Gazing at the ultra-slow magnetar in RCW 103 with NuSTAR and Swift

TL;DR

This study presents NuSTAR and Swift observations of the peculiar magnetar candidate 1E 161348-5055 in RCW 103, revealing its spectral properties, flux evolution, and confirming its status as the slowest magnetar known.

Contribution

The paper provides the first detailed spectral and timing analysis of 1E 161348-5055 confirming its classification as a magnetar with an unprecedented slow rotation period.

Findings

Spectral fits suggest blackbody or blackbody plus power law models.

Flux decreased by a factor of three since outburst onset.

Detected a 6.67-hour periodic modulation.

Abstract

We report on a new NuSTAR observation and on the ongoing Swift XRT monitoring campaign of the peculiar source 1E 161348-5055, located at the centre of the supernova remnant RCW 103, which is recovering from its last outburst in June 2016. The X-ray spectrum at the epoch of the NuSTAR observation can be described by either two absorbed blackbodies ($kT_{BB_1}$ ~ 0.5 keV, $kT_{BB_2}$ ~ 1.2 keV) or an absorbed blackbody plus a power law ($kT_{BB_1}$ ~ 0.6 keV, $\Gamma$ ~ 3.9). The observed flux was ~ 9 $\times$ 10$^{-12}$ erg s$^{-1}$ cm$^{-2}$, ~ 3 times lower than what observed at the outburst onset, but about one order of magnitude higher than the historical quiescent level. A periodic modulation was detected at the known 6.67 hr periodicity. The spectral decomposition and evolution along the outburst decay are consistent with 1E 161348-5055 being a magnetar, the slowest ever detected.