RFI mitigation at Nanc¸ay Observatory: Impulsive Signal Processing

Radio astronomy has protected frequency bands for free observations. However, it is often necessary to observe outside of those sanctuaries. For example, it is the case for HI radio-sources with high red-shifts that are observed into radarallocated frequency bands. A radar pulse blanker based on statistical analysis has been implemented in a FPGA. Several tricks has made the implementation possible at a low hardware cost. Pulsar is another kind of impulsive signal which needs specific processing. In the proposed approach, the cyclostationarity is used to discriminate between radio-frequency interference (RFI) pulses and pulsar pulses

The INPOP10a planetary ephemeris and its applications in fundamental physics

International audienceCompared to the previous INPOP versions, the INPOP10a planetary and lunar ephemeris has several improvements. For the planets of our solar system, no big change was brought in the dynamics but improvements were implemented in the fitting process, the data sets used in the fit and in the selection of fitted parameters. We report here the main characteristics of the planetary part of INPOP10a like the fit of the product of the Solar mass with the gravitational constant (GM$_{\odot}$) instead of the astronomical unit. Determinations of PPN parameters as well as adjustments of the Sun J2 and of asteroid masses are also presented. New advances of nodes and perihelia of planets were also estimated and are given here. As for INPOP08, INPOP10a provides to the user, positions and velocities of the planets, the moon, the rotation angles of the Earth and the Moon as well as TT-TDB chebychev polynomials at http://www.imcce.fr/inpo

Pulsar observing at the Nançay Radio Telescope : surveys, studies of relativistic binary systems and detection of the gravitational wave background

Un pulsar est une étoile à neutrons en rotation rapide et dotée d'un fort champ magnétique qui peut se manifester en émettant sur tout le spectre électromagnétique. Dans cette thèse, je m’intéresse au rayonnement radio produit par l’étoile. Je commence ainsi par décrire l'instrumentation de dédispersion cohérente à base de GPUs installée au Radiotélescope de Nançay avec deux autres modes d'observation que j'ai développés : un mode pour la recherche de nouveaux pulsar et un mode spectromètre. Une autre partie de ce travail détaille le retraitement en cours du sondage Foster fait à la fin des années 90 à Nançay ainsi que de nouvelles observations ciblées, sur des candidats HESS notamment. Je présente ensuite les résultats obtenus sur les pulsars relativistes J0737-3039A et J1906+0746 avec respectivement des tests de la Relativité Générale et la mesure de la précession géodétique. Des données de polarimétrie ont ainsi permis de déterminer la géométrie du système de PSR J1906+0746. Enfin, je termine par l'analyse des temps d'arrivées de 20 pulsars millisecondes observés à Nançay dans le cadre de l'EPTA, une collaboration européenne pour un réseau de chronométrage pulsar avec pour objectif la détection d'un fond d'ondes gravitationnelles, possible d'ici 5 à 10 ans.A pulsar is a highly magnetized and fast-spinning neutron star which can be seen in radio waves. ln this thesis, l first describe the new GPU-based coherent dedispersion backend installed at the Nançay Radio Telescope with two others observing modes l have developped : a filterbank for(pulsar surveysjand a high resolution spectrometer. The second part deals with the ongoing reprocessing of the Foster survey done at Nançay in the late 90s and with new targeted pointings on HESS sources. l then present the results l got on the relativistic binaries J0737-3039A et J1906+0746, with new tests of General Relativity and the measurement of geodetic precession respectively. Polarimetric data has allowed to deduce the geometry of the PSR J1906+0746 system. ln the framework of the EPTA (European Pulsar Timing Array), l finish with the analysis of the times of arrivaIs from 20 millisecond pulsars, which aims to make a detection of the Gravitational Wave Background, which could succeed in the next 5 to 10 years

Search for and study of pulsars with the Nançay Radio Telescope

International audienceSince 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

An improved test of the strong equivalence principle with the pulsar in a triple star system

Accepted in A&AInternational audienceContext. The gravitational strong equivalence principle (SEP) is a cornerstone of the general theory of relativity (GR). Hence, testing the validity of SEP is of great importance when confronting GR, or its alternatives, with experimental data. Pulsars that are orbited by white dwarf companions provide an excellent laboratory, where the extreme difference in binding energy between neutron stars and white dwarfs allows for precision tests of the SEP via the technique of radio pulsar timing.Aims: To date, the best limit on the validity of SEP under strong-field conditions was obtained with a unique pulsar in a triple stellar system, PSR J0337+1715. We report here on an improvement of this test using an independent data set acquired over a period of 6 years with the Nançay radio telescope. The improvements arise from a uniformly sampled data set, a theoretical analysis, and a treatment that fixes some short-comings in the previously published results, leading to better precision and reliability of the test.Methods: In contrast to the previously published test, we use a different long-term timing data set, developed a new timing model and an independent numerical integration of the motion of the system, and determined the masses and orbital parameters with a different methodology that treats the parameter Δ, describing a possible strong-field SEP violation, identically to all other parameters.Results: We obtain a violation parameter Δ = ( + 0.5 ± 1.8) × 10-6 at 95% confidence level, which is compatible with and improves upon the previous study by 30%. This result is statistics-limited and avoids limitation by systematics as previously encountered. We find evidence for red noise in the pulsar spin frequency, which is responsible for up to 10% of the reported uncertainty. We use the improved limit on SEP violation to place constraints on a class of well-studied scalar-tensor theories, in particular we find ωBD > 140 000 for the Brans-Dicke parameter. The conservative limits presented here fully take into account current uncertainties in the equation for state of neutron-star matter

