Journal articles: 'Pulsar Search'

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Levin, L., W. Armour, C. Baffa, E. Barr, S. Cooper, R. Eatough, A. Ensor, et al. "Pulsar Searches with the SKA." Proceedings of the International Astronomical Union 13, S337 (September 2017): 171–74. http://dx.doi.org/10.1017/s1743921317009528.

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AbstractThe Square Kilometre Array will be an amazing instrument for pulsar astronomy. While the full SKA will be sensitive enough to detect all pulsars in the Galaxy visible from Earth, already with SKA1, pulsar searches will discover enough pulsars to increase the currently known population by a factor of four, no doubt including a range of amazing unknown sources. Real time processing is needed to deal with the 60 PB of pulsar search data collected per day, using a signal processing pipeline required to perform more than 10 POps. Here we present the suggested design of the pulsar search engine for the SKA and discuss challenges and solutions to the pulsar search venture.

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Michel, F. Curtis. "Statistical Search for Magnetic Field Decay." International Astronomical Union Colloquium 128 (1992): 35–38. http://dx.doi.org/10.1017/s000273160015471x.

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AbstractThe claims made in many statistical analyses for magnetic field decay follow from the assumption that radio luminosity declines slower than spin-down luminosity which is suggested by least-squares fits to the data. However, such fits are very sensitive to the behaviors of the fastest and slowest pulsars. If pulsar luminosities are plotted in distance-selected groups, the (radio inefficient) Crab and Vela pulsars are clearly exceptional members and the remaining pulsars are consistent with a mean fixed conversion efficiency of 10–5. Numerical simulations (and theoretical analysis) strongly suggest that the pulsar period distribution peak is caused by luminosity selection and searches limited in distance by dispersion measure, and not by some mechanism that removes old pulsars. We cannot exclude magnetic field decay with some large time constant, ≥107 years say, but only because it would make such a small difference to the expected pulsar statistics, not because it is required by the data.

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Octau, Franck, Grégory Desvignes, Ismaël Cognard, David Champion, Patrick Lazarus, David Smith, and Gilles Theureau. "Search for and study of pulsars with the Nançay Radio Telescope." Proceedings of the International Astronomical Union 13, S337 (September 2017): 386–87. http://dx.doi.org/10.1017/s1743921317009516.

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AbstractSince the discovery of the first pulsar in 1967, over 2500 pulsars have been discovered. Pulsars enable a broad range of studies: from the study of the properties of the interstellar medium and of pulsar magnetospheres to tests of gravity in the strong-field regime and the characterisation of the cosmological gravitation wave background. These reasons are the main drive for searching for more pulsars. A blind pulsar survey, named SPAN512, was initiated with the Nançay Radio Telescope in 2012. Conducted at 1.4 GHz with a sampling time of 64μs and 500-kHz frequency channels, SPAN512 was designed to search for fast and distant pulsars in the Galactic plane. Here we describe the current status of the survey and present the latest discovery, PSR J2055+3829, a 2.08-ms pulsar in a black widow system.

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Dai, Shi, Simon Johnston, and George Hobbs. "Searching for pulsars in future radio continuum surveys." Proceedings of the International Astronomical Union 13, S337 (September 2017): 328–29. http://dx.doi.org/10.1017/s1743921317008833.

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AbstractRadio continuum surveys are equally sensitive to all pulsars, not affected by dispersion measure smearing, scattering or orbital modulation of spin periods, and therefore allow us to search for extreme pulsars, such as sub-millisecond pulsars, pulsar-black hole systems and pulsars in the Galactic Centre. As we move towards the Square Kilometre Array (SKA) era, searching for pulsars in continuum images will complement conventional pulsar searches, and make it possible to find extreme objects.

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Sett, S., R. P. Breton, C. J. Clark, M. H. Kerkwijk, and D. L. Kaplan. "A search for radio pulsars in five nearby supernova remnants." Astronomy & Astrophysics 647 (March 2021): A183. http://dx.doi.org/10.1051/0004-6361/201936108.

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Context. Most neutron stars are expected to be born in supernovae, but only about half of supernova remnants (SNRs) are associated with a compact object. In many cases, a supernova progenitor may have resulted in a black hole. However, there are several possible reasons why true pulsar-SNR associations may have been missed in previous surveys: The pulsar’s radio beam may not be oriented towards us; the pulsar may be too faint to be detectable; or there may be an offset in the pulsar position caused by a kick. Aims. Our goal is to find new pulsars in SNRs and explore their possible association with the remnant. The search and selection of the remnants presented in this paper was inspired by the non-detection of any X-ray bright compact objects in these remnants when previously studied. Methods. Five SNRs were searched for radio pulsars with the Green Bank Telescope at 820 MHz with multiple pointings to cover the full spatial extent of the remnants. A periodicity search plus an acceleration search up to 500 m s−2 and a single pulse search were performed for each pointing in order to detect potential isolated binary pulsars and single pulses, respectively. Results. No new pulsars were detected in the survey. However, we were able to re-detect a known pulsar, PSR J2047+5029, near SNR G89.0+4.7. We were unable to detect the radio-quiet gamma-ray pulsar PSR J2021+4026, but we do find a flux density limit of 0.08 mJy. Our flux density limits make our survey two to 16 times more sensitive than previous surveys, while also covering the whole spatial extent of the same remnants. Conclusions. We discuss potential explanations for the non-detection of a pulsar in the studied SNRs and conclude that sensitivity is still the most likely factor responsible for the lack of pulsars in some remnants.

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Somer, A. "New Pulsars from Arecibo Drift Scan Search." International Astronomical Union Colloquium 177 (2000): 17–20. http://dx.doi.org/10.1017/s0252921100058875.

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AbstractWe report the discovery of 3 pulsars, PSR J0030+0451, PSR J0711+09, and PSR J1313+09 that were found in a three dimensional (DM, period, position) search at 430 MHz using the 305m Arecibo telescope. PSR J0030+0451 is a nearby 4.8-millisecond solitary pulsar. Spin and astrometric parameters are presented for the three new pulsars. We have measured significant polarization in the millisecond pulsar, PSR J0030+0451, over more than 50% of the period and use these data and also a morphological decomposition of the profile to briefly discuss magnetospheric models.

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van Leeuwen, Joeri, Klim Mikhailov, Evan Keane, Thijs Coenen, Liam Connor, Vlad Kondratiev, Daniele Michilli, and Sotiris Sanidas. "LOFAR radio search for single and periodic pulses from M 31." Astronomy & Astrophysics 634 (January 28, 2020): A3. http://dx.doi.org/10.1051/0004-6361/201937065.

