The Variable Pulsar Wind Nebula of PSR J1809-1917

TL;DR

This study presents detailed X-ray observations of the pulsar PSR J1809-1917 and its variable pulsar wind nebula, revealing morphological features, jet structures, and spectral properties that support their association with a TeV gamma-ray source.

Contribution

First detailed X-ray analysis of PSR J1809-1917's variable PWN, including jet detection and morphological variability, linking it to TeV gamma-ray emission.

Findings

PWN consists of a compact nebula and extended emission up to 2' from the pulsar.

Detected small-scale jets with a hard spectrum aligned with the nebula.

Observed morphological and flux variability in the compact nebula over months.

Abstract

PSR J1809-1917 is a young ($\tau=51$ kyr) energetic ($\dot{E}=1.8\times10^{36}$ erg s$^{-1}$) radio pulsar powering a pulsar wind nebula (PWN). We report on the results of three Chandra X-ray Observatory observations which show that the PWN consists of a small ($\sim 20''$) bright compact nebula (CN) and faint extended emission seen up to $2'$ from the pulsar. The CN is elongated in the northeast-southwest direction and exhibits morphological and flux variability on a timescale of a few months. We also find evidence of small arcsecond-scale jets extending from the pulsar along the same direction, and exhibiting a hard power-law (PL) spectrum with photon index $\Gamma_{\rm jet}=1.2\pm0.1$. The more extended emission and CN share the same symmetry axis, which is also aligned with the direction toward the TeV $\gamma$-ray source HESS J1809--193, supporting their association. The spectrum of the extended nebula (EN) fits an absorbed PL with about the same slope as that of the CN, $\Gamma_{\rm CN}\approx\Gamma_{\rm EN}=1.55\pm0.09$; no spectral changes across the EN's 2 pc extent are seen. The total PWN 0.5-8 keV luminosity is $L_{\rm PWN}\approx 9\times10^{32}$ erg s$^{-1}$, about half of which is due to the EN.