arXiv subjects

Ali M. Hasan

Publications and source records attributed to Ali M. Hasan.

3 recordsLinked to original sources

arXiv2026

Do the Amati and Yonetoku Relations Evolve with Redshift for Swift GRBs?

Gamma-ray bursts (GRBs) are extremely powerful stellar explosions that have been observed to huge distances with redshifts exceeding 9. Although GRBs are not standard candles, one may standardize them by calibrating certain correlations that link an intrinsic parameter to an observed one. Two such correlations that have been discovered are the Amati relation and the Yonetoku relation. In this paper, we compile a large sample of 241 Swift long GRBs for the purpose of examining whether the Amati and Yonetoku relations are immune to redshift evolution. Our methodology encompasses two approaches: the first involves binning the data by redshift and fitting the two relations for each bin, then checking whether the fitting parameters evolve with redshift; the second approach involves using a redshift cutoff to divide the data into a low-redshift group and a high-redshift group, then checking whether the fitting parameters for the two relations are consistent with one another. Our results indicate that the Amati and Yonetoku relations are robust in the sense that they do not show any systematic or significant redshift evolution. Moreover, our results indicate that the high redshift bins show better fits compared to the low redshift bins, which indicates that the Amati and Yonetoku relations are more reliable for high redshift and hence are promising cosmological probes.

astro-ph.HE↗

arXiv2025

Do Short GRBs Exhibit an Anticorrelation between Their Intrinsic Duration and Redshift?

Gamma-ray bursts (GRBs) are violent stellar explosions that are traditionally divided into two groups: short bursts (SGRBs) with an observed duration T90 < 2 s, and long bursts (LGRBs) with an observed duration T90 > 2 s, where T90 refers to the time needed for 90% of the fluence to be detected. Studies of progenitor models suggest that LGRBs emanate from the core collapse of massive stars, while SGRBs result from the merging of two compact objects, like two neutron stars or a neutron star and a black hole. Recent studies have found evidence that there is an anticorrelation between the intrinsic duration and the redshift of long GRBs. In this study, we first check whether LGRBs exhibit an anticorrelation between their intrinsic duration and redshift using an expanded dataset of long bursts that we have compiled. Next, we investigate whether this anticorrelation applies to SGRBs as well using a sample of short GRBs that we have compiled. Our analysis confirms the results obtained by previous studies regarding the anticorrelation for LGRBs. On the other hand, our results indicate that short GRBs do not exhibit such an anticorrelation. We discuss the implications of our results in the context of how metallicity evolves with redshift and the role that it might play in the aforementioned anticorrelation.

astro-ph.HE↗

arXiv2024

Does the Redshift Distribution of Swift Long GRBs Trace the Star-Formation Rate?

Gamma-ray bursts (GRBs) are extremely powerful explosions that have been traditionally classified into two categories: long bursts (LGRBs) with an observed duration T90 > 2 s, and short bursts (SGRBs) with an observed duration T90 < 2 s, where T90 is the time interval during which 90% of the fluence is detected. LGRBs are believed to emanate from the core-collapse of massive stars, while SGRBs are believed to result from the merging of two compact objects, like two neutron stars. Because LGRBs are produced by the violent death of massive stars, we expect that their redshift distribution should trace the star-formation rate (SFR). The purpose of our study is to investigate the extent to which the redshift distribution of LGRBs follows and reflects the SFR. We use a sample of 370 LGRBs taken from the Swift catalog, and we investigate different models for the LGRB redshift distribution. We also carry out Monte Carlo simulations to check the consistency of our results. Our results indicate that the SFR can describe the LGRB redshift distribution well for high redshift bursts, but it needs an evolution term to fit the distribution well at low redshift.

astro-ph.HE↗