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Bright short radio bursts are emitted by sources at a wide range of distances: from the nearby Crab pulsar to remote fast radio bursts (FRBs). FRBs are likely to originate from distant neutron stars, but our knowledge of the radio pulsar population has been limited to the Galaxy and the Magellanic Clouds. In an attempt to increase our understanding of extragalactic pulsar populations and their giant-pulse emission, we employed the low-frequency radio telescope LOFAR to search the Andromeda galaxy (M 31) for radio bursts emitted by young Crab-like pulsars. For direct comparison we also present a LOFAR study on the low-frequency giant pulses from the Crab pulsar; their fluence distribution follows a power law with slope 3.04 ± 0.03. A number of candidate signals were detected from M 31, but none proved persistent. FRBs are sometimes thought of as Crab-like pulsars with exceedingly bright giant pulses; based on our sensitivity, we can rule out that M 31 hosts pulsars that are more than an order of magnitude brighter than the Crab pulsar if their pulse scattering follows that of the known FRBs.

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Siemion, Andrew, Matthew Bailes, Geoff Bower, Jayanth Chennamangalam, Jim Cordes, Paul Demorest, Julia Deneva, et al. "A search for pulsars in the central parsecs of the Galactic center." Proceedings of the International Astronomical Union 8, S291 (August 2012): 57. http://dx.doi.org/10.1017/s1743921312023149.

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AbstractThe discovery of a pulsar or pulsars orbiting near the Galactic Center (GC) could offer an unprecedented probe of strong-field gravity, the properties of our galaxy's supermassive black hole and insights into the paradoxical star formation history of the region. However, searching for pulsars near the GC is severely hampered by the large electron densities along our line of sight and the scattering-induced pulse broadening of the pulsar emission observed through it. As the broadened pulse length approaches the pulsar period, the periodicity in pulsar emission becomes nearly undetectable. Searches extended to higher frequencies, in an effort to reduce scattering, suffer from reduced intrinsic flux, higher system temperatures and increased atmospheric opacity. We are currently attempting to mitigate the challenges associated with searching for pulsars near the GC by employing new wide bandwidth receivers, upgraded IF distribution systems and novel digital spectrometers in a GC pulsar search campaign at the Green Bank Telescope in West Virginia, USA.Our search will cover two frequency bands, from 12-15 GHz (Ku Band) and 18-26 GHz (K Band), during a total of approximately 30 hours of observations, with expected characteristic 10-sigma sensitivities between 5-10 micro-Jy. Our first observations are scheduled for mid-March 2012. Here we will present the status of our observations and initial results.

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D’Amico, N., R. N. Manchester, R. N. Manchester, J. M. Durdin, and W. C. Erickson. "A Search of Steep-Spectrum Radio Sources for Millisecond Pulsars." Publications of the Astronomical Society of Australia 6, no. 2 (1985): 174–76. http://dx.doi.org/10.1017/s1323358000018026.

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AbstractA total of 18 radio sources selected on the basis of steep low-frequency radio spectra have been searched for the presence of millisecond pulsars using the Molonglo Observatory synthesis telescope. The search covered pulsar periods down to 2 ms with a limiting sensitivity of approximately 10 mJy. No pulsars were detected.

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Kramer, M., A. Jessner, P. Müller, and R. Wielebinski. "A high frequency search for highly dispersed pulsars." International Astronomical Union Colloquium 160 (1996): 13–14. http://dx.doi.org/10.1017/s0252921100040884.

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The majority of known pulsars have been discovered by pulsar searches at low radio frequencies (v< 1 GHz). However, such searches are subject to various deleterious effects, viz the Galactic background radiation (∝v−2.8), dispersion smearing (∝v−3) and also scatter broadening (∝v−4.4). Dispersion smearing and, in particular, scatter broadening prohibit the detection of pulsars with high dispersion measures at low frequencies (cf. Fig. 1a). This is highlighted by the fact that all 11 known pulsars with DM>600 cm−3pc have been discovered during the only two surveys performed to date above 1 GHz, i.e. at 1.4 GHz by Clifton et al. (1992) and at 1.5 GHz by Johnston et al. (1992). However, scattering is still a limiting factor at even 1.4/1.5 GHz. For example B1750—24 is observed with a double component profile at 4.85 GHz (Kijak et al. 1996), whereas at 1.4 GHz the components are completely smeared out due to scatter broadening (cf. Clifton et al. 1992). Therefore, the galactic population of highly dispersed pulsars is still not known. In order to reveal this hidden sample, we have recently started a search in Effelsberg at 4.85 GHz where limitations due to scattering are essentially not existent (see Fig. 1a). The use of this extraordinary high frequency for pulsar searches enables us to observe with a large bandwidth but a small number of filterbank channels, so that the necessary computer power is radically reduced. However, the general steepness of pulsar spectra demands a highly sensitive observing system, otherwise, only the most luminous sources can be detected. A serious disadvantage of a high frequency search is the small telescope beam requiring a lot of observing time to search even a small area of the sky. A restriction of the search area is therefore highly recommended.

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Perrodin, D., M. Burgay, A. Corongiu, M. Pilia, A. Possenti, M. N. Iacolina, E. Egron, et al. "Pulsar science at the Sardinia Radio Telescope." Proceedings of the International Astronomical Union 13, S337 (September 2017): 392–93. http://dx.doi.org/10.1017/s1743921317009097.

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AbstractThe Sardinia Radio Telescope (SRT) is a modern, fully-steerable 64-m dish located in San Basilio, Sardinia (Italy). It is characterized by an active surface that allows it to cover a wide range of radio frequencies (300 MHz to 100 GHz). During SRT’s commissioning phase, we installed the hardware and software needed for pulsar observations. Since then, SRT has taken part in Large European Array for Pulsars and European Pulsar Timing Array observations for the purpose of gravitational wave detection. We have installed a new S-band receiver that will allow us to search for pulsars in the Galactic Center. We also plan to combine our efforts to search for Extraterrestrial Intelligence (SETI) with the search for pulsars and Fast Radio Bursts.

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Cameron, A. D., D. J. Champion, M. Bailes, V. Balakrishnan, E. D. Barr, C. G. Bassa, S. Bates, et al. "The High Time Resolution Universe Pulsar Survey – XVI. Discovery and timing of 40 pulsars from the southern Galactic plane." Monthly Notices of the Royal Astronomical Society 493, no. 1 (January 14, 2020): 1063–87. http://dx.doi.org/10.1093/mnras/staa039.

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ABSTRACT We present the results of processing an additional 44 per cent of the High Time Resolution Universe South Low Latitude (HTRU-S LowLat) pulsar survey, the most sensitive blind pulsar survey of the southern Galactic plane to date. Our partially coherent segmented acceleration search pipeline is designed to enable the discovery of pulsars in short, highly accelerated orbits, while our 72-min integration lengths will allow us to discover pulsars at the lower end of the pulsar luminosity distribution. We report the discovery of 40 pulsars, including three millisecond pulsar-white dwarf binary systems (PSRs J1537−5312, J1547−5709, and J1618−4624), a black-widow binary system (PSR J1745−23) and a candidate black-widow binary system (PSR J1727−2951), a glitching pulsar (PSR J1706−4434), an eclipsing binary pulsar with a 1.5-yr orbital period (PSR J1653−45), and a pair of long spin-period binary pulsars which display either nulling or intermittent behaviour (PSRs J1812−15 and J1831−04). We show that the total population of 100 pulsars discovered in the HTRU-S LowLat survey to date represents both an older and lower luminosity population, and indicates that we have yet to reach the bottom of the luminosity distribution function. We present evaluations of the performance of our search technique and of the overall yield of the survey, considering the 94 per cent of the survey which we have processed to date. We show that our pulsar yield falls below earlier predictions by approximately 25 per cent (especially in the case of millisecond pulsars), and discuss explanations for this discrepancy as well as future adaptations in RFI mitigation and searching techniques which may address these shortfalls.

