This project is to continue timing and profile studies of the first double-pulsar system, a unique laboratory for gravitational physics. Important results published in our 53-page Phys. Rev. X paper (2021) include the first measurements of higher-order light-propagation effects and of the relativistic deformation of the orbit and highlight the importance of a long term observational campaign, including VLBI observations, for this remarkable system. The main aims of this proposal are to provide the strongest tests to date for general relativity and to measure for the first time the moment-of-inertia of a neutron star. Additionally, we will determine the system geometry, map the pulsar beams via geodetic precession, and search for the reappearance of Pulsar B. We exploit the high sensitivity and broad bandwidth of the UWL receiver. We are collaborating with the MeerKAT Double Pulsar Timing team to optimise combination of MeerKAT and UWL data.

This project is to continue timing and profile studies of the first double-pulsar system, a unique laboratory for gravitational physics. Important results published in our 53-page Phys. Rev. X paper (2021) include the first measurements of higher-order light-propagation effects and of the relativistic deformation of the orbit and highlight the importance of a long term observational campaign, including VLBI observations, for this remarkable system. The main aims of this proposal are to provide the strongest tests to date for general relativity and to measure for the first time the moment-of-inertia of a neutron star. Additionally, we will determine the system geometry, map the pulsar beams via geodetic precession, and search for the reappearance of Pulsar B. We exploit the high sensitivity and broad bandwidth of the UWL receiver. We are collaborating with the MeerKAT Double Pulsar Timing team to optimise combination of MeerKAT and UWL data.

With this proposal, we aim to continue P1032, the rapid measurements of relativistic parameters of southern binary pulsar systems using data from the Parkes Ultra Wideband Low (UWL) receiver. As the MeerTime project at the MeerKAT radio telescope ended in early 2024, observations with the UWL receiver now form the backbone for extending the timing baselines of many pulsars that have been part of this project. Since the source selection in the previous semesters was tailored such that the UWL receiver is the most (versatile and) suited instrument to achieve the proposed scientific goals for the chosen pulsars, we propose to continue these observations. We will use the UWL data to obtain significant orbital coverage and timing baselines on these pulsars and obtain important constraints on orbital and temporal DM variations that will help in identifying the nature of the companion stars. Increasing the number of measured Neutron Star (NS) masses, as well as improving on current constraints has profound implications for NS internal structure and for stellar and binary evolution physics.

With this proposal, we aim to continue P1032, the rapid measurements of relativistic parameters of southern binary pulsar systems using data from the Parkes Ultra Wideband Low (UWL) receiver. As the MeerTime project at the MeerKAT radio telescope ended in early 2024, observations with the UWL receiver now form the backbone for extending the timing baselines of many pulsars that have been part of this project. Since the source selection in the previous semesters was tailored such that the UWL receiver is the most (versatile and) suited instrument to achieve the proposed scientific goals for the chosen pulsars, we propose to continue these observations. We will use the UWL data to obtain significant orbital coverage and timing baselines on these pulsars and obtain important constraints on orbital and temporal DM variations that will help in identifying the nature of the companion stars. Increasing the number of measured Neutron Star (NS) masses, as well as improving on current constraints has profound implications for NS internal structure and for stellar and binary evolution physics.

With this proposal, we aim to continue P1032, the rapid measurements of relativistic parameters of southern binary pulsar systems using data from the Parkes Ultra Wideband Low (UWL) receiver. As the MeerTime project at the MeerKAT radio telescope ended in early 2024, observations with the UWL receiver now form the backbone for extending the timing baselines of many pulsars that have been part of this project. Since the source selection in APRS2024 was tailored such that the UWL receiver is the most (versatile and) suited instrument to achieve the proposed scientific goals for the chosen pulsars, we propose to continue these observations. We will use the UWL data to obtain significant orbital coverage and timing baselines on these pulsars and obtain important constraints on orbital and temporal DM variations that will help in identifying the nature of the companion stars. Increasing the number of measured Neutron Star (NS) masses, as well as improving on current constraints has profound implications for NS internal structure and for stellar and binary evolution physics. We request pre-graded status for this project for the next semester.

