GeV gamma-ray emission in the field of the shell-type supernova remnant Vela Jr revisited

TL;DR

This study revisits GeV gamma-ray emission from supernova remnant Vela Jr using 15 years of Fermi-LAT data, modeling its morphology and spectrum, and explores multi-wavelength emission with leptonic and hybrid models.

Contribution

It provides an improved, detailed morphological and spectral analysis of Vela Jr's GeV emission and supports a mixed leptonic-hadronic origin for the broadband emission.

Findings

The GeV morphology aligns with the H.E.S.S. shell template.

The GeV spectrum is a hard power law with photon index 1.77.

Hybrid lepton-hadron models better fit the multi-wavelength data.

Abstract

We present an updated analysis of the gigaelectronvolt (GeV) gamma-ray emission from the shell-type supernova remnant (SNR) RX J0852.0-4622 (Vela Jr) using 15 yr of Fermi Large Area Telescope (Fermi-LAT) data. We quantitatively model the GeV morphology and find that it is best described by the masked H.E.S.S. shell template, indicating that the embedded pulsar wind nebula (PWN) contributes little to the GeV flux. The 0.1-500 GeV spectrum is well fitted by a hard power law with a photon index of $1.77 \pm 0.03$ and connects smoothly to the teraelectronvolt (TeV) spectrum, confirming previous results with improved precision. We further construct an independent eROSITA shell template and derive the 1-5 keV X-ray spectral energy distribution (SED) of the whole remnant, which provides new constraints on the synchrotron emission. We model the multi-wavelength (MWL) SED with a pure leptonic model and a hybrid lepton-hadron model. While the pure leptonic model reproduces the overall broadband shape, the hybrid model provides a better statistical description of the same dataset, supporting a mixed-origin picture in which the hadronic contribution is mainly relevant in the GeV band and the TeV emission remains predominantly leptonic.