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Lazio, T. Joseph W., J. Fischer, and James M. Cordes. "Searches for Pulsar Planetary Systems." Symposium - International Astronomical Union 213 (2004): 101–6. http://dx.doi.org/10.1017/s0074180900193076.

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The first extrasolar planetary system was discovered around the pulsar PSR B1257+12, and the planets therein remain the lowest mass exoplanets known (with one whose mass is of order a lunar mass). Pulsar planetary systems will remain the only extrasolar planetary systems within which terrestrial-mass planets can be detected for the near future, and multiple pulsar planetary systems would provide strong circumstantial evidence that terrestrial-mass planets are ubiquitous, and possibly information about the formation of terrestrial-mass planets. We summarize two searches for planetary or proto-planetary systems around pulsars. The first is a series of infrared observations of millisecond pulsars in which the objective is to detect (proto-planetary) disks. The second uses a genetic algorithm—a function optimization method based on evolutionary processes in the natural world—to search for the signatures of planetary perturbations in pulse timing data.

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Postnov, Konstantin, and Nataliya Porayko. "Search for Ultralight Scalar Dark Matter from Pulsar Timing." Proceedings of the International Astronomical Union 11, A29B (August 2015): 351–53. http://dx.doi.org/10.1017/s1743921316005500.

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AbstractWe perform a Bayesian analysis of pulsar-timing residuals from the NANOGrav pulsar-timing array to search for a specific form of stochastic narrow-band signal produced by oscillating gravitational potential (Gravitational Potential Background) in the Galactic halo. Such oscillations arise in models of warm dark matter composed of an ultralight massive scalar field (m ≃ 10−23 eV). The propagation of an electromagnetic signal from a pulsar through the time-dependent spacetime will leave an imprint in the pulsar timing, much like a gravitational wave. From the physical point of view, this is the classical Sachs-Wolfe effect. A distinctive feature of the pulsar-timing residuals due to GBP produced by a variable scalar field is that the amplitude of the TOA residuals should be independent of the pulsar location in the sky. In the monochromatic approximation, the stringent upper limit (95% C.L.) on the variable gravitational potential amplitude is found to be (Ψc<1.14 × 10−15), corresponding to the characteristic strain hc = 2$\sqrt{3}$Ψc < 4 × 10−15 at f=1.75 × 10−8 Hz. In the narrow-band approximation, the upper limit of this background energy density is ΩGPB < 1.27 × 10−9 at f=1.75 × 10−8 Hz. These limits are an order of magnitude higher than the expected signal amplitude assuming all Galactic dark matter is made of such scalar particles. The applied analysis of the pulsar-timing residuals can be used to search for any narrow-band stochastic signals with different correlation properties. As a by-product, parameters of the red noise present in four NANOGrav pulsars were found.

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Keane, Evan F. "Pulsar Science with the SKA." Proceedings of the International Astronomical Union 13, S337 (September 2017): 158–64. http://dx.doi.org/10.1017/s1743921317009188.

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AbstractThe Square Kilometre Array (SKA) will be sensitive enough to discover all of the pulsars in the Milky Way that are beamed towards Earth. Already in the initial deployment, SKA Phase 1, it will make significant advances in pulsar science. In these proceedings I briefly overview what the SKA is, and describe its pulsar search and timing capabilities.

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Athanasiadis, Tilemachos M., Marina Berezina, John Antoniadis, David J. Champion, Marilyn Cruces, Laura Spitler, and Michael Kramer. "A search for pulsar companions around low-mass white dwarfs." Monthly Notices of the Royal Astronomical Society 505, no. 4 (May 31, 2021): 4981–88. http://dx.doi.org/10.1093/mnras/stab1580.

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ABSTRACT We report on a search for pulsars at the positions of eight low-mass white dwarfs and one higher mass white dwarf with the 100-m Effelsberg Radio Telescope. These systems have orbital parameters suggesting that their unseen companions are either massive white dwarfs or neutron stars (NSs). Our observations were performed at 1.36 GHz, reaching sensitivities of 0.1–0.2 mJy. We searched our data accounting for the possible acceleration and jerk of the pulsar signals due to orbital motion, but found no significant pulsar signals. Considering our result jointly with 20 non-detections of similar systems with the Greenbank Radio Telescope, we infer fNS ≤ 0.10, for the fraction of NSs orbiting these white dwarfs. We discuss the sensitivity of this result to the underlying assumptions and conclude with a brief discussion on the prospects of targeted surveys for discovering millisecond pulsars.

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Straal, S. M., and J. van Leeuwen. "A LOFAR search for steep-spectrum pulsars in supernova remnants and pulsar wind nebulae." Astronomy & Astrophysics 623 (March 2019): A90. http://dx.doi.org/10.1051/0004-6361/201833922.

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Pinpointing a pulsar in its parent supernova remnant (SNR) or resulting pulsar wind nebula (PWN) is key to understanding its formation history and the pulsar wind mechanism, yet only about half the SNRs and PWNe appear associated with a pulsar. Our aim was to find the pulsars in a sample of eight known and new SNRs and PWNe. Using the LOFAR radio telescope at 150 MHz, each source was observed for 3 h. We covered the entire remnants where needed, by employing many tied-array beams to tile out even the largest objects. For objects with a confirmed point source or PWN we constrained our search to those lines of sight. We identified a promising radio pulsar candidate towards PWN G141.2+5.0. The candidate, PSR J0337+61, has a period of 94 ms and a DM of 226 pc cm−3. We re-observed the source twice with increased sensitivities of 30% and 50%, but did not re-detect it. It thus remains unconfirmed. For our other sources we obtain very stringent upper limits of 0.8 − 3.1 mJy at 150 MHz. Generally, we can rule out that the pulsars travelled out of the remnant. From these strict limits we conclude our non-detections towards point sources and PWNe are the result of beaming and propagation effects. Some of the remaining SNRs should host a black hole rather than a neutron star.

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Bruel, P. "Extending the event-weighted pulsation search to very faint gamma-ray sources." Astronomy & Astrophysics 622 (February 2019): A108. http://dx.doi.org/10.1051/0004-6361/201834555.

