arXiv subjects

Ekrem Oğuzhan Angüner

Publications and source records attributed to Ekrem Oğuzhan Angüner.

3 recordsLinked to original sources

arXiv2026

The GPSP Atlas: High-resolution Galactic Photon Survival Probability Atlas for Very-High- and Ultra-High-Energy Gamma-Ray Astronomy

The emergence of Galactic PeV astronomy makes photon--photon ($γγ$) absorption an increasingly important component of gamma-ray data analysis. In this work, the Galactic Photon Survival Probability (GPSP) atlas is presented as the first Galactic framework describing gamma-ray survival probabilities over the full parameter space $P(l,b,d,E_γ)$ between 1 TeV and 10 PeV. The atlas is constructed using two independent GALPROP-based interstellar radiation field (ISRF) models, allowing direct assessment of ISRF-related systematics, and is released in a FITS format compatible with standard analysis frameworks. A novel gamma-ray survival phase space representation is introduced, extending 1D survival profiles into a 2D energy--distance framework that visualizes Galactic transparency and gamma-ray horizons. Using the full atlas, Galactic transparency and Galactic plane survival maps are constructed. These reveal that Galactic opacity is highly structured, with enhanced attenuation along spiral-arm tangent directions in the $\sim$100--300 TeV regime, while attenuation becomes nearly isotropic and cosmic microwave background (CMB) dominated near PeV energies. The framework naturally accommodates attenuation calculations for extended and diffuse sources. The atlas is further extended to subluminal Lorentz invariance violation (LIV) scenarios through the GPSP-LIV atlas, incorporating LIV-modified pair production kinematics and cross sections. Sources emitting in the 2--3 PeV regime beyond gamma-ray horizons are identified as promising targets for probing LIV effects. Finally, practical applications are presented for the Galactic Center PeVatron and the Cygnus X-3 regions. The GPSP and GPSP-LIV atlases establish a publicly available foundation for studies of Galactic PeVatrons, diffuse gamma-ray emission, and fundamental physics searches in the emerging era of Galactic PeV astronomy.

astro-ph.HE↗

arXiv2025

Prediction of radio-quiet gamma-ray pulsar distances using the Fundamental Plane relation

The fundamental plane (FP) relation connects gamma-ray luminosity to intrinsic pulsar properties, offering the potential to estimate distances for radio-quiet (RQ) gamma-ray pulsars, where direct measurements are often unavailable. The Fermi Third Pulsar Catalog presents spectral data for 294 gamma-ray pulsars, including 72 RQ pulsars, of which only 9 have known distances. This study investigates the FP relation's potential to predict distances for RQ gamma-ray pulsars using machine learning (ML) approaches. Ordinary least-squares regression was employed alongside ML methods, including random forest and support vector regression, to predict RQ gamma-ray pulsar distances. To ensure robustness, the analysis considered spectral cutoff significance and outlier data. Results confirm that the FP relation is valid only for pulsars exhibiting significant gamma-ray cutoffs, with FP exponents closely matching theoretical expectations. It was shown that gamma-ray emission origins significantly favor the curvature radiation regime over the synchrotron regime at the 4.2 sigma level. The distances for 62 RQ pulsars, for which no traditional measurements exist, are predicted for the first time. The luminosity and spatial distributions of the considered RQ pulsar population match known pulsar distributions. Predictions for RQ pulsars with known distances are consistent with measured data. This study provides a proof of principle that the FP relation, combined with ML methods, is a promising tool for distance estimation in RQ gamma-ray pulsars, using gamma-ray emission directly for the first time in pulsar distance estimates. Future improvements can be achieved with larger data sets, precise spectral cutoff determinations, and corrections for key factors like the beaming factor.

astro-ph.HE↗

arXiv2024

The expected potential of hadronic PeVatron searches with spectral $γ$-ray data from the Southern Wide-field Gamma-ray Observatory

The presence of a spectral softening, occurring at 3 PeV energies, seen in the local cosmic-ray energy spectrum provides an evidence that our Galaxy hosts astrophysical objects, known as hadronic PeVatrons, that are capable of accelerating hadrons to PeV energies and above. Recent results from ground-based particle detector array experiments have provided conclusive evidence that these facilities are essential to explore the ultra-high-energy (UHE, E>100 TeV) domain and pinpoint the location of PeVatrons in the Galaxy. The Southern Wide-field Gamma-ray Observatory (SWGO) is proposed next-generation ground-based extensive air shower observatory, which holds great scientific potential for UHE observations. In this study, we investigate the expected potential of SWGO to search for hadronic PeVatrons, based on the publicly available preliminary SWGO straw-man IRFs. It can be shown that the SWGO detection of gamma-ray spectral cutoffs between 30 TeV and 100 TeV is possible for faint gamma-ray sources of 5~mCrab given that the spectral index is hard ($Γ$<2.0), while spectral cutoffs from softer sources with $Γ$=2.3 can be detected for sources brighter than 11-12 mCrab. The reconstructed SWGO PeVatron detection maps demonstrate that the future SWGO experiment can probe large parts of the investigated PeVatron parameter space, providing a robust detection and/or rejection of presence of spectral signatures associated with hadronic PeVatrons. A dedicated study on the promising PeVatron candidates, the Galactic Center region, Westerlund~1, HESSJ1702-420 and HESSJ1641-463, shows that the SWGO will have a great potential to confirm or exclude PeVatron nature of these candidate sources at a robust significance level after 5-years of observation. In addition, it is shown that controlling systematic errors will be necessary to reach full potential of the SWGO experiment for PeVatron searches.

astro-ph.HE↗