Dynamic shocks and precessing jets from an enigmatic accreting neutron star

Abstract:

Circinus X-1 is an enigmatic accreting neutron star which defies conventional classification despite decades of study. Surrounded by its natal supernova remnant, aged at ~2900 years, it is the youngest known X-ray binary (XRB). I will show that new radio observations of this system with MeerKAT, combined with archival data from ATCA going back over 20 years, have allowed for unprecedented insight into the outflows in this system. In particular the first observation of precessing jets from an accreting neutron star, the discovery of parsec scale jets from a neutron star XRB, and the first observation of dynamic large scale structures in any XRB. These data allow for insights into a variety of different physics from accretion and jet launching, to PeV particle acceleration and ultra-fast outflows. Finally, I will highlight some more general recent results from the X-KAT program, particularly focussing on systematically probing radio polarisation in XRB jets for the first time.

The image above is a 2.6 GHz MeerKAT image in 2023 of Cir X-1 and its natal SNR, the Africa nebula. Structures of radio emission associated with the SNR and areas where the outflows from Cir X-1 interact with the surrounding region are visible. Cir X-1 and its precessing jets on parsec scales are seen as radio sources in the centre of the nebula. To the north-west and south-east asymmetric jet inflated bubbles are visible at the edge of the SNR. Image from Cowie et al. 2026.