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Showing results for: [ Bhat, Ramesh ]
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 23 Feb 2020
Australia Telescope National Facility - P456 - A millisecond pulsar timing array - Published 22 Feb 2020
We propose timing observations of the relativistic pulsar - white-dwarf binary PSR J1141-6545. This unique system offers access to a wide range of physics, from relativistic phenomena through pulsar e... moremission cone studies, to the structure and distribution of interstellar plasma along our line-of-sight. The recently installed Parkes Ultra Wide Band Low Frequency (UWL) receiver has opened up the possibility of performing first-ever studies of its orbital dynamics at high temporal resolution and study of the effects of the intra-binary medium on the dispersion and polarisation of the pulse profile. Our analysis of data obtained to date suggests that the pulsar would precess away from our line-of-sight in the next 3-5 years. Hence, regular observations are crucial to maximizing its science outcomeless
Australia Telescope National Facility - P971 - Orbital dynamics and the intra-binary medium of PSR J1141-6545 - Published 22 Feb 2020
Australia Telescope National Facility - P456 - A millisecond pulsar timing array - Published 21 Feb 2020
Australia Telescope National Facility - P456 - A millisecond pulsar timing array - Published 20 Feb 2020
Australia Telescope National Facility - P456 - A millisecond pulsar timing array - Published 17 Feb 2020
Australia Telescope National Facility - P971 - Orbital dynamics and the intra-binary medium of PSR J1141-6545 - Published 15 Feb 2020
Australia Telescope National Facility - P971 - Orbital dynamics and the intra-binary medium of PSR J1141-6545 - Published 15 Jan 2020
Australia Telescope National Facility - P971 - Orbital dynamics and the intra-binary medium of PSR J1141-6545 - Published 08 Jan 2020
Australia Telescope National Facility - P456 - A millisecond pulsar timing array - Published 29 Dec 2019
The popular carousel model used to explain subpulse drifting in pulsars is criticised on both physical and empirical grounds. In the absence of relativistic effects (aberration and retardation, AR), i... moret predicts that subpulses undergo only amplitude modulation (i.e. no phase modulation) as a function of frequency. A recently advanced model incorporates AR effects and predicts a subpulse phase shift whose magnitude depends crucially on the assumption of the carousel model that the subpulses originate in discrete structures (sparks) that exist very close to the pulsar's surface. We propose to test this theory by measuring the subpulse phase shift of three pulsars which all exhibit different kinds of frequency evolution of their profiles. This requires both high time resolution of single-pulse data and a wide frequency band, as uniquely offered by the UWL. Our primary target (B1857-26) satisfies all of the conditions required by the proposed test. Two other targets (B1944+17 and B2003-08) also offer unique opportunities to study frequency-dependent subpulse phase shifting in the presence of rare phenomena relating to profile evolution and subpulse drifting. We anticipate that the study of these three pulsars will enable us to conclusively determine whether the carousel model and AR effects are able to account for the frequency-dependent behaviour of individual subpulses.less
Australia Telescope National Facility - P1030 - The frequency-dependent phase shifts of subpulses due to relativistic effects - Published 18 Dec 2019
Australia Telescope National Facility - P1030 - The frequency-dependent phase shifts of subpulses due to relativistic effects - Published 17 Dec 2019
Australia Telescope National Facility - P971 - Orbital dynamics and the intra-binary medium of PSR J1141-6545 - Published 14 Dec 2019
Australia Telescope National Facility - P971 - Orbital dynamics and the intra-binary medium of PSR J1141-6545 - Published 12 Dec 2019
Australia Telescope National Facility - P456 - A millisecond pulsar timing array - Published 17 Nov 2019
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 15 Nov 2019
Australia Telescope National Facility - P456 - A millisecond pulsar timing array - Published 13 Nov 2019
SUPERBx looks at the highest Galactic latitudes in a search for pulsars and fast radio bursts (FRBs). We use optimised GPU codes and supercomputing to search for these, making discoveries in real time... more. Handling our data as it comes in is essential for the SKA Phase I era so this work applies directly to the high-data rates of next generation telescopes. Our pulsar discoveries are typically nearby scintillating sources, intermittent sources and those in interesting binary systems. Our FRB discoveries have discovery lags of ~1 second, rather than months/years and these feed rapid alerts to the world-wide follow-up community via a dedicated VOEvent format an Astronomer's Telegrams. The goal of this is to allow localisation of the discovered FRBs. This is key for identifying FRB host galaxies, so as to solve the mystery of their progenitors and to exploit their many uses as tools for precision cosmology measurements.less
Australia Telescope National Facility - P892 - SUPERBx - The SUrvey for Pulsars & Extragalactic Radio Bursts Extension - Published 07 Nov 2019
Australia Telescope National Facility - P456 - A millisecond pulsar timing array - Published 07 Nov 2019
Australia Telescope National Facility - P971 - Orbital dynamics and the intra-binary medium of PSR J1141-6545 - Published 04 Nov 2019
Australia Telescope National Facility - P456 - A millisecond pulsar timing array - Published 31 Oct 2019
Australia Telescope National Facility - P456 - A millisecond pulsar timing array - Published 29 Oct 2019
Australia Telescope National Facility - P971 - Orbital dynamics and the intra-binary medium of PSR J1141-6545 - Published 22 Oct 2019
Australia Telescope National Facility - P971 - Orbital dynamics and the intra-binary medium of PSR J1141-6545 - Published 17 Oct 2019
