arXiv subjects

Youngwan Son

Publications and source records attributed to Youngwan Son.

3 recordsLinked to original sources

arXiv2026

Enhancing event reconstruction for $γ$-ray particle detector arrays using transformers

Gamma-ray astronomy from hundreds of GeV to PeV is confined to ground-based experiments that detect air showers induced by $γ$-rays entering Earth's atmosphere. While particle detector arrays feature huge detection areas, accurately reconstructing the primary particle properties is difficult due to the sparse sampling of the air shower and its intrinsic fluctuations. In this work, using simulations of a future water-Cherenkov array, we investigate two end-to-end deep learning approaches based on the transformer architecture with different computational complexities that utilize calibrated raw data. We benchmark both methods against well-established methods in the field in terms of $γ$-hadron separation, angular, core, and energy reconstruction. Our results show significant improvements across the whole energy range, particularly at low and intermediate energies. This work is the first to consistently demonstrate improved performance in both event reconstruction and $γ$-hadron separation using a single architecture.

astro-ph.IM↗

arXiv2026

An 18-year Fermi-LAT stacking limit on GeV $γ$-ray emission from particle-accelerating colliding-wind binaries

The wind-collision regions of massive colliding-wind binaries (CWBs) accelerate relativistic particles, as shown by their non-thermal radio synchrotron and, in $η$ Car, hard X-ray emission. Whether CWBs emit GeV $γ$rays as a population is unknown: only $η$ Car is unambiguously detected by the Fermi Large Area Telescope (LAT). We analyze 17.8 yr of Fermi-LAT data above 1 GeV (where the sharp point-spread function controls plane confusion) at the 61 confirmed (list A) particle-accelerating CWBs (PACWBs) of De Becker & Raucq, using a two-dimensional (photon index $\times$ flux) likelihood scan against 200 control fields matched in latitude, local source density, and diffuse intensity. Removing systems whose lines of sight coincide with bright catalogue $γ$-ray sources leaves a clean, mutually isolated sample of 6, whose stack is consistent with the control-field null ($p=0.83$): no evidence for collective GeV emission. Retaining those systems instead yields a spurious $\gtrsim3.5σ$ excess from chance catalogue coincidences, a caveat for Galactic-plane stacking. The resulting 95% limit on the mean per-source flux, $F(>1\,\mathrm{GeV})\lesssim1.1\times10^{-11}~\mathrm{ph\,cm^{-2}\,s^{-1}} (Γ=2)$, implies a $γ$-ray production efficiency $η=L_γ/L_{\rm wind}\lesssim4\times10^{-6}\,(d/\mathrm{kpc})^2$, about two orders of magnitude below $η$ Car at the sample's median distance. A representative single-zone model then bounds the electron acceleration efficiency in CWB wind-collision regions unless their magnetic field is comparable to or above the magnetic-photon equipartition value. Among the high-latitude systems accessible to a clean stack, $η$ Car thus appears to be a singular object rather than the brightest member of an emerging population.

astro-ph.HE↗

arXiv2021

Studying High-Mass Microquasars with HAWC

High-mass microquasars (HMMQs) are powerful particle accelerators, but their mechanism of the high-energy emission is poorly understood. To date, only a handful of these particle engines have ever been observed to emit gamma-ray photons and are thus potential TeV gamma-ray emitters. In this work, we study four HMMQs, namely, LS 5039, Cyg X-1, Cyg X-3, and SS 433 using the data from the High Altitude Water Cherenkov (HAWC) observatory. We perform time dependent analyses on each HMMQ to look for any periodic variations in their flux. We produce light curves using the HAWC daily maps from which we generate Lomb-Scargle periodograms. By analysing the significance of the periodogram peaks, we assess whether or not HAWC is sensitive to orbitally modulating TeV gamma-ray flux in the four HMMQs.

astro-ph.HE↗