A Massive-born Neutron Star with a Massive White Dwarf Companion

International audienceWe report on the results of a 4-year timing campaign of PSR J2222−0137, a 2.44-day binary pulsar with a massive white dwarf (WD) companion, with the Nançay, Effelsberg and Lovell radio telescopes. Using the Shapiro delay for this system, we find a pulsar mass m p = 1.76 ± 0.06 M and a WD mass m c = 1.293 ± 0.025 M. We also measure the rate of advance of periastron for this system, which is marginally consistent with the GR prediction for these masses. The short lifetime of the massive WD progenitor star led to a rapid X-ray binary phase with little (< 10 −2 M) mass accretion onto the neutron star (NS); hence, the current pulsar mass is, within uncertainties, its birth mass, which is the largest measured to date. We discuss the discrepancy with previous mass measurements for this system; we conclude that the measurements presented here are likely to be more accurate. Finally, we highlight the usefulness of this system for testing alternative theories of gravity by tightly constraining the presence of dipolar radiation. This is of particular importance for certain aspects of strong-field gravity, like spontaneous scalarization, since the mass of PSR J2222−0137 puts that system into a poorly tested parameter range

Replacing <i>TrkA</i> with <i>TrkAC</i> is compatible with grossly normal survival of sensory neurons in <i>TrkAC-KI</i> mice.

<p>(A,B) An <i>in situ</i> probe recognizing endogenous <i>TrkA</i>, but not chimeric <i>TrkAC</i> is labeling the majority of wild type E15.5 DRG neurons, while mutant DRGs lack any staining. (C,D) An <i>in situ</i> probe specific to both <i>TrkC</i> and chimeric <i>TrkAC</i> is labeling few TrkC-positive neurons in wild type embryos and the majority of neurons in the E15.5 mutant DRGs. (E,F) Immunostaining with a TrkA antibody recognizing both TrkA and TrkAC (red) and a TrkC-specific antibody (green) showing normal pattern of TrkC expression and comparable TrkA antibody immunoreactivity in E15.5 mutant DRG. (G,H) There is normal TrkA antibody immunoreactivity in DRGs from P0 <i>TrkAC-KI</i> mutant mice. (I) Total number of lumbar (L3–4) and thoracic (T11–12) DRG neurons is reduced by 16% and 18% respectively in <i>TrkAC-KI</i> mice. Data represent mean ± s.e.m. Lumbar counts: 9 mutant and 8 wild type DRGs from 4 animals for each genotype, p = 0.041; thoracic counts: 8 mutant and 6 wild type DRGs from 3 and 2 animals respectively, p = 0.0019. * p<0.05, ** p<0.01. Scale bar is 50 µm.</p

Peripheral, but not central innervation is drastically reduced in TrkAC-KI mice.

<p>(A–D) Peptidergic (CGRP-positive) and total (PGP9.5-positive) fiber innervation is decreased in thick glabrous skin of adult <i>TrkAC-KI</i> hindlimbs. (E) Free nerve endings (FNE) counts in thick glabrous skin. Shown are means ± s.e.m. from 8–10 sections from two animals per genotype (* p>0.05, ** p<0.01). (F–I) Peptidergic (CGRP-positive) and total (PGP9.5-positive) fiber innervation is decreased in thin glabrous skin of adult <i>TrkAC-KI</i> hindlimbs. (J) Free nerve ending (FNE) counts in thin glabrous skin. Shown are means ± s.e.m. from 8–10 sections from two animals per genotype (* p>0.05, ** p<0.01). (K,L) Central projections are normal in <i>TrkAC-KI</i> mice. Peptidergic (CGRP-positive, green) and nonpeptidergic(IB4-positive, red) fibers normally innervate adult spinal cord in <i>TrkAC-KI</i> mice. Scale bar is 50 µm.</p

Abnormal mechanical and chemical pain response in <i>TrkAC-KI</i> mice.

<p>(A) Latency to mechanical stimulation using Von Frey apparatus was significantly lower in control mice one day after CFA injection, while <i>TrkAC-KI</i> mice did not show this response. Of note, the baseline latency to mechanical stimulation was lower in mutant mice (n = 9 for wild type and 13 for <i>TrkAC-KI</i>). (B) Lack of mechanical hypersensitivity after inflammation was also evident from a Dynamic Weight Bearing test. For <i>TrkAC-KI</i> mice, the weight distribution between inflamed and non-inflamed hindpaws was equal one day after CFA injection, while control mice favored the non-injected paw (n = 10 for wild type and 9 for <i>TrkAC-KI</i>). (C) Both <i>TrkAC-KI</i> and control mice developed thermal hyperalgesia one day after CFA injection (n = 8 for wild type and 6 for <i>TrkAC-KI</i>). The CFA effect (difference in latency between Day0 and day CFA+1) was significantly different between <i>TrkAC-KI</i> and wild type mice for Von Frey and DWB tests (A and B), but not for Hargreaves test (C). (D) <i>TrkAC-KI</i> mice exhibited severe deficit in pain from chemical injury when tested for nociceptive response after intraplantar injection of 10 µl of 2% formalin. Comparing to wild type littermates, <i>TrkAC-KI</i> mice had drastically reduced time of hindpaw shaking and biting during the first (0–10 min) and second (15–60 min) pain phases (n = 7 for each genotype). Data represent mean ± s.e.m * p<0.05, ** p<0.01.</p