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Context. Because of the relatively broad angular resolution of current gamma-ray instruments in the MeV–GeV energy range, the photons of a given source are mixed with those coming from nearby sources or diffuse background. This source confusion seriously hampers the search for pulsation from faint sources. Aims. Statistical tests for pulsation can be made significantly more sensitive when the probability that a photon comes from the pulsar is used as a weight. However, computing this probability requires knowledge of the spectral model of all sources in the region of interest, including the pulsar itself. This is not possible for very faint pulsars that are not detected as gamma-ray sources or whose spectrum is not measured precisely enough. Extending the event-weighted pulsation search to such very faint gamma-ray sources would allow improving our knowledge of the gamma-ray pulsar population. Methods. We present two methods that overcome this limitation by scanning the spectral parameter space, while minimizing the number of trials. The first one approximates the source to background ratio yielding a simple estimate of the weight while the second one makes use of the full spatial and spectral information of the region of interest around the pulsar. Results. We tested these new methods on a sample of 144 gamma-ray pulsars already detected by the Fermi Large Area Telescope data. Both methods detect pulsation from all pulsars of the sample, including the ones for which no significant phase-averaged gamma-ray emission is detected.

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Fauci, F., M. Guainazzi, and V. Boriakoff. "Pulsar search in M33." Il Nuovo Cimento C 16, no. 6 (November 1993): 783–88. http://dx.doi.org/10.1007/bf02507877.

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Wang, Jingbo, G. Hobbs, and Na Wang. "Search for the gravitational wave memory effect with the Parkes Pulsar Timing Array." Proceedings of the International Astronomical Union 8, S291 (August 2012): 543–45. http://dx.doi.org/10.1017/s1743921312024817.

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AbstractGravitational wave bursts produced by supermassive binary black hole mergers will leave a persistent imprint on the space-time metric. Such gravitational wave memory signals are detectable by pulsar timing arrays as a glitch event that would seem to occur simultaneously for all pulsars. In this paper, we describe an initial algorithm which can be used to search for gravitational wave memory signals. We apply this algorithm to the Parkes Pulsar Timing Array data set. No significant gravitational wave memory signal is founded in the data set.

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Potapov, Vladimir A., and Sergei M. Kopeikin. "Timing of binary pulsars and the search for the low-frequency gravitational waves." Proceedings of the International Astronomical Union 5, H15 (November 2009): 234. http://dx.doi.org/10.1017/s1743921310008999.

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AbstractMillisecond and binary pulsars are the most stable natural standards of astronomical time giving us a unique opportunity to search for gravitational waves (GW) and to test General Relativity. GWs from violent events in early Universe and from the ensemble of galactic and extragalactic objects perturb propagation of radio pulses from a pulsar to observer bringing about stochastic fluctuations in the times of arrival of the pulses (TOA). If one observes the pulsar over a sufficiently long time span, the fluctuations will be registered as a low-frequency, correlated noise affecting the timing residuals in the frequency range 10−12 ÷ 10−7 Hz. This work demonstrates how the standard procedure of processing of the pulsar timing data can bias the estimate of the upper limit on the density of the GW background (GWB).

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Mcconnell, D., P. M. Mcculloch, P. A. Hamilton, J. G. Ables, P. J. Hall, C. E. Jacka, and A. J. Hunt. "Radio pulsars in the Magellanic Clouds." Symposium - International Astronomical Union 148 (1991): 322. http://dx.doi.org/10.1017/s0074180900200661.

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The Large Magellanic Cloud (LMC) and Small Magellanic Cloud (SMC) have been searched for radio pulsars using the 64-m Parkes radiotelescope. The search has resulted in the discovery of four pulsars. Observed dispersion measures to each suggest that three lie in the Clouds (two in the LMC, one in the SMC) and that the fourth, which was found in the direction of the LMC, is a foreground object belonging to the galactic pulsar population.

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Carramiñana, Alberto, Andrej Čadež, and César Alvarez. "CLYPOS: the Cananea-Ljubljana Young Pulsar Optical Survey." International Astronomical Union Colloquium 177 (2000): 295–96. http://dx.doi.org/10.1017/s0252921100059777.

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AbstractThe Cananea-Ljubljana Young Pulsar Optical Survey, or CLYPOS, is an observational study of ≳ 30 known radio pulsars, in search for pulsed optical emission. The survey is being carried out at the 2.12m telescope of the Observatorio Astrofísico Guillermo Haro, near Cananea, Sonora, using the stroboscopic camera of the University of Ljubljana. We restricted the study to young pulsars with declinationδ> −35°, prioritized in terms ofE/d2. Our strategy consists in spending two hours of observing time per pulsar, scanning the whole pulsed-phase interval three times. Further details are given below.

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Parent, E., V. M. Kaspi, S. M. Ransom, C. Patel, and M. Krasteva. "The implementation of a Fast-Folding Algorithm in the PALFA survey." Proceedings of the International Astronomical Union 13, S337 (September 2017): 388–89. http://dx.doi.org/10.1017/s1743921317008638.

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AbstractThe PALFA survey, the most sensitive blind search for radio pulsars, has now discovered 180 pulsars in the Galactic Plane, the vast of which have periods shorter than 2 seconds. One reason that pulsar surveys may miss long-period radio pulsars is the strong effect of red noise at low modulation frequencies. It is possible to address this reduction in sensitivity by using a Fast-Folding Algorithm (FFA). We have adapted this algorithm for radio pulsar searching and applied it to PALFA observations. A sensitivity analysis of the algorithm has been conducted using synthetic pulsar signals injected in real observational data and this study shows that the FFA improves the PALFA survey sensitivity, as reported in Lazarus et al.(2015), by at least a factor of two at periods of ~6 sec, implying that the PALFA survey should discover more long-period radio pulsars in the future.

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Eatough, R. P., P. Torne, G. Desvignes, M. Kramer, R. Karuppusamy, B. Klein, L. G. Spitler, et al. "Multi-epoch searches for relativistic binary pulsars and fast transients in the Galactic Centre." Monthly Notices of the Royal Astronomical Society 507, no. 4 (August 17, 2021): 5053–68. http://dx.doi.org/10.1093/mnras/stab2344.

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ABSTRACT The high stellar density in the central parsecs around the Galactic Centre makes it a seemingly favourable environment for finding relativistic binary pulsars. These include pulsars orbiting other neutron stars, stellar-mass black holes, or the central supermassive black hole, Sagittarius A*. Here, we present multi-epoch pulsar searches of the Galactic Centre at four observing frequencies, $4.85,\, 8.35,\, 14.6,\, 18.95\, {\rm GHz}$, using the Effelsberg 100-m radio telescope. Observations were conducted 1 yr prior to the discovery of, and during monitoring observations of, the Galactic Centre magnetar PSR J1745−2900. Our data analysis features acceleration searches on progressively shorter time series to maintain sensitivity to relativistic binary pulsars. The multi-epoch observations increase the likelihood of discovering transient or nulling pulsars, or ensure orbital phases are observed at which acceleration search methods work optimally. In ${\sim}147\, {\rm h}$ of separate observations, no previously undiscovered pulsars have been detected. Through calibration observations, we conclude this might be due to insufficient instantaneous sensitivity, caused by the intense continuum emission from the Galactic Centre, its large distance, and, at higher frequencies, the aggregate effect of steep pulsar spectral indices and atmospheric contributions to the system temperature. Additionally, we find that for millisecond pulsars in wide circular orbits $({\lesssim}800\, {\rm d})$ around Sagittarius A*, linear acceleration effects cannot be fully corrected in deep observations $(9\, {\rm h})$ with existing software tools. Pulsar searches of the Galactic Centre with the next generation of radio telescopes – such as MeerKat, ngVLA, and SKA1-mid – will have improved chances of uncovering this elusive population.

