4 pages, 4 figures, to be published in Proceedings of Electromagnetic Radiation from Pulsars and Magnetars, Zielona Góra, 2012, Astronomical Society of the Pacific Conference Series
Pulse nulling is one of many single pulse phenomena exhibited by radio pulsars. The broadband nature of this phenomena remained unexplained due to lack of coordinated observations. We are reporting broadband nulling behaviour of a well known nulling pulsar PSR B2319+60. The simultaneous observations were carried out at four different frequencies using the Giant Meterwave Radio telescope (325 and 610 MHz), the Westerbork Synthesis Radio Telescope (1420 MHz) and the Effelsberg radio telescope (5100 MHz). The nulling fractions were estimated at all four observed frequencies, which suggest similar degree of nulling across these frequencies. To comment on the broadband behaviour of pulse nulling, we calculated the Pearson cross-correlation coefficients for the occurrence of null and burst pulses between all four frequencies. We conclude that nulling is largely a broadband phenomenon for this pulsar and it points towards a global failure of the magnetospheric currents which produces radio emission at these frequencies.
Several pulsars show sudden cessation of pulsed emission, which is known as nulling. The number of known nulling pulsars has not been significantly enhanced in the last decade, although the pulsar population has more than doubled following the Parkes multi-beam pulsar survey. A systematic follow-up study of the new pulsars, discovered in this survey, is being carried out by us at 325-MHz with GMRT. The peculiar nulling behaviour of PSR J1738-2330, observed as a part of this 325-MHz GMRT survey, is reported in this paper. The pulsar appears to show a periodic null-burst cycle with an upper limi…
PSR J1717-4054 is one of the small class of pulsars which null on intermediate (~hour) timescales. Such pulsars represent an important link between classical nullers, whose emission vanishes for a few rotations, and the intermittent pulsars which null for months and years. Using the Parkes radio telescope and the Australia Telescope Compact Array, we have studied the emission from PSR J1717-4054 over intervals from single pulses to years. We have identified and characterised nulling at three discrete timescales: the pulsar emits during "active states" separated by nulls lasting many thousands …
We report on the unique nulling properties of PSR B0818-41, using the GMRT at 325 and 610 MHz. We find following interesting behaviour just before and after the nulls: (i) The pulsar's intensity does not switch off abruptly at the null, but fades gradually, taking ~ 10 P1. Just after nulls intensity rises to a maximum over a short (less than one period) time scale. (ii) While the last active pulses before nulls are dimmer, the first few active pulses just after nulls outshine normal ones. This effect is very clear for inner region of pulsar profile, where mean intensity of last few active puls…
Single pulse observations, characterizing in detail, the nulling behaviour of PSR B1706$-$16 are being reported for the first time in this paper. Our regular long duration monitoring of this pulsar reveals long nulls of 2 to 5 hours with an overall nulling fraction of 31$\pm$2\%. The pulsar shows two distinct phases of emission. It is usually in an active phase, characterized by pulsations interspersed with shorter nulls, with a nulling fraction of about 15 \%, but it also rarely switches to an inactive phase, consisting of long nulls. The nulls in this pulsar are concurrent between 326.5 and …
We performed simultaneous observations at 326.5 MHz with the Ooty Radio Telescope and at 326, 610 and 1308 MHz with the Giant Meterwave Radio Telescope for a sample of 12 pulsars, where frequency dependent single pulse behaviour was reported. The single pulse sequences were analysed with fluctuation analysis, sensitive to both the average fluctuation properties (using longitude resolved fluctuation spectrum and two-dimensional fluctuation spectrum) as well as temporal changes in these (using sliding two-dimensional fluctuation spectrum ) to establish concurrent changes in subpulse drifting ove…
Several pulsars show sudden cessation of pulsed emission, which is known as pulsar nulling. In this paper, the nulling behaviour of 15 pulsars is presented. The nulling fractions of these pulsars, along with the degree of reduction in the pulse energy during the null phase, are reported for these pulsars. A quasi-periodic null-burst pattern is reported for PSR J1738-2330. The distributions of lengths of the null and the burst phases as well as the typical nulling time scales are estimated for eight strong pulsars. The nulling pattern of four pulsars with similar nulling fraction are found to b…
We have studied the variability of PSR J0529-6652, a radio pulsar in the LMC, using observations conducted at 1390 MHz with the Parkes 64-m telescope. PSR J0529-6652 is detectable as a single pulse emitter, with amplitudes that classify the pulses as giant pulses. This makes PSR J0529-6652 the second known giant pulse emitter in the LMC, after PSR B0540-69. The fraction of the emitted pulses detectable from PSR J0529-6652 at this frequency is roughly two orders of magnitude greater than it is for either PSR B0540-69 or the Crab pulsar (if the latter were located in the LMC). We have measured a…
This paper compares and contrasts the emission of two high nulling fraction pulsars, PSRs J1738-2330 and J1752+2359. In both pulsars the emission bursts appear in a quasi-periodic fashion with typical separations of several hundred pulses, and in J1738-2330 there is evidence of two underlying periodicities with memory persisting for at least 11 bursts. By contrast, in J1752+2359 the pattern coherence is rapidly lost and the burst/null lengths appear to be selected randomly from their respective quasi-normal distributions. The typical emission bursts of J1738-2330 exhibit a steady exponential d…
Institute for Gravitational Wave Astronomy and School of Physics and Astronomy, University of Birmingham（伯明翰大学引力波天文研究所与物理天文学学院）；Quantum Formatics（量子计算公司）；Department of Physics and Astronomy, West Virginia University（西弗吉尼亚大学物理与天文学系）；Center for Gravitational Waves and Cosmology, West Virginia University（西弗吉尼亚大学引力波与宇宙学中心）；Department of Physics, Indian Institute of Science Education and Research Bhopal（印度科学教育研究学院博帕尔分校物理系）
