On the Investigation of the Closure Relations for Gamma-Ray Bursts Observed by Swift in the Post-plateau Phase and the GRB Fundamental Plane

We have developed a functional fit which can be used to represent the entire temporal decay of the X-ray afterglow of gamma-ray bursts (GRBs). The fit delineates and parameterizes well-defined phases for the decay: the prompt emission; an initial steep decay; a shallow plateau phase; and finally, a powerlaw afterglow. For 20% of GRBs, the plateau phase is weak, or not seen, and the initial powerlaw decay becomes the final afterglow. We compare the temporal decay parameters and X-ray spectral indices for 107 GRBs discovered by Swift with the expectations of the standard fireball model including a search for possible jet breaks. For approximately 50% of GRBs, the observed afterglow is in accord with the model, but for the rest the temporal and spectral properties are not as expected. We identify a few possible jet breaks, but there are many examples where such breaks are predicted but are absent. We also find that the start time of the final afterglow decay, T a , is associated with the peak of the prompt γ -ray emission spectrum, E peak , just as optical jet-break times, t j , are associated with E peak in the Ghirlanda relation.

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Gamma-ray Bursts Cosmology with The X-ray Fundamental Plane Relation

10.21203/rs.3.rs-108982/v1 ◽

2020 ◽

Author(s):

Maria Dainotti ◽

Jacob Fernandez ◽

Giuseppe Saraccino ◽

Aleksander Lenart ◽

Sergey Postnikov ◽

...

Keyword(s):

Gamma Ray ◽

Background Radiation ◽

Cosmological Parameters ◽

Energy Parameter ◽

Hubble Constant ◽

Matter Content ◽

Gamma Ray Bursts ◽

Opening Angle ◽

Fundamental Plane ◽

X Ray

Abstract Cosmological models and the value of their parameters are at the center of the debate because of the tension between the results obtained by the SNe Ia data and the Plank ones of the Cosmic Microwave Background Radiation. Thus, adding cosmological probes observed at high redshifts, such as Gamma-Ray Bursts (GRBs), is needed. Using GRB correlations between luminosities and a cosmological independent variable is challenging because GRB luminosities vary widely. We corrected a tight correlation between the rest-frame end time of the X-ray plateau, its corresponding X-ray luminosity, and the peak prompt luminosity: the so-called fundamental plane relation, using the jet opening angle. Its intrinsic scatter is 0:017 m 0:010 dex, 95% smaller than the isotropic fundamental plane relation, the smallest compared to any current GRB correlation in the literature. This shows that GRBs can be used as reliable cosmological tools. We use this GRB corrected correlation for the so-called platinum sample (a well-defined set with relatively flat plateaus), together with SNe Ia data, to constrain different cosmological parameters like the matter content of the universe today, M, the Hubble constant H0, and the dark energy parameter w for a wCDM model. We confirm the wCDM model but using GRBs up to z = 5, a redshift range much larger than one of SNe Ia.

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