Swift monitoring of the central X-ray source in RCW 103

TL;DR

This paper reports on five years of Swift X-ray observations of the enigmatic source 1E 161348-5055 in RCW 103, providing precise period measurement and constraints on its period derivative, revealing its quiescent state and long-term behavior.

Contribution

The study offers the first accurate period measurement and upper limit on period derivative for 1E 161348-5055, enhancing understanding of its nature and variability.

Findings

Source remained in quiescence over five years.

Measured period of approximately 24,030 seconds.

Established an upper limit on period derivative.

Abstract

The X-ray source 1E 161348-5055 lies at the centre of the 2-kyr-old supernova remnant RCW 103. Owing to its 24-ks modulation, orders-of-magnitude flux variability over a few months/years, and lack of an obvious optical counterpart, 1E 161348-5055 defies assignment to any known class of X-ray sources. Starting from April 2006, Swift observed 1E 161348-5055 with its X-ray telescope for 2 ks approximately once per month. During the five years covered, the source has remained in a quiescent state, with an average observed flux of 1.7e-12 erg/cm^2/s (1-10 keV), about 20 times lower than the historical maximum attained in its 1999-2000 outburst. The long time-span of the Swift data allows us to obtain an accurate measure of the period of 1E 161348-5055 [P = 24030.42(2) s] and to derive the first upper limit on its period derivative (|dP/dt| < 1.6e-9 s/s at 3 sigma).