A radio study of the optically-discovered black hole X-ray binary AT2019wey

Project Description:

In 2019 the optical transient source AT2019wey was discovered by the ATLAS telescope. It was soon realised that this was a rare example of a previously unknown accreting stellar mass black hole in a binary system being discovered in the optical band. This optical emission arises from the outer accretion disc around the black hole, and the rapid rise in optical emission indicates an accretion-driven outburst. Subsequent observations identified the expected X-ray (inner accretion disc) and radio (relativistic jet) counterparts. The system is very interesting for a number of reasons: - AT2019wey has one of the shortest-period black hole candidates known (~2.7 hr). There are hints that the behaviour of X-ray binaries at very short orbital periods differ from the norm. The short orbital period also implies a very low-mass donor (≲0.3 M☉). - It had a hard-state–dominated outburst, possibly a failed state transition, although in the past year it may have undergone for the first time a ‘traditional’ hard-to-soft state transition (or indeed multiple transitions, resulting in strong flares). - The early optical detection, providing a rare opportunity to see catch the rising phase of the outburst, as mass accretion rate increased and the accretion disc brightened. - The high galactic latitude and measured proper motions strongly support an origin for the black hole in a supernova explosion which provided a natal kick. At Oxford, via our long-running transients programme on the AMI-LA radio telescope, we have made approximately 100 radio observations, with a large number of detections, and data acquisition is still ongoing. These data have not to date been published in any form. Analysis of these data and comparison to X-ray and optical data obtained with other facilities will allow us to understand the production and energetics of the relativistic jet in this system. This is the key goal of this project: reduction and analysis of the AMI-LA data, and then using them in the broader context of existing knowledge and other observations to piece together the astrophysics of what is going on in this system. The teams associated with both supervisors have extensive experience with all aspects of the project.

Research Area:

Astronomy

Project Level:

Masters

This Project Is Offered At The Following Node(s):

(UCT)