A dragon out of breath? Monitoring high-velocity outflows from the high-mass gamma-ray binary LS 2883/PSR B1259-63 during the 2017--2021 binary cycle

TL;DR

This study used Chandra X-ray observations to monitor high-velocity outflows from the gamma-ray binary LS 2883/PSR B1259-63 across multiple binary cycles, revealing variable ejection phenomena and suggesting changes in the Be star's disk influence outflow behavior.

Contribution

First systematic X-ray monitoring during the 2017--2021 cycle, highlighting differences in outflow features compared to previous cycles and exploring potential causes.

Findings

Extended emission observed in some observations, unlike previous clumps.

No bright moving clumps detected in 2017--2021 cycle.

Variability possibly linked to changes in the Be star's decretion disk.

Abstract

Observations of the high-mass gamma-ray binary LS 2883/PSR B1259--63 with the Chandra X-ray Observatory during the 2011--2014 and 2014--2017 binary cycles have shown X-ray emitting clumps, presumably ejected from the binary during periastron passages. These clumps traveled at projected velocities of $\sim0.1 c$ and have shown evidence of being accelerated. The clumps also evolved in shape, size, and flux. We monitored this binary with Chandra during the 2017--2021 binary cycle to search for additional X-ray emitting ejections. While we find evidence of extended emission in two of the six observations, it is unlike the clumps observed in the previous three binary cycles. More specifically, the extended emission is not well localized and no bright clump is observed moving away from the binary. It is still unclear what caused the lack of X-ray emitting clump in this orbital cycle, but it may be due to changes in the decretion disk of the Be star.