With this proposal, we aim to continue P1032, the rapid measurements of relativistic parameters of southern binary pulsar systems using data from the Parkes Ultra Wideband Low (UWL) receiver. As the MeerTime project at the MeerKAT radio telescope ended in early 2024, observations with the UWL receiver now form the backbone for extending the timing baselines of many pulsars that have been part of this project. Since the source selection in APRS2024 was tailored such that the UWL receiver is the most (versatile and) suited instrument to achieve the proposed scientific goals for the chosen pulsars, we propose to continue these observations. We will use the UWL data to obtain significant orbital coverage and timing baselines on these pulsars and obtain important constraints on orbital and temporal DM variations that will help in identifying the nature of the companion stars. Increasing the number of measured Neutron Star (NS) masses, as well as improving on current constraints has profound implications for NS internal structure and for stellar and binary evolution physics. We request pre-graded status for this project for the next semester.

With this proposal, we aim to continue P1032, the rapid measurements of relativistic parameters of southern binary pulsar systems using data from the Parkes Ultra Wideband Low (UWL) receiver. As the MeerTime project at the MeerKAT radio telescope ended in early 2024, observations with the UWL receiver now form the backbone for extending the timing baselines of many pulsars that have been part of this project. Since the source selection in APRS2024 was tailored such that the UWL receiver is the most (versatile and) suited instrument to achieve the proposed scientific goals for the chosen pulsars, we propose to continue these observations. We will use the UWL data to obtain significant orbital coverage and timing baselines on these pulsars and obtain important constraints on orbital and temporal DM variations that will help in identifying the nature of the companion stars. Increasing the number of measured Neutron Star (NS) masses, as well as improving on current constraints has profound implications for NS internal structure and for stellar and binary evolution physics. We request pre-graded status for this project for the next semester.

The Parkes Pulsar Timing Array (PPTA) project has three primary goals: (a) detection of gravitational waves from astronomical sources, (b) establishment of a pulsar timescale, and (c) improvement of our understanding of Solar-system dynamics. We are now in an exciting regime where a signal detected in our (and other data sets) has the form expected for a gravitational wave background. We, along with the international community, are now working hard to either confirm or deny this result, and to determine the astrophysical origin of this signal. With this proposal, we aim to maintain our pre-eminent position in the field. This is a continuing proposal for which observations of millisecond pulsars (MSPs) will continue to improve bounds on ultra-low-frequency gravitational waves until they are detected with confidence. Continued Parkes observations will remain valuable at least until the first stage of the SKA is able to improve on our sensitivity and observing cadence. Even after the gravitational wave background is detected, continued observations will resolve the background origin and individual sources will be identified; advancing the nascent field of gravitational wave astronomy.

The Parkes Pulsar Timing Array (PPTA) project has three primary goals: (a) detection of gravitational waves from astronomical sources, (b) establishment of a pulsar timescale, and (c) improvement of our understanding of Solar-system dynamics. We are now in an exciting regime where a signal detected in our (and other data sets) has the form expected for a gravitational wave background. We, along with the international community, are now working hard to either confirm or deny this result, and to determine the astrophysical origin of this signal. With this proposal, we aim to maintain our pre-eminent position in the field. This is a continuing proposal for which observations of millisecond pulsars (MSPs) will continue to improve bounds on ultra-low-frequency gravitational waves until they are detected with confidence. Continued Parkes observations will remain valuable at least until the first stage of the SKA is able to improve on our sensitivity and observing cadence. Even after the gravitational wave background is detected, continued observations will resolve the background origin and individual sources will be identified; advancing the nascent field of gravitational wave astronomy.

We request time to observe 270 pulsars on a regular basis in order to achieve three main science goals. The first is to understand pulsars: how do they spin down and what disrupts this process, how and why their profiles vary with time, whether they precess or have planetary mass companions, in short all the things that make pulsar timing noisier than the perfect clock. Secondly we want to understand the interstellar medium of our Galaxy through repeated monitoring of dispersion measure, rotation measure and flux density variations in conjunction with scintillation parameters. Finally, we provide these data as a community service both to the high-energy community where we have strong collaborative links (particularly to Fermi) and to the radio pulsar astronomers generally through the CSIRO archive. The project is on-going since 2007, we are (co-)authors on 107 papers arising from the P574 data. The data have contributed to the PhD theses of students from Bordeaux, Manchester, Oxford, Stanford, and Swinburne. We are seeking long-term project status with a view to continuing the project into the SKA era.