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Cordes, James. "Optimizing Pulsar Searches Against Propagation Effects." International Astronomical Union Colloquium 182 (2001): 47–52. http://dx.doi.org/10.1017/s0252921100000671.

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AbstractPropagation effects are well known to limit the sensitivity of pulsar searches based on periodicity detections. I define several regimes for pulsar searches that are based on whether the search sensitivity is luminosity limited, dispersion limited or scattering limited. Consideration of these regimes allows general statements to be made about pulsar searches in and out of the Galactic plane. Telescope size matters, but only to a point. Once scattering becomes important it is better to search more sky (in a blind survey) than to integrate longer on a given sky position. Example surveys are described.

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Wagner, Stefan J., and W. Seifert. "Optical Polarization Measurements of Pulsars." International Astronomical Union Colloquium 177 (2000): 315–18. http://dx.doi.org/10.1017/s0252921100059868.

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AbstractWe investigate the polarization characteristics of optical emission from young pulsars. In a first attempt we search for polarization in images without time resolution in order to select suitable candidates for time-resolved studies. Polarization information constrains the nature of the faint optical emission of pulsars and will eventually allow to derive the topology of the field in those areas were optical radiation is emitted. We determine the polarization of the time-integrated optical emission of the SMC pulsar B0540-69 and the Vela pulsar B0833-45. We identify a new candidate optical counterpart for the young pulsar B1509-58 and find that the old candidate is unpolarized. The polarization of these three sources is rather high in view of the assumption that averaging over a putative swing of the polarization angle through 180 degrees will lead to depolarisation in the pulse-averaged signal.We also detect high degrees of polarization in the synchrotron nebula surrounding the LMC pulsar B0540-69, indicating even further similarity to the Crab.

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Lynch, Ryan S. "The Green Bank North Celestial Cap Pulsar Survey: Status and Future." Proceedings of the International Astronomical Union 13, S337 (September 2017): 13–16. http://dx.doi.org/10.1017/s174392131700953x.

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AbstractThe ongoing Green Bank North Celestial Cap pulsar survey is using the Green Bank Telescope to search for pulsars and transients over 85% of the celestial sphere. The survey has resulted in over 150 new pulsars, among which are high-precision millisecond pulsars, several binary pulsars, including at least one relativistic double neutron star system, nulling pulsars, and several nearby millisecond pulsars. We find no fast radio bursts in the survey to date. We present these results and discuss the future prospects for the survey.

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Clark, Colin J., Jason Wu, Holger J. Pletsch, and Lucas Guillemot. "The Einstein@Home Survey for Gamma-ray Pulsars." Proceedings of the International Astronomical Union 13, S337 (September 2017): 21–24. http://dx.doi.org/10.1017/s1743921317009231.

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AbstractSince the launch of the Fermi Gamma-ray Space Telescope in 2008, the onboard Large Area Telescope (LAT) has detected gamma-ray pulsations from more than 200 pulsars. A large fraction of these remain undetected in radio observations, and could only be found by directly searching the LAT data for pulsations. However, the sensitivity of such “blind” searches is limited by the sparse photon data and vast computational requirements. In this contribution we present the latest large-scale blind-search survey for gamma-ray pulsars, which ran on the distributed volunteer computing system, Einstein@Home, and discovered 19 new gamma-ray pulsars. We explain how recent improvements to search techniques and LAT data reconstruction have boosted the sensitivity of blind searches, and present highlights from the survey’s discoveries. These include: two glitching pulsars; the youngest known radio-quiet gamma-ray pulsar; and two isolated millisecond pulsars (MSPs), one of which is the only known radio-quiet rotationally powered MSP.

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Morello, V., E. D. Barr, B. W. Stappers, E. F. Keane, and A. G. Lyne. "Optimal periodicity searching: revisiting the fast folding algorithm for large-scale pulsar surveys." Monthly Notices of the Royal Astronomical Society 497, no. 4 (August 6, 2020): 4654–71. http://dx.doi.org/10.1093/mnras/staa2291.

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ABSTRACT The fast folding algorithm (FFA) is a phase-coherent search technique for periodic signals. It has rarely been used in radio pulsar searches, having been historically supplanted by the less computationally expensive fast fourier transform (FFT) with incoherent harmonic summing (IHS). Here, we derive from first principles that an FFA search closely approaches the theoretical optimum sensitivity to all periodic signals; it is analytically shown to be significantly more sensitive than the standard FFT+IHS method, regardless of pulse period and duty cycle. A portion of the pulsar phase space has thus been systematically underexplored for decades; pulsar surveys aiming to fully sample the pulsar population should include an FFA search as part of their data analysis. We have developed an FFA software package, riptide, fast enough to process radio observations on a large scale; riptide has already discovered sources undetectable using existing FFT+IHS implementations. Our sensitivity comparison between search techniques also shows that a more realistic radiometer equation is needed, which includes an additional term: the search efficiency. We derive the theoretical efficiencies of both the FFA and the FFT+IHS methods and discuss how excluding this term has consequences for pulsar population synthesis studies.

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Kopeikin, Sergei. "Stability of pulsar rotational and orbital periods." Proceedings of the International Astronomical Union 5, H15 (November 2009): 226–27. http://dx.doi.org/10.1017/s1743921310008938.

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AbstractMillisecond and binary pulsars are the most stable astronomical standards of frequency. They can be applied to solving a number of problems in astronomy and time-keeping metrology including the search for a stochastic gravitational wave background in the early universe, testing general relativity, and establishing a new time-scale. The full exploration of pulsar properties requires that proper unbiased estimates of spin and orbital parameters of the pulsar be obtained. These estimates depend essentially on the random noise components present in pulsar timing residuals. The instrumental white noise has predictable statistical properties and makes no harm for interpretation of timing observations, while the astrophysical/geophyeical low-frequency noise corrupts them, thus, reducing the quality of tests of general relativity and decreasing the stability of the pulsar time scale.

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Jacoby, B. A. "A Search for Radio Pulsars at High Galactic Latitude." Symposium - International Astronomical Union 218 (2004): 129–30. http://dx.doi.org/10.1017/s0074180900180775.

