PulsarX: a new pulsar searching package -I. A high performance folding program for pulsar surveys

Pulsar surveys with modern radio telescopes are becoming increasingly computationally demanding. This is particularly true for wide field-of-view pulsar surveys with radio interferometers, and those conducted in real or quasi-real time. These demands result in data analysis bottlenecks that can limit the parameter space covered by the surveys and diminish their scientific return. In this paper, we address the computational challenge of `candidate folding' in pulsar searching, presenting a novel, efficient approach designed to optimise the simultaneous folding of large numbers of pulsar candidates. We provide a complete folding pipeline appropriate for large-scale pulsar surveys including radio frequency interference (RFI) mitigation, dedispersion, folding and parameter optimization. By leveraging the Fast Discrete Dispersion Measure Transform (FDMT) algorithm proposed by Zackay et al. (2017), we have developed an optimized, and cache-friendly implementation that we term the pruned FDMT (pFDMT). The pFDMT approach efficiently reuses intermediate processing results and prunes the unused computation paths, resulting in a significant reduction in arithmetic operations. In addition, we propose a novel folding algorithm based on the Tikhonov-regularised least squares method (TLSM) that can improve the time resolution of the pulsar profile. We present the performance of its real-world application as an integral part of two major pulsar search projects conducted with the MeerKAT telescope: the MPIfR-MeerKAT Galactic Plane Survey (MMGPS) and the Transients and Pulsars with MeerKAT (TRAPUM) project. In our processing, for approximately 500 candidates, the theoretical number of dedispersion operations can be reduced by a factor of around 50 when compared to brute-force dedispersion, which scales with the number of candidates.Comment: Accepted for publication in A&

Precision timing of PSR J1012+5307 and strong-field GR tests

We report on the high precision timing analysis of the pulsar-white dwarf binary PSR J1012+5307. Using 15 years of multi-telescope data from the European Pulsar Timing Array (EPTA) network, a significant measurement of the variation of the orbital period is obtained. Using this ideal strong-field gravity laboratory we derive theory independent limits for both the dipole radiation and the variation of the gravitational constant.Comment: 3 pages, Proceedings of the 12th Marcel Grossmann Meeting on General Relativity (MG 12

Radio emission from a pulsar’s magnetic pole revealed by general relativity

International audienceBinary pulsars are affected by general relativity (GR), causing the spin axis of each pulsar to precess. We present polarimetric radio observations of the pulsar PSR J1906+0746 that demonstrate the validity of the geometrical model of pulsar polarization. We reconstruct the (sky-projected) polarization emission map over the pulsar’s magnetic pole and predict the disappearance of the detectable emission by 2028. Two tests of GR are performed using this system, including the spin precession for strongly self-gravitating bodies. We constrain the relativistic treatment of the pulsar polarization model and measure the pulsar beaming fraction, with implications for the population of neutron stars and the expected rate of neutron star mergers

BlackHoleCam -- Testing general relativity with pulsars orbiting Sagittarius A*

BlackHoleCam is a project funded by a European Research Council Synergy Grant to build a complete astrophysical description of nearby supermassive black holes by using a combination of radio imaging, pulsar observations, stellar astrometry and general relativistic magneto-hydrodynamic models. BlackHoleCam scientists are active partners of the Event Horizon Telescope Consortium. In this talk I will discuss the use of pulsars orbiting Sagittarius A* for tests of General Relativity, the current difficulties in detecting such sources, recent results from the Galactic Centre magnetar PSR J1745-2900 and how BlackHoleCam aims to search for undiscovered pulsars in the Galactic Centre.Comment: 4 pages, 3 figures, Proceedings of The Fifteenth Marcel Grossmann Meeting on General Relativity, University of Rome La Sapienza, Italy, 1 - 7 July 201

A Gaussian-processes approach to fitting for time-variable spherical solar wind in pulsar timing data

Propagation effects are one of the main sources of noise in high-precision pulsar timing. For pulsars below an ecliptic latitude of 5°, the ionized plasma in the solar wind can introduce dispersive delays of order 100 µs around solar conjunction at an observing frequency of 300 MHz. A common approach to mitigate this assumes a spherical solar wind with a time-constant amplitude. However, this has been shown to be insufficient to describe the solar wind. We present a linear, Gaussian-process piecewise Bayesian approach to fit a spherical solar wind of time-variable amplitude, which has been implemented in the pulsar software RUN_ENTERPRISE. Through simulations, we find that the current EPTA+InPTA data combination is not sensitive to such variations; however, solar wind variations will become important in the near future with the addition of new InPTA data and data collected with the low-frequency LOFAR telescope. We also compare our results for different high-precision timing data sets (EPTA+InPTA, PPTA, and LOFAR) of 3 ms pulsars (J0030+0451, J1022+1001, J2145−0450), and find that the solar-wind amplitudes are generally consistent for any individual pulsar, but they can vary from pulsar to pulsar. Finally, we compare our results with those of an independent method on the same LOFAR data of the three millisecond pulsars. We find that differences between the results of the two methods can be mainly attributed to the modelling of dispersion variations in the interstellar medium, rather than the solar wind modelling

Compensatory T Cell Responses in IRG-Deficient Mice Prevent Sustained Chlamydia trachomatis Infections

The obligate intracellular pathogen Chlamydia trachomatis is the most common cause of bacterial sexually transmitted diseases in the United States. In women C. trachomatis can establish persistent genital infections that lead to pelvic inflammatory disease and sterility. In contrast to natural infections in humans, experimentally induced infections with C. trachomatis in mice are rapidly cleared. The cytokine interferon-γ (IFNγ) plays a critical role in the clearance of C. trachomatis infections in mice. Because IFNγ induces an antimicrobial defense system in mice but not in humans that is composed of a large family of Immunity Related GTPases (IRGs), we questioned whether mice deficient in IRG immunity would develop persistent infections with C. trachomatis as observed in human patients. We found that IRG-deficient Irgm1/m3(-/-) mice transiently develop high bacterial burden post intrauterine infection, but subsequently clear the infection more efficiently than wildtype mice. We show that the delayed but highly effective clearance of intrauterine C. trachomatis infections in Irgm1/m3(-/-) mice is dependent on an exacerbated CD4+ T cell response. These findings indicate that the absence of the predominant murine innate effector mechanism restricting C. trachomatis growth inside epithelial cells results in a compensatory adaptive immune response, which is at least in part driven by CD4+ T cells and prevents the establishment of a persistent infection in mice

Erratum: 'A precise mass measurement of the intermediate-mass binary pulsar PSR J1802-2124' (2010, ApJ, 711, 764)

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