Fermi Large Area Telescope observations of PSR J1836+5925

TL;DR

This paper reports on Fermi LAT observations of the gamma-ray pulsar PSR J1836+5925, providing detailed spectral, timing, and X-ray analysis, revealing its magnetospheric emission and neutron star characteristics.

Contribution

It offers the first comprehensive analysis of PSR J1836+5925's gamma-ray and X-ray properties, including timing, spectral data, and long-term behavior, highlighting its unique features among gamma-ray pulsars.

Findings

PSR J1836+5925 is a 173 ms pulsar with a characteristic age of 1.8 million years.

The pulsar exhibits large off-peak emission likely from magnetospheric processes.

X-ray observations show a spectrum consistent with a neutron star with magnetospheric and thermal emission.

Abstract

The discovery of the gamma-ray pulsar PSR J1836+5925, powering the formerly unidentified EGRET source 3EG J1835+5918, was one of the early accomplishments of the Fermi Large Area Telescope (LAT). Sitting 25 degrees off the Galactic plane, PSR J1836+5925 is a 173 ms pulsar with a characteristic age of 1.8 million years, a spindown luminosity of 1.1$\times10^{34}$ erg s$^{-1}$, and a large off-peak emission component, making it quite unusual among the known gamma-ray pulsar population. We present an analysis of one year of LAT data, including an updated timing solution, detailed spectral results and a long-term light curve showing no indication of variability. No evidence for a surrounding pulsar wind nebula is seen and the spectral characteristics of the off-peak emission indicate it is likely magnetospheric. Analysis of recent XMM observations of the X-ray counterpart yields a detailed characterization of its spectrum, which, like Geminga, is consistent with that of a neutron star showing evidence for both magnetospheric and thermal emission.