two-Point Correlation functions remain below the 3σ noise level, suggesting no significant differences between the Two-Point Correlation functions of the random and real datasets.

We analysed the different aspects of the spatial distribution of 542 Gamma-Ray Bursts with precisely determined positions and spectroscopic redshifts. The data were divided according to the origin of the redshift (afterglow or host galaxy). The yearly rate of afterglow and host-based redshift observations are different, with only a few host observations in the recent years. Since the launch of the Swift, the rate of afterglow observations fall exponentially by 50 % in 15 years, potentially affecting all planned GRB missions. We also analysed the rest-frame T90 values from the Swift BAT and FERMI GBM catalogues with the redshift data. The host- and afterglow-based points are separated in the redshift range due to observational effects, but no direct distinction could be made between the rest-frame T90 values. The correlation analysis between the GRB redshift and sky position shows that the GRB distribution could be factorised into a separate sky and radial components.

Gamma-ray bursts (GRBs) are the most luminous objects known: they outshine their host galaxies, making them ideal candidates for probing large-scale structure. Our aim is to determine the Spatial Two-Point Correlation Function of the GRBs with spectroscopic redshifts. We used all observations till 4 June 2021, and we also split the data according to the origin of the redshift (afterglow or host galaxy). We analyzed the possible correlation between the GRB redshift and sky position. There is only one region, called the Faraway GRB Patch, where nine distant GRBs shows deviation from the randomness with an ≈1% significance, showing that the sky and the radial component of the GRB distribution could be factorized and both can be determined independently. The GRBs’ cumulative monthly distribution was used to show that it is impossible to synthesize the Sky Exposure Function, even from the perfect observational logs. We estimated the Sky Exposure Function using the Gaussian kernel, and with the radial distribution, it was used for the estimation of the Spatial Two-Point Correlation Function. Monte Carlo simulations were used to determine the Poissonian errors. Our result shows that the current Spatial Two-Point Correlation Function estimations are consistent with zero for the full and the afterglow/host galaxy datasets.

Several hundred gamma-ray burst (GRB) redshifts have been determined to date. One of the other important properties—besides the distance—of the GRBs is the duration of the burst. In this paper, we analyse these two important quantities of the phenomena. In this paper, we map the two-dimensional distribution and explore some suspicious areas. As it is well known that the short GRBs are closer than the others, we search for parts in the Universe where the GRB duration is different from the others. We also analyse whether there are any ranges in the duration where the redshifts differ. We find some suspicious areas, however, no other significant region was found than the short GRB region.

The new, small satellite‐based gamma‐ray detectors, like Cubesats Applied for MEasuring and Localizing Transients, will provide a new way to detect gamma transients in the multimessenger era. The efficiency and the detection capabilities of such a system will be compared with current missions, for example, Fermi Gamma‐ray Burst Monitor (GBM). We used the Fermi GBM's observed short gamma‐ray burst light curves aggregated from observed discrete detector event for the simulation input. The corresponding direction‐dependent detector response matrices were used to generate photon counts and light curves around a simulated event, enabling to determine the statistics. This method can be used in the future for trigger algorithm and detector system development, and also to estimate the efficiency of the data analysis pipeline regarding the observable gamma‐ray bursts' parameters as well as other electromagnetic transients.