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We have completed a search for radio pulsars using the Parkes 64 m telescope, covering ∼4500 deg2 between 15° and 30° from the Galactic plane. Each pointing was observed for 265 s with the 13-beam multibeam system at a frequency of 1374 MHz. The signal from each beam was processed by a 96-channel filterbank and sampled every 125 μs, with a bandwidth of 288 MHz. This strategy affords rapid sky coverage and good sensitivity to pulsars with periods as short as 1 ms, whose existence would constrain the neutron star equation of state. Data were analyzed using the workstation cluster at the Swinburne Centre for Astrophysics and Supercomputing. This effort has yielded 26 new pulsars, including seven recycled pulsars. Taken together with the previous Swinburne Intermediate Latitude Pulsar Survey, a total of 95 new pulsars were found over nearly 7500 deg2 of sky between 5° and 30° from the plane of the Galaxy. This large sample of newly discovered objects contains no young pulsars.

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Pshirkov, Maxim S. "Search for ultra-long gravitational waves in pulsars' rotational parameters." Proceedings of the International Astronomical Union 5, H15 (November 2009): 231. http://dx.doi.org/10.1017/s1743921310008963.

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AbstractA method is suggested to explore the gravitational wave background (GWB) in the frequency range from 10−12 to 10−8 Hz. That method is based on the precise measurements of pulsars' rotational parameters: the influence of the gravitational waves (GW) in the range will affect them and therefore some conclusions about energy density of the GWB can be made using analysis of the derivatives of pulsars' rotational frequency. The calculated values of the second derivative from a number of pulsars limit the density of GWB Ωgw as follows: Ωgwh2 < 10−6. Also, the time series of the frequency ν of different pulsars in pulsar array can be cross-correlated pairwise in the same manner as in anomalous residuals analysis thus providing the possibility of GWB detection in ultra-low frequency range.

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Krishnamohan, S., D. K. Mohanty, A. R. Patnaik, and T. Velusamy. "Search for Plerions in the Direction of Two Young Pulsars." Symposium - International Astronomical Union 125 (1987): 124. http://dx.doi.org/10.1017/s0074180900160590.

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Two of the recently discovered pulsars PSR 1800-21 and 1823-13 have characteristics ages of 17,000 and 22,000 yr respectively and all the three known pulsars that are younger than these two lie within the known supernova remnants (Clifton and Lyne, 1986). These two pulsars are expected to have, by scaling from the Crab nebula, plerions of ∼1 Jy each associated with them at 327 MHz. We mapped a field of 1.˚95 × 1.˚5 around both the pulsars with the Ooty Synthesis Radio Telescope (Swarup, 1984). As the fields are on the galactic plane having complex large scale emission and as the plerions are expected to be compact, we have made maps by excluding baselines less than 500 λ. This would make our maps insensitive to emission regions larger than ∼7 arc min. The synthesised beam is 96 × 36 arc sec in PA 0°. No source with a surface brightness greater than 60 mJy/beam was detected in the direction of PSR 1823-13. An unresolved source of ∼150 mJy was detected, in the positional error box of PSR 1800-21, as is shown in the figure. No pulsed emission with an average flux density greater than 10 mJy was detected from this continuum source. It is possible that the pulse is so highly scatter broadened that it becomes undetectable at 327 MHz and the detected source is the scatter broadened pulsar. But, such a possibility seems unlikely as the pulsar's dispersion measure is only 230 cm−3 pc, leaving the interesting possibility that the detected source is a plerion associated with the pulsar.

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Caballero, R. N. "Solar-System Studies with Pulsar Timing Arrays." Proceedings of the International Astronomical Union 13, S337 (September 2017): 154–57. http://dx.doi.org/10.1017/s1743921317009905.

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AbstractHigh-precision pulsar timing is central to a wide range of astrophysics and fundamental physics applications. When timing an ensemble of millisecond pulsars in different sky positions, known as a pulsar timing array (PTA), one can search for ultra-low-frequency gravitational waves (GWs) through the spatial correlations that spacetime deformations by passing GWs are predicted to induce on the pulses’ times-of-arrival (TOAs). A pulsar-timing model, requires the use of a solar-system ephemeris (SSE) to properly predict the position of the solar-system barycentre, the (quasi-)inertial frame where all TOAs are referred. Here, I discuss how while errors in SSEs can introduce correlations in the TOAs that may interfere with GW searches, one can make use of PTAs to study the solar system. I discuss work done within the context of the European Pulsar Timing Array and the International Pulsar Timing Array collaborations. These include new updates on the masses of planets from PTA data, first limits on masses of the most massive asteroids, and comparisons between SSEs from independent groups. Finally, I discuss a new approach in setting limits on the masses of unknown bodies in the solar system and calculate mass sensitivity curves for PTA data.

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Barkov, Maxim V., and Maxim Lyutikov. "On the nature of radio filaments near the Galactic Centre." Monthly Notices of the Royal Astronomical Society: Letters 489, no. 1 (August 8, 2019): L28—L31. http://dx.doi.org/10.1093/mnrasl/slz124.

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ABSTRACT We suggest that narrow, long radio filaments near the Galactic Centre arise as kinetic jets – streams of high-energy particles escaping from ram pressure confined pulsar wind nebulae (PWNe). The reconnection between the PWN and interstellar magnetic field allows pulsar wind particles to escape, creating long narrow features. They are the low-frequency analogues of kinetic jets seen around some fast-moving pulsars, such as The Guitar and The Lighthouse PWNe. The radio filaments trace a population of pulsars also responsible for the Fermi GeV excess produced by the Inverse Compton scattering by the pulsar wind particles. The magnetic flux tubes are stretched radially by the large-scale Galactic winds. In addition to PWNe accelerated particles can be injected at supernovae remnants. The model predicts variations of the structure of the largest filaments on scales of ∼dozens of years – smaller variations can occur on shorter time-scales. We also encourage targeted observations of the brightest sections of the filaments and of the related unresolved point sources in search of the powering PWNe and pulsars.

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Stappers, B. W., B. M. Gaensler, and S. Johnston. "A deep search for pulsar wind nebulae using pulsar gating." Monthly Notices of the Royal Astronomical Society 308, no. 3 (September 23, 1999): 609–17. http://dx.doi.org/10.1046/j.1365-8711.1999.02701.x.

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Ackermann, M., M. Ajello, L. Baldini, J. Ballet, G. Barbiellini, D. Bastieri, K. Bechtol, et al. "FERMI-LAT SEARCH FOR PULSAR WIND NEBULAE AROUND GAMMA-RAY PULSARS." Astrophysical Journal 726, no. 1 (December 13, 2010): 35. http://dx.doi.org/10.1088/0004-637x/726/1/35.

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Rosen, R., J. Swiggum, M. A. McLaughlin, D. R. Lorimer, M. Yun, S. A. Heatherly, J. Boyles, et al. "THE PULSAR SEARCH COLLABORATORY: DISCOVERY AND TIMING OF FIVE NEW PULSARS." Astrophysical Journal 768, no. 1 (April 17, 2013): 85. http://dx.doi.org/10.1088/0004-637x/768/1/85.

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Guillemot, L., F. Octau, I. Cognard, G. Desvignes, P. C. C. Freire, D. A. Smith, G. Theureau, and T. H. Burnett. "Timing of PSR J2055+3829, an eclipsing black widow pulsar discovered with the Nançay Radio Telescope." Astronomy & Astrophysics 629 (September 2019): A92. http://dx.doi.org/10.1051/0004-6361/201936015.

