The Vela pulsar and its pulsar wind nebula Vela-X using 13 years of Fermi-LAT Observations

TL;DR

This study analyzes 13 years of Fermi-LAT data to characterize the Vela pulsar and its nebula Vela-X, revealing their spectral properties, spatial components, and phase-resolved spectra across multiple energy bands.

Contribution

It provides a detailed, multi-component model of Vela-X and phase-resolved spectral analysis of the Vela pulsar based on extensive gamma-ray observations.

Findings

Vela-X is best modeled with two extended components: a large Gaussian and a compact disk.

The spectral index for both components is approximately 2.3, supporting a common PWN origin.

Phase-resolved analysis reveals detailed spectral properties, including peak energy and spectral indices, across different pulse phases.

Abstract

We present results of more than 13 years of Fermi-LAT data analysis for the Vela pulsar from 60 MeV to 100 GeV and its pulsar wind nebula (PWN), Vela-X, for E > 1 GeV in the off-pulse phases. We find the Vela-X PWN can be best characterized using two extended components: a large radial Gaussian accompanied by an off-set, compact radial disk, both with a similar spectral index, \Gamma \sim 2.3. The common spectral properties support a common PWN origin, but a supernova remnant component is plausible for the compact radial disk. With an updated Vela-X model, the phase resolved spectral properties of the Vela pulsar are explored through a phase-resolved analysis. The phase-resolved spectral properties of the pulsar are presented, such as the SED peak energy E$_p$, the width of the SED at its peak, d$_p$, and the asymptotic (low-energy) spectral index, $\Gamma_0$, are presented. The best-fit spectral models for each LAT pulse peak (Peak 1 and Peak 2) are extrapolated to UV energies and compared to archival, phase-resolved spectra at UV, X-ray, soft \gamma-ray and TeV energies. We also discuss the physical implications of our modeling and the data comparisons.