Post-outburst Observations of the Magnetically Active Pulsar J1846-0258: a new braking index, increased timing noise, and radiative recovery

TL;DR

This study reports post-outburst observations of pulsar J1846-0258, revealing a decreased braking index, increased timing noise, and stable X-ray flux, shedding light on its magnetar-like behavior and recovery process.

Contribution

It provides the first detailed measurement of the pulsar's braking index after a magnetar-like outburst, highlighting changes in spin-down behavior and timing noise.

Findings

Braking index decreased from 2.65 to 2.16 after outburst.

Timing noise increased significantly post-outburst.

X-ray flux and spectrum remained consistent with pre-outburst levels.

Abstract

The ~800 yr-old pulsar J1846-0258 is a unique transition object between rotation-powered pulsars and magnetars: though behaving like a rotation-powered pulsar most of the time, in 2006 it exhibited a distinctly magnetar-like outburst accompanied by a large glitch. Here we present X-ray timing observations taken with the Rossi X-ray Timing Explorer over a 2.2-yr period after the X-ray outburst and glitch had recovered. We observe that the braking index of the pulsar, previously measured to be n=2.65+/-0.01, is now n=2.16+/-0.13, a decrease of 18+/-5%. We also note a persistent increase in the timing noise relative to the pre-outburst level. Despite the timing changes, a 2009 Chandra X-ray Observatory observation shows that the X-ray flux and spectrum of the pulsar and its wind nebula are consistent with the quiescent levels observed in 2000.