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We report on the timing observations of the millisecond pulsar PSR J2055+3829 originally discovered as part of the SPAN512 survey conducted with the Nançay Radio Telescope. The pulsar has a rotational period of 2.089 ms and is in a tight 3.1 h orbit around a very low mass (0.023 ≤ mc ≲ 0.053 M⊙, 90% c.l.) companion. Our 1.4 GHz observations reveal the presence of eclipses of the radio signal of the pulsar, caused by the outflow of material from the companion, for a few minutes around superior conjunction of the pulsar. The very low companion mass, the observation of radio eclipses, and the detection of time variations of the orbital period establish PSR J2055+3829 as a “black widow” (BW) pulsar. Inspection of the radio signal from the pulsar during ingress and egress phases shows that the eclipses in PSR J2055+3829 are asymmetric and variable, as is commonly observed in other similar systems. More generally, the orbital properties of the new pulsar are found to be very similar to those of other known eclipsing BW pulsars. No gamma-ray source has been detected at the location of the pulsar in recent Fermi-LAT source catalogs. We used the timing ephemeris to search ten years of Fermi Large Area Telescope (LAT) data for gamma-ray pulsations, but were unable to detect any. This non-detection could be a consequence of the large distance of the pulsar compared to those of known gamma-ray millisecond pulsars outside of globular clusters. We finally compared the mass functions of eclipsing and non-eclipsing BW pulsars and confirmed previous findings that eclipsing BWs have higher mass functions than their non-eclipsing counterparts. Larger inclinations could explain the higher mass functions of eclipsing BWs. On the other hand, the mass function distributions of Galactic disk and globular cluster BWs appear to be consistent, suggesting, despite the very different environments, the existence of common mechanisms taking place in the last stages of evolution of BWs.

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Oostrum, L. C., J. van Leeuwen, Y. Maan, T. Coenen, and C. H. Ishwara-Chandra. "A search for pulsars in subdwarf B binary systems and discovery of giant-pulse emitting PSR J0533−4524." Monthly Notices of the Royal Astronomical Society 492, no. 4 (January 16, 2020): 4825–36. http://dx.doi.org/10.1093/mnras/staa146.

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ABSTRACT Binary millisecond pulsars (MSPs) provide several opportunities for research of fundamental physics. However, finding them can be challenging. Several subdwarf B (sdB) binary systems with possible neutron star companions have been identified, allowing us to perform a targeted search for MSPs within these systems. Six sdBs with companions in the neutron star mass range, as determined from their optical light curves, were observed with the Green Bank and Westerbork radio telescopes. The data were searched for periodic signals as well as single pulses. No radio pulsations from sdB systems were detected, down to an average sensitivity limit of $0.11\,$mJy. We did, however, discover a pulsar in the field of sdB HE0532−4503. Follow-up observations with the Giant Metrewave Radio Telescope showed that this pulsar, J0533−4524, is not spatially coincident with the sdB system. The pulsar has a relatively low magnetic field but still emits giant pulses. We place an upper limit of three to the number of radio pulsars in the six sdB systems. The non-detections may be explained by a combination of the MSP beaming fraction, luminosity, and a recycling fraction <0.5. Alternatively, the assumption of corotation between the MSP and sdB may break down, which implies the systems are more edge-on than previously thought. This would shift the predicted companion masses into the white dwarf range. It would also explain the relative lack of edge-on sdB systems with massive companions.

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Camilo, F. "Intermediate-Mass Binary Pulsars: a New Class of Objects?" International Astronomical Union Colloquium 160 (1996): 539–40. http://dx.doi.org/10.1017/s0252921100042330.

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Approximately 4/5 of the ∼ 35 millisecond pulsars known in the disk of the Galaxy are in binary systems. The vast majority of these binary pulsars have (presumed) helium white dwarf companions with massesm2< 0.45 M⊙, spin periodsP< 10 ms, and all are in extremely circular orbits (Fig. 1). In a search for millisecond pulsars with the Arecibo radio telescope, we have recently discovered PSR J1022+1001, a 16.45 ms pulsar in a 7.8 d orbit with a companion that is at least 0.73 M⊙, and is more likely as massive as 0.8−1.0M⊙; and PSR J0621+1002, a 28.85 ms pulsar in an 8.3 d orbit with a companion at least 0.45 M⊙, and more likely withm2≈ 0.54 M⊙. One other system, PSR J2145–0750, hasP= 16.05 ms, orbital periodPb= 6.8 d, andm2≈ 0.50 M⊙(see Table 1).

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Zhang, Hailong, Markus Demleitner, Jie Wang, Na Wang, Jun Nie, and Jianping Yuan. "The XinJiang Astronomical Observatory NSRT Pulsar Data Archive." Advances in Astronomy 2019 (January 23, 2019): 1–6. http://dx.doi.org/10.1155/2019/5712682.

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The sensitivity of our pulsar observation system with typical integration time of 16 minutes has reached 0.4 mJy after we have upgraded the receiver cooling system of NanShan 25-m radio telescope (NSRT) at Xinjiang Astronomical Observatory (XAO) in 2002. About 280 pulsars were observed after the upgrade. The NanShan station pulsar data is transmitted to the data center at XAO headquarters via a 300Mb/s dedicated data link for long-term storage, and the remote backup is realized by synchronous data transmission between NanShan station and XAO headquarters. Metadata extraction, archiving, and releasing are completed by the data release servers which are located in XAO headquarters. At present, more than 84000 pulsar observation data files in the PSRFITS format have been released with a maximum file size of 1GB. XAO pulsar data online service provides cone search and multiobject constraint query. We have published our data based on Virtual Observatory (VO) standards. The online pulsar data service is registered in the International Virtual Observatory Alliance’s Registry. Users can access the data through common VO tools.

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Weisberg, J. M., J. J. Morgan, J. T. Despotes, J. E. Everett, and J. M. Cordes. "A Search for Variable Interstellar Magnetic Fields and Neutron Star Precession in Four Years of Polarization Position Angle Measurements on 98 Pulsars." International Astronomical Union Colloquium 177 (2000): 269–70. http://dx.doi.org/10.1017/s0252921100059686.

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AbstractWe have studied the temporal behavior of linearly polarized position angle in a sample of 98 pulsars observed from Arecibo over a four–year period in a search for free precession and changes in interstellar magnetic fields along pulsar– earth lines of sight. We set upper limits on changes in position angle.

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Ray, Paul S., Zaven Arzoumanian, and Keith C. Gendreau. "Searching for X-ray Pulsations from Neutron Stars Using NICER." Proceedings of the International Astronomical Union 13, S337 (September 2017): 187–90. http://dx.doi.org/10.1017/s1743921317008237.

