Revealing the state transition of Cen X-3 at high spectral resolution with Chandra

Abstract

Cen X-3 is a compact, high-mass X-ray binary (HMXRB), likely powered by Roche lobe overflow. We present a phase-resolved X-ray spectral and timing analysis of a target of opportunity \textit{Chandra} observation made during a low-flux to high-flux transition. The high-resolution spectra allow us to delve into the events that occurred during this episode. The spectrum is described by a single black body absorbed by a local column density of the order of $10^{23-24}$ cm${}^{-2}$, which is one to two orders of magnitude higher than found for previous analyses of data taken at similar orbital phases. Such a large column produces a Compton shoulder in the Fe K$\alpha$ line. The transition appears to be caused by the onset of efficient cooling, which cools the plasma by 10 million degrees in just 10 ks, allowing matter to enter the magnetosphere. This happens after a major disturbance, probably the arrival of a train of wind clumps with individual masses in the range $10^{19-20}$ g. This train moves ballistically in an eccentric orbit around the NS, producing a distinctive Doppler modulation in the \ion{Fe}{xxv} line.

References in corpus (7)

• The ephemeris, orbital decay, and masses of 10 eclipsing HMXBs
• Towards a unified view of inhomogeneous stellar winds in isolated supergiant stars and supergiant high mass X-ray binaries
• Determination of the mass of the neutron star in SMC X-1, LMC X-4 and Cen X-3 with VLT/UVES
• Pulse phase resolved analysis of the HMXB Cen X-3 over two binary orbits
• Quasiperiodic oscillations in Cen X-3 and the long term intensity variations
• X-ray variability of the HMXB Cen X-3: evidence for inhomogeneous accretion flows
• Discovery of Two Cyclotron Resonance Scattering Features in X-ray Pulsar Cen X-3 by Insight-HXMT

Cited by in corpus (2)

• XMM-Newton view of pulsating iron fluorescent emission from Centaurus X3
• High-resolution X-ray spectroscopy of Cen X-3 with XMM-Newton