1870002

In X-ray binary systems either a neutron star or a black hole accretes matter from an orbiting companion star. This accretion process often powers the launch of powerful relativistic collimated outflows called jets. While this connection between inflow and outflow is observed in systems ranging from forming stars to AGN jet formation remains poorly understood. Neutron stars in X-ray binaries offer a unique avenue to understand this process: as accreted material accumulates on the neutron star surface it can cause bursts of X-ray emission through runaway thermonuclear burning. The thermonuclear bursts can cool the surrounding structures such as the base of the jet. While these effects have been predicted from simulations such a response of the jet to thermonuclear bursts has never been observed directly.Our team have scheduled Australia Telescope Compact Array (ATCA) radio observations of an accreting neutron star to search for a response of the jet (brightness and morphology) to thermonuclear bursts. We have arranged with the INTEGRAL team to set up a simultaneous X-ray observation in order to measure when thermonuclear bursts occur for which we put in this official ToO. Comparing the INTEGRAL burst times with the radio light curve we will be able to test whether the jet responds by for instance briefly decreasing in power or by changing its spectrum. It will also reveal possible time delays between the X-ray and radio band probing the physical structure and size scales of the jet. The ATCA observations are planned for April 3 4 and 5 overlapping exactly with revolution 2350 of INTEGRAL. On April 3 they start at 12.30 GMT allowing for calibration before the start of the INTEGRAL revolution (at 13.18 GMT). The selected target is 4U 1728-34. [truncated! Please see actual data for full text]