PSR B0823+26, a 0.53-s radio pulsar, displays a host of emission phenomena over timescales of seconds to (at least) hours, including nulling, subpulse drifting, and mode-changing. Studying pulsars like PSR B0823+26 provides further insight into the relationship between these various emission phenomena and what they might teach us about pulsar magnetospheres. Here we report on the LOFAR discovery that PSR B0823+26 has a weak and sporadically emitting 'quiet' (Q) emission mode that is over 100 times weaker (on average) and has a nulling fraction forty-times greater than that of the more regularl…
Simultaneous observations at four different frequencies viz. 313, 607, 1380 and 4850 MHz, for three pulsars, PSRs B0031-07, B0809+74 and B2319+60, are reported in this paper. Identified null and burst pulses are highly concurrent across more than decade of frequency. Small fraction of non-concurrent pulses (less than or equal to 3%) are observed, most of which occur at the transition instances. We report, with very high significance for the first time, full broadband nature of the nulling phenomenon in these three pulsars. These results suggest that nulling invokes changes on the global magnet…
We present the results of wide-band (720-2400 MHz) study of PSR B1821-24A (J1824-2452A, M28A), an energetic millisecond pulsar visible in radio, X-rays and gamma-rays. In radio, the pulsar has a complex average profile which spans >85% of the spin period and exhibits strong evolution with observing frequency. For the first time we measure phase-resolved polarization properties and spectral indices of radio emission throughout almost all of the on-pulse window. We combine this knowledge with the high-energy information to compare M28A to other known gamma-ray millisecond pulsars and to speculat…
We present the results of a search for transient radio bursts of between 0.125 and 32 millisecond duration in two archival pulsar surveys of intermediate galactic latitudes with the Parkes multibeam receiver. Fourteen new neutron stars have been discovered, seven of which belong to the recently identified "rotating radio transients" (RRATs) class. Here we describe our search methodology, and discuss the new detections in terms of how the RRAT population relates to the general population of pulsars. The new detections indicate (1) that the galactic z-distribution of RRATs in the surveys closely…
We present the discovery and timing solutions of five new pulsars by students involved in the Pulsar Search Collaboratory (PSC), a NSF-funded joint program between the National Radio Astronomy Observatory and West Virginia University designed to excite and engage high-school students in Science, Technology, Engineering, and Mathematics (STEM) and related fields. We encourage students to pursue STEM fields by apprenticing them within a professional scientific community doing cutting edge research, specifically by teaching them to search for pulsars. The students are analyzing 300 hours of drift…
We show the results of microsecond resolution radio data analysis focused on flux measurements of single pulses of PSR B1133+16. The data were recorded at 4.85 GHz and 8.35 GHz with 0.5 GHz and 1.1 GHz bandwidth, respectively, using Radio Telescope Effelsberg (MPIfR). The most important conclusion of the analysis is, that the strongest single pulse emission at 4.85 GHz and 8.35 GHz contributes almost exclusively to the trailing part of the leading component of the pulsar mean profile, whereas studies at lower frequencies report that the contribution is spread almost uniformly covering all phas…
PSR B0943+10 is an old non-recycled pulsar which for decades has been mostly known for its rapid and spontaneous radio mode switching. Recently, Hermsen et al. (2013) discovered correlated changes in the thermal X-ray emission from the polar cap, thus demonstrating that radio modes are not just a product of the local changes in the radio emission region, but a sign of some global magnetospheric transformation. At about the same time, owing to the commissioning of the new generation of low-frequency radio arrays, the broadband observations at the lowest edge of ionospheric transparency window b…
We describe system verification tests and early science results from the pulsar processor (PTUSE) developed for the newly-commissioned 64-dish SARAO MeerKAT radio telescope in South Africa. MeerKAT is a high-gain (~2.8 K/Jy) low-system temperature (~18 K at 20cm) radio array that currently operates from 580-1670 MHz and can produce tied-array beams suitable for pulsar observations. This paper presents results from the MeerTime Large Survey Project and commissioning tests with PTUSE. Highlights include observations of the double pulsar J0737-3039A, pulse profiles from 34 millisecond pulsars fro…
We report on the pulse-to-pulse energy distributions and phase-resolved modulation properties for catalogued pulsars in the southern High Time Resolution Universe intermediate-latitude survey. We selected the 315 pulsars detected in a single-pulse search of this survey, allowing a large sample unbiased regarding any rotational parameters of neutron stars. We found that the energy distribution of many pulsars is well-described by a log-normal distribution, with few deviating from a small range in log-normal scale and location parameters. Some pulsars exhibited multiple energy states correspondi…
High-sensitivity radio-frequency observations of millisecond pulsars usually show stochastic, broadband, pulse-shape variations intrinsic to the pulsar emission process. These variations induce jitter noise in pulsar timing observations; understanding the properties of this noise is of particular importance for the effort to detect gravitational waves with pulsar timing arrays. We assess the short-term profile and timing stability of 22 millisecond pulsars that are part of the Parkes Pulsar Timing Array sample by examining intra-observation arrival time variability and single-pulse phenomenolo…
We extend profile domain pulsar timing to incorporate wide-band effects such as frequency-dependent profile evolution and broadband shape variation in the pulse profile. We also incorporate models for temporal variations in both pulse width and in the separation in phase of the main pulse and interpulse. We perform the analysis with both nested sampling and Hamiltonian Monte Carlo methods. In the latter case we introduce a new parameterisation of the posterior that is extremely efficient in the low signal-to-noise regime and can be readily applied to a wide range of scientific problems. We app…
