Searcharxiv⌕ Search

arXiv subjects

Emre S. Yorgancioglu

Publications and source records attributed to Emre S. Yorgancioglu.

4 recordsLinked to original sources
arXiv2026

Relativistic \(^{56}\text{Ni}\) Decay Lines in GRB 221009A

Long Gamma Ray Bursts are thought to originate from the core collapse of massive stars that give rise to energetic broad-lined Type Ic supernovae. The brightest burst ever recorded, GRB 221009A, has been linked to a broad-lined Type Ic supernova through late-time observations by the James Webb Space Telescope. An emission line evolving from $\sim$37 to $\sim$6~MeV is detected during the prompt phase. We propose that this time-evolving line is consistent with Doppler-boosted radioactive decay of nickel synthesized in the associated supernova and entrained in the relativistic jet, corresponding to the boosted 158~keV decay branch. We also report evidence for an additional higher-energy excess near $\sim$24~MeV at 290--300~s, detected at moderate statistical significance and consistent with the boosted 270~keV decay branch. The observed kinematics and flux evolution are compatible with expectations from radioactive decay, providing direct spectroscopic evidence linking prompt emission to supernova nucleosynthesis.

astro-ph.HE↗
arXiv2025

Can GRB Empirical Correlations Be Used for Population Studies?

Only a small fraction of Gamma-ray bursts (GRBs) have independent redshift measurements, which are essential for understanding their intrinsic properties. For this reason, empirical correlations of GRBs have often been touted as useful distance indicators, for both individual GRBs as well as population studies. Building upon our previous work, we test the ability of the Yonetoku, 3D Dainotti, and the L-T-E correlation to adequately constrain the GRB rate, $Ψ_{GRB}$. Our analysis demonstrates that, even under idealized conditions that neglect substantial uncertainties, the derived redshift solutions cannot accurately constrain $Ψ_{GRB}$, regardless of the intrinsic distribution's characteristic width. We thus demonstrate unequivocally that -- notwithstanding the questionable assumption of no selection biases -- empirical GRB correlations alone cannot serve as reliable distance indicators at either the individual or population level.

astro-ph.HE↗
arXiv2025

Investigating the Dainotti Relation in Gamma-Ray Bursts through Multipolar Electromagnetic Radiation

The Dainotti relation empirically connects the isotropic plateau luminosity ($L_X$) in gamma-ray bursts (GRBs) X-ray afterglows to the rest-frame time at which the plateau ends ($T_a^*$), enabling both the standardization of GRBs and their use as cosmological probes. However, the precise physical mechanisms underlying this correlation remain an active area of research. Although magnetars, highly magnetized neutron stars, have been proposed as central engines powering GRB afterglows, traditional dipole spin-down radiation models fail to account for the full diversity of observed behaviors. This limitation necessitates a more comprehensive framework. We propose that multipolar magnetic field emissions from magnetars offer a plausible explanation for the Dainotti relation. Unlike simple dipole fields, higher-order multipolar configurations enable more complex energy dissipation processes. The coexistence of multiple components can plausibly explain the range of afterglow decay indices found from a sample of 238 GRBs with plateau features from the Swift-XRT database up to the end of December 2024, the majority of which deviate from the dipolar prediction of $α= -2$, and more crucially, the spin-down physics yields a link between $L_X$ and $T_a^*$ in a way that preserves the Dainotti correlation with a slope of $b = - 1$, independent of the specific multipole order. Moreover, we find that the inclusion of higher order multipoles can explain the range of plateau energies found in the Dainotti relations. Thus, a unified picture emerges in which multipolar fields are able to reproduce both the slope and the normalization of the correlation.

astro-ph.HE↗
arXiv2025

On the Feasibility of Deriving Pseudo-Redshifts of Gamma-ray Bursts from Two Phenomenological Correlations

Accurate knowledge of gamma-ray burst (GRB) redshifts is essential for studying their intrinsic properties and exploring their potential application in cosmology. Currently, only a small fraction of GRBs have independent redshift measurements, primarily due to the need of rapid follow-up optical/IR spectroscopic observations. For this reason, many have utilized phenomenological correlations to derive pseudo-redshifts of GRBs with no redshift measurement. In this work, we explore the feasibility of analytically deriving pseudo-redshifts directly from the Amati and Yonetoku relations. We simulate populations of GRBs that (i) fall perfectly on the phenomenological correlation track, and (ii) include intrinsic scatter matching observations. Our findings indicate that, in the case of the Amati relation , the mathematical formulation is ill-behaved so that it yields two solutions within a reasonable redshift range $z \in [0.1, 10] $. When realistic scatter is included, it may result in no solution, or the redshift error range is excessively large. In the case of the Yonetoku relation, while it can result in a unique solution in most cases, the large systematic errors of the redshift calls for attention, especially when attempting to use pseudo redshifts to study GRB population properties.

astro-ph.HE↗