Studying the variability of the X‐ray spectral parameters of high‐redshift GRBs' afterglows

Rácz, I.; Hortobagyi, A. J.

doi:10.1002/asna.201813503

Cited by 3 publications

(3 citation statements)

References 40 publications

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“…In the spectral fitting we can use the redshift information, because the intrinsic hydrogen column density depends on the redshift (see in Section 2, Rácz & Hortobagyi (2018)). As where the redshifts were measured and the redshifts were used in calculating intrinsic hydrogen column density, it could have affected the result of the regression.…”

Section: Reliability Of Resultsmentioning

confidence: 99%

Estimating GRBs' cosmological distances

Racz

2023

caosp

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Several thousand gamma-ray bursts have been observed but more than 500 events have known distances. Numerous papers have shown huge structures in the Universe based on GRBs. We want to examine the distribution of the GRBs' distances, to give an estimation on the distances of those GRBs which have no measured redshifts. The GRB catalogs contain more than 100 physical parameters among which there can be parameters dependent on distance. In this work we examined the distances of Swift GRBs with machine learning methods. For the regression of the distances we used both Random Forest and XGBoost regression algorithms. We found an 0.76 strength correlation between the regressed and measured redshift.

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Section: Reliability Of Resultsmentioning

confidence: 99%

Estimating GRBs' cosmological distances

Racz

2023

caosp

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“…In addition to the H i data, we also analysed the FIR data for fluctuations. We Fourier transformed the Planck N(H) maps with routines written in IDL based on the standard IDL FFT routine with periodogram normalization (Press et al 1992). For all maps the highest spatial sampling frequency corresponds to the pixel size of the used Planck images (225 × 225).…”

Section: Fluctuations In the Planck Datamentioning

confidence: 99%

“…For all maps the highest spatial sampling frequency corresponds to the pixel size of the used Planck images (225 × 225). The Nyquist limit that allows correct sampling (without aliasing) is half of that frequency (Press et al 1992, Chap. 12.1), i.e.…”

Section: Fluctuations In the Planck Datamentioning

confidence: 99%

Exploring the pattern of the Galactic HI foreground of GRBs with the ATCA

Dénes

Jones

Tóth

et al. 2019

Monthly Notices of the Royal Astronomical Society

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The afterglow of a gamma ray burst (GRB) can give us valuable insight into the properties of its host galaxy. To correctly interpret the spectra of the afterglow we need to have a good understanding of the foreground interstellar medium (ISM) in our own Galaxy. The common practice to correct for the foreground is to use neutral hydrogen (H i) data from the Leiden/Argentina/Bonn (LAB) survey. However, the poor spatial resolution of the single dish data may have a significant effect on the derived column densities. To investigate this, we present new high-resolution H i observations with the Australia Telescope Compact Array (ATCA) towards 4 GRBs. We combine the interferometric ATCA data with single dish data from the Galactic All Sky Survey (GASS) and derive new Galactic H i column densities towards the GRBs. We use these new foreground column densities to fit the Swift XRT X-ray spectra and calculate new intrinsic hydrogen column density values for the GRB host galaxies. We find that the new ATCA data shows higher Galactic H i column densities compared to the previous single dish data, which results in lower intrinsic column densities for the hosts. We investigate the line of sight optical depth near the GRBs and find that it may not be negligible towards one of the GRBs, which indicates that the intrinsic hydrogen column density of its host galaxy may be even lower. In addition, we compare our results to column densities derived from far-infrared data and find a reasonable agreement with the H i data.

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Some statistical remarks on GRBs jointly detected by Fermi and Swift satellites

Pinter,

Balazs,

Bagoly

et al. 2023

Monthly Notices of the Royal Astronomical Society

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We made statistical analysis of the Fermi GBM and Swift BAT observational material, accumulated over 15 yr. We studied how GRB parameters (T90 duration, fluence, and peak flux) that were observed by only one satellite differ from those observed by both. In the latter case, it was possible to directly compare the values of the parameters that both satellites measured. The GRBs measured by both satellites were identified using the k-nearest neighbours algorithm in Euclidean distance. In the parameter space we determined the direction in which the jointly detected GRBs differ most from those detected by only one of the instruments using linear discriminant analyses. To get the strength of the relationship between the parameters obtained from the GBM and BAT, a canonical correlation was performed. The GBM and BAT T90 distributions were fitted with a linear combination of lognormal functions. The optimal number of such functions required for fit is two for GBM and three for BAT. Contrary to the widely accepted view, we found that the number of lognormal functions required for fitting the observed distribution of GRB durations does not allow us to deduce the number of central engine types responsible for GRBs.

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Studying the variability of the X‐ray spectral parameters of high‐redshift GRBs' afterglows

Cited by 3 publications

References 40 publications

Estimating GRBs' cosmological distances

Estimating GRBs' cosmological distances

Exploring the pattern of the Galactic HI foreground of GRBs with the ATCA

Some statistical remarks on GRBs jointly detected by Fermi and Swift satellites

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