Artist's impression of the neutron star GS 1826–24, accreting material from its neighbor in a disk, and undergoing a bright thermonuclear burst that sends a flash through the system, illuminating its different components. Image credit: Futselaar (artsource) / Degenaar. Download Image
During the past week, NuSTAR targeted the X-ray binary GS 1826–24 in coordinated observations with the Karl G. Jansky Very Large Array (VLA) radio telescope, aiming to directly measure the speed of a jet launched by an accreting neutron star. This source recently entered an extraordinary state of rapid, clocklike thermonuclear bursts ignited on the neutron star surface. This produces a series of predictable, high-contrast, X-ray flashes that perturb the inner accretion flow and the associated jet of the neutron star binary system. NuSTAR precisely measures the burst onset and energetics, as well as the dynamical response of the inner accretion flow, while the VLA simultaneously tracks the compact radio jet. By measuring the lag between the X-ray burst and the jet’s radio response, the jet propagation speed can be directly determined — applying a novel burst-timing technique that was recently first demonstrated by the same team to measure the speed of the compact jet of the accreting neutron star 4U 1728−34 . At the same time, NuSTAR’s broadband X-ray coverage tracks how different components of the accretion flow — such as the boundary layer, corona, and inner disk — respond to each burst. This approach tests fundamental predictions for how relativistic jets are launched and powered in accreting compact objects.
During the past week, NuSTAR targeted the X-ray binary GS 1826–24 in coordinated observations with the Karl G. Jansky Very Large Array (VLA) radio telescope, aiming to directly measure the speed of a jet launched by an accreting neutron star. This source recently entered an extraordinary state of rapid, clocklike thermonuclear bursts ignited on the neutron star surface. This produces a series of predictable, high-contrast, X-ray flashes that perturb the inner accretion flow and the associated jet of the neutron star binary system. NuSTAR precisely measures the burst onset and energetics, as well as the dynamical response of the inner accretion flow, while the VLA simultaneously tracks the compact radio jet. By measuring the lag between the X-ray burst and the jet’s radio response, the jet propagation speed can be directly determined — applying a novel burst-timing technique that was recently first demonstrated by the same team to measure the speed of the compact jet of the accreting neutron star 4U 1728−34 . At the same time, NuSTAR’s broadband X-ray coverage tracks how different components of the accretion flow — such as the boundary layer, corona, and inner disk — respond to each burst. This approach tests fundamental predictions for how relativistic jets are launched and powered in accreting compact objects.
Author: Nathalie Degenaar (Associate Professor, University of Amsterdam)
