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Showing results for: [ Dempsey, James ]
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 o... moreur understanding of Solar-system dynamics. The PPTA is the oldest of three international pulsar timing groups. We have the smallest telescope and the smallest group, but the best measurements and the best results. Our bound on the strength of the incoherent gravitational wave background is the only bound which significantly constrains theoretical models. We have maintained our leading position because: we have the southern sky; we have a small but well-focussed group; we have the best-calibrated receivers; and we have been able to observe with an almost regular cadence of 15 to 20 days over a wide bandwidth. With this proposal we aim to maintain our pre-eminent position in the field. Unlike most observing proposals, this is a continuing proposal for which the observations will continue to improve bounds on ultra-low-frequency gravitational waves until they are finally detected. 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 we will want to continue observations in support of the nascent field of gravitational wave astronomy!less
Australia Telescope National Facility - P456 - A millisecond pulsar timing array - Published 21 Jul 2020
This proposal relates to time purchased by the Chinese Academy of Sciences for Parkes follow-up confirmation and timing of FAST discoveries. As the observing time has been purchased this proposal (an... mored the related PX501) does not require TAC grading. The primary reason for submitting a proposal is to ensure an outreach statement and that the proposal is entered into OPAL for the data archive to access. The Chinese team have two time requests. The time scheduled for the first, relating to this proposal, will be allocated in blocks of 24 hours and the data will become available in the data archive with an 18 month embargo period. The second type of time will be scheduled in shorter blocks and the data archived with a 10 year embargo.less
Australia Telescope National Facility - PX500 - FAST: category 1 purchased time - Published 23 Jun 2020
We report the direct detection of cold HI gas in a cloud ejected from the Small Magellanic Cloud (SMC) towards the Magellanic Stream. The cloud is part of a fragmented shell of HI gas on the outskirt... mores of the SMC. This is the second direct detection of cold HI associated with the Magellanic Stream using absorption. The cold gas was detected using 21-cm HI absorption-line observations with the Australia Telescope Compact Array (ATCA) towards the extra-galactic source PMN J0029-7228. We find a spin (excitation) temperature for the gas of 68+-20 K. We suggest that breaking super shells from the Magellanic Clouds may be a source of cold gas to supply the rest of the Magellanic Stream.less
Australia Telescope National Facility - C3297 - Follow-up observations of HI absorption near the SMC detected by ASKAP - Published 17 Jun 2020
Australia Telescope National Facility - P456 - A millisecond pulsar timing array - Published 31 May 2020
This proposal relates to time purchased by the Chinese Academy of Sciences for Parkes follow-up confirmation and timing of FAST discoveries. As the observing time has been purchased this proposal (an... mored the related PX500) does not require TAC grading. The primary reason for submitting a proposal is to ensure an outreach statement and that the proposal is entered into OPAL for the data archive to access. The Chinese team have two time requests. The time scheduled for the first (PX500) will be allocated in blocks of 24 hours and the data will become available in the data archive with an 18 month embargo period. The second type of time (relating to this proposal) will be scheduled in shorter blocks and the data archived with a 10 year embargo.less
Australia Telescope National Facility - PX501 - FAST: category 2 purchased time - Published 25 May 2020
Australia Telescope National Facility - PX500 - FAST: category 1 purchased time - Published 11 May 2020
After five decades of study, the physics of radio wave emission and propagation in the pulsar magnetosphere remains poorly understood. This is largely due to the wide variety of dynamic phenomena obs... moreerved in pulsar signals that are neither predicted nor explained by current theory, the limited window of the pulsar spectrum that previously could be studied simultaneously, and the biased sample of the pulsar population that has been studied to date. To address these limitations, we have developed pioneering statistical methods that provide new interpretive insights and enable us to study the dynamics of the radio pulsar signal on short time scales (e.g. drifting and quasi-periodic sub-pulse structure, transitions between orthogonally polarized modes of emission, nulling, etc.) even when individual pulses cannot be detected. Using our novel methods and the ultra-wide bandwidth receiver at Parkes, we will undertake a large-scale survey of pulsar radio emission statistics and explore two previously inaccessible regions where pulsar flux densities are typically much lower: the pulsar spectrum above 2 GHz, and the recycled pulsar population. Measuring the instantaneous bandwidth of impulsive emission events will yield new constraints on the physical conditions in the pulsar magnetosphere, such as the spatial scale of strong turbulence in the magnetospheric plasma. The breadth of our sample, from millisecond pulsars to magnetars, will enable us to study the evolution of emission and propagation physics over four orders of magnitude in magnetospheric size and seven orders of magnitude in magnetic field strength.less
Australia Telescope National Facility - P1052 - Pulsar Radio Emission Statistics Survey (PRESS) - Published 11 May 2020
Australia Telescope National Facility - P456 - A millisecond pulsar timing array - Published 08 May 2020
These observations will form part of the ASKAP pilot survey program. This is a joint exercise between CASS and the ASKAP Survey Science Teams to conduct a series of observations to learn how to conduc... moret large-scale surveys using the full capabilities of this new telescope. The key goal of the pilot survey program is to establish readiness for full survey operations, including determining and testing observing and processing strategies, and data validation and release. The observations collected here are primarily for GASKAP.less
Australia Square Kilometre Array Pathfinder - AS108 - ASKAP Pilot Survey for GASKAP - Published 01 May 2020
Australia Telescope National Facility - P456 - A millisecond pulsar timing array - Published 26 Apr 2020
Australia Telescope National Facility - PX500 - FAST: category 1 purchased time - Published 26 Apr 2020
Australia Telescope National Facility - PX501 - FAST: category 2 purchased time - Published 23 Apr 2020
Australia Telescope National Facility - PX500 - FAST: category 1 purchased time - Published 18 Apr 2020
Australia Telescope National Facility - PX501 - FAST: category 2 purchased time - Published 12 Apr 2020
Australia Telescope National Facility - P456 - A millisecond pulsar timing array - Published 11 Apr 2020
Since the year 2005, the Parkes Pulsar Timing Array (PPTA) project has been placing ever more stringent constraints on the amplitude of a gravitational wave background signal. Such upper bounds on th... moree amplitude of the gravitational wave signal are currently dominated by a single pulsar: PSR J1909-3744. The upper bound with this pulsar alone already cuts into the range of tenable theoretical models. Further reducing the amplitude bound (by continued regular observations of this pulsar) will significantly narrow that range. The first evidence of gravitational waves in the pulsar data are likely to be observed in the timing for PSR J1909-3744, but with only a single pulsar we will not be able to make an unambiguous detection. However, knowledge of the likely signal strength (derived from this pulsar) will help to optimise the observing strategy for the detection of the gravitational wave signals with existing or future pulsar timing arrays.less
Australia Telescope National Facility - P895 - Where are the gravitational waves? - Published 11 Apr 2020
Australia Telescope National Facility - P895 - Where are the gravitational waves? - Published 09 Apr 2020
Australia Telescope National Facility - PX501 - FAST: category 2 purchased time - Published 05 Apr 2020
Australia Telescope National Facility - P456 - A millisecond pulsar timing array - Published 31 Mar 2020
Australia Telescope National Facility - PX500 - FAST: category 1 purchased time - Published 31 Mar 2020
Australia Telescope National Facility - P895 - Where are the gravitational waves? - Published 31 Mar 2020
Australia Telescope National Facility - P456 - A millisecond pulsar timing array - Published 24 Mar 2020