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AbstractThe Neutron Star Interior Composition Explorer (NICER) presents an exciting new capability for exploring the modulation properties of X-ray emitting neutron stars, including large area, low background, extremely precise absolute event time stamps, superb low-energy response and flexible scheduling. The Pulsation Searches and Multiwavelength Coordination working group has designed a 2.5 Ms observing program to search for emission and characterize the modulation properties of about 30 known or suspected neutron star sources across a number of source categories. A key early goal will be to search for pulsations from millisecond pulsars that might exhibit thermal pulsations from the surface suitable for pulse profile modeling to constrain the neutron star equation of state. In addition, we will search for pulsations from transitional millisecond pulsars, isolated neutron stars, low-mass X-ray binaries (LMXBs), accretion-powered millisecond pulsars, central compact objects and other sources. We present our science plan and initial results from the first months of the NICER mission, including the discovery of pulsations from the millisecond pulsar J1231–1411.

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Williamson, Kathryn, Maura McLaughlin, John Stewart, Duncan Lorimer, Harsha Blumer, Cabot Zabriskie, Sue Ann Heatherly, and Ryan Lynch. "The Pulsar Search Collaboratory: Expanding Nationwide." Physics Teacher 57, no. 3 (March 2019): 156–58. http://dx.doi.org/10.1119/1.5092473.

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Titus, N., B. W. Stappers, V. Morello, M. Caleb, M. D. Filipović, V. A. McBride, W. C. G. Ho, and D. A. H. Buckley. "Targeted search for young radio pulsars in the SMC: discovery of two new pulsars." Monthly Notices of the Royal Astronomical Society 487, no. 3 (June 10, 2019): 4332–42. http://dx.doi.org/10.1093/mnras/stz1578.

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ABSTRACT We report the first rotation powered pulsars discovered in the Small Magellanic Cloud (SMC) in more than a decade. PSR J0043–73 and PSR J0052–72 were discovered during a Parkes Multi-Beam (PMB) survey of MCSNR J0127–7332, and five new, optically selected, supernova remnant (SNR) candidates identified by the XMM–Newton survey. In addition to the candidates, we adjusted the PMB rotation to include additional nine SNRs and pulsar wind nebulae. We searched for young pulsars (1–200 ms) employing a Fourier analysis with PRESTO, as well as a search for longer period pulsars (200 ms–360 s) with a fast folding algorithm. Our targeted survey had a limiting flux density of 0.039 mJy for periods greater than 50 ms. Although not the main target of this search it was also sensitive to millisecond pulsars. PSR J0043–73 has a period and dispersion measure of 937.429 37 (26) ms and 115.1 (3.4) pc cm−3, respectively, and PSR J0052–72 has a period of 191.444 328 (46) ms and a DM of 158.6 (1.6) pc cm−3.

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Hobbs, G., L. Guo, R. N. Caballero, W. Coles, K. J. Lee, R. N. Manchester, D. J. Reardon, et al. "A pulsar-based time-scale from the International Pulsar Timing Array." Monthly Notices of the Royal Astronomical Society 491, no. 4 (November 4, 2019): 5951–65. http://dx.doi.org/10.1093/mnras/stz3071.

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ABSTRACT We have constructed a new time-scale, TT(IPTA16), based on observations of radio pulsars presented in the first data release from the International Pulsar Timing Array (IPTA). We used two analysis techniques with independent estimates of the noise models for the pulsar observations and different algorithms for obtaining the pulsar time-scale. The two analyses agree within the estimated uncertainties and both agree with TT(BIPM17), a post-corrected time-scale produced by the Bureau International des Poids et Mesures (BIPM). We show that both methods could detect significant errors in TT(BIPM17) if they were present. We estimate the stability of the atomic clocks from which TT(BIPM17) is derived using observations of four rubidium fountain clocks at the US Naval Observatory. Comparing the power spectrum of TT(IPTA16) with that of these fountain clocks suggests that pulsar-based time-scales are unlikely to contribute to the stability of the best time-scales over the next decade, but they will remain a valuable independent check on atomic time-scales. We also find that the stability of the pulsar-based time-scale is likely to be limited by our knowledge of solar-system dynamics, and that errors in TT(BIPM17) will not be a limiting factor for the primary goal of the IPTA, which is to search for the signatures of nano-Hertz gravitational waves.

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Goncharov, Boris, Xing-Jiang Zhu, and Eric Thrane. "Is there a spectral turnover in the spin noise of millisecond pulsars?" Monthly Notices of the Royal Astronomical Society 497, no. 3 (August 10, 2020): 3264–72. http://dx.doi.org/10.1093/mnras/staa2081.

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ABSTRACT Pulsar timing arrays provide a unique means to detect nanohertz gravitational waves through long-term measurements of pulse arrival times from an ensemble of millisecond pulsars. After years of observations, some timing array pulsars have been shown to be dominated by low-frequency red noise, including spin noise that might be associated with pulsar rotational irregularities. The power spectral density of pulsar timing red noise is usually modelled with a power law or a power law with a turnover frequency below which the noise power spectrum plateaus. If there is a turnover in the spin noise of millisecond pulsars, residing within the observation band of current and/or future pulsar timing measurements, it may be easier than projected to resolve the gravitational-wave background from supermassive binary black holes. Additionally, the spectral turnover can provide valuable insights on neutron star physics. In the recent study by Melatos and Link, the authors provided a derivation of the model for power spectral density of spin noise from superfluid turbulence in the core of a neutron star, from first principles. The model features a spectral turnover, which depends on the dynamical response time of the superfluid and the steady-state angular velocity lag between the crust and the core of the star. In this work, we search for a spectral turnover in spin noise using the first data release of the International Pulsar Timing Array. Through Bayesian model selection, we find no evidence of a spectral turnover. Our analysis also shows that data from PSRs J1939+2134, J1024–0719, and J1713+0747 prefers the power-law model to the superfluid turbulence model.

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Rammala, Isabella, Aris Karastergiou, and Griffin Foster. "Broadband observations of pulsar profiles and frequency dependent DMs." Proceedings of the International Astronomical Union 13, S337 (September 2017): 400–401. http://dx.doi.org/10.1017/s1743921317010353.

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AbstractThe aim of our project is to search for ways to best extract information on pulsar profiles and the interstellar medium (ISM), using the wide frequency bands that are typical of radio telescopes today. Pulsar profiles typically show a strong dependence on frequency. This depends both on the intrinsic radio emission mechanism, and the interaction of the radio waves with the ISM that lies between the pulsars and our detectors on Earth, due mostly to the effects of dispersion and scattering. In this work, we make use of radio pulsar beam models from the existing literature, to generate simulated pulse profiles, observed across various bands (centre frequencies and bandwidths), for each beam model. For all the chosen geometric parameters of the pulsar beam, observed in any frequency band, the simulated profiles manifest a relative shift in phase in their observed components, as a result of the intrinsic profile evolution. This relative shift in phase could be interpreted as an additional component to the ISM induced dispersion measure (DM). This additional DM component due to profile evolution is frequency dependent. We discuss the systematics introduced to pulsar data due to this effect.

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Journal articles on the topic 'Pulsar Search'

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