A5101509725- Pulsars and Gravitational Waves Research
- Geophysics and Gravity Measurements
- Radio Astronomy Observations and Technology
- Advanced Frequency and Time Standards
- GNSS positioning and interference
- Gamma-ray bursts and supernovae
- Cosmology and Gravitation Theories
- Superconducting Materials and Applications
- Astrophysics and Cosmic Phenomena
- Geophysics and Sensor Technology
- Solar and Space Plasma Dynamics
- Stellar, planetary, and galactic studies
- Inertial Sensor and Navigation
- Target Tracking and Data Fusion in Sensor Networks
- Energy Efficient Wireless Sensor Networks
- Particle accelerators and beam dynamics
- Dark Matter and Cosmic Phenomena
- Particle Detector Development and Performance
- Astrophysics and Star Formation Studies
- Black Holes and Theoretical Physics
- Astronomical Observations and Instrumentation
- Astrophysical Phenomena and Observations
- Ionosphere and magnetosphere dynamics
- Indoor and Outdoor Localization Technologies
- Seismic Waves and Analysis
Southwest University
2011-2024
Wenzhou University
2012
University of Chinese Academy of Sciences
2007
National Astronomical Observatories
2007
Chinese Academy of Sciences
2007
Australia Telescope National Facility
2007
Commonwealth Scientific and Industrial Research Organisation
2007
The International Pulsar Timing Array project combines observations of pulsars from both northern and southern hemisphere observatories with the main aim detecting ultra-low frequency (∼ 10−9–10−8 Hz) gravitational waves. Here we introduce project, review methods used to search for waves emitted coalescing supermassive binary black-hole systems in centres merging galaxies discuss status project.
A "pulsar timing array" (PTA), in which observations of a large sample pulsars spread across the celestial sphere are combined, allows investigation "global" phenomena such as background gravitational waves or instabilities atomic timescales that produce correlated residuals array. The Parkes Pulsar Timing Array (PPTA) is an implementation PTA concept based on with 64-m radio telescope. 20 millisecond being observed at three radio-frequency bands, 50cm (~700 MHz), 20cm (~1400 MHz) and 10cm...
The highly stable spin of neutron stars can be exploited for a variety (astro)physical investigations. In particular, arrays pulsars with rotational periods the order milliseconds used to detect correlated signals such as those caused by gravitational waves. Three ‘pulsar timing arrays’ (PTAs) have been set up around world over past decades and collectively form ‘International’ PTA (IPTA). this paper, we describe first joint analysis data from three regional PTAs, i.e. IPTA set. We available...
We present timing models for 20 millisecond pulsars in the Parkes Pulsar Timing Array. The precision of parameter measurements these has been improved over earlier results by using longer data sets and modelling non-stationary noise. describe a new noise procedure demonstrate its effectiveness simulated data. Our methodology includes addition annual dispersion measure (DM) variations to some pulsars. first significant parallax PSRs J1024−0719, J1045−4509, J1600−3053, J1603−7202, J1730−2304,...
Quantum fluctuations of the gravitational field in early Universe, amplified by inflation, produce a primordial gravitational-wave background across broad frequency band. We derive constraints on spectrum this radiation, and hence theories combining experiments that cover 29 orders magnitude frequency. These include Planck observations cosmic microwave temperature polarization power spectra lensing, together with baryon acoustic oscillations big bang nucleosynthesis measurements, as well new...
Abstract Discovery of pulsars is one the main goals for large radio telescopes. The Five-hundred-meter Aperture Spherical Telescope (FAST), that incorporates an L-band 19-beam receiver with a system temperature about 20 K, most sensitive telescope utilized discovering pulsars. We designed snapshot observation mode FAST key science project, Galactic Plane Pulsar Snapshot (GPPS) survey, in which every four nearby pointings can observe cover sky patch 0.1575 square degrees through...
Using observations of pulsars from the Parkes Pulsar Timing Array (PPTA) project we develop first pulsar-based timescale that has a precision comparable to uncertainties in international atomic timescales.Our ensemble provides an Ensemble Scale (EPS) analogous free Échelle Atomique Libre (EAL).The EPS can be used detect fluctuations timescales and therefore lead new realisation Terrestrial Time, TT(PPTA11).We successfully follow features known affect frequency International Atomic Timescale...
The analysis of high-precision timing observations an array ∼20 millisecond pulsars (a so-called 'timing array') may ultimately result in the detection a stochastic gravitational-wave background. feasibility such and required duration this type experiment are determined by achievable rms residuals stability involved. We present results first long-term, campaign on large sample used projects. show that most our do not contain significant low-frequency noise could limit use these for...
Pulsar timing array experiments search for phenomena that produce angular correlations in the arrival times of signals from millisecond pulsars. The primary goal is to detect an isotropic and stochastic gravitational wave background. We use simulated data show this can be affected by presence other spatially correlated noise, such as errors reference time standard, planetary ephemeris, solar wind instrumentation issues. All these effects induce significant false detections waves. test...
We analyse the stochastic properties of 49 pulsars that comprise first International Pulsar Timing Array (IPTA) data release. use Bayesian methodology, performing model selection to determine optimal description signals present in each pulsar. In addition spin-noise and dispersion-measure (DM) variations, these models can include timing noise unique a single observing system, or frequency band. show improved radio-frequency coverage presence overlapping from different systems IPTA set...
It is widely accepted that dark matter contributes about a quarter of the critical mass-energy density in our Universe. The nature currently unknown, with mass possible constituents spanning nearly one hundred orders magnitude. ultralight scalar field matter, consisting extremely light bosons m∼10−22 eV and often called “fuzzy” provides intriguing solutions to some challenges at sub-Galactic scales for standard cold model. As shown by Khmelnitsky Rubakov, such Galaxy would produce an...
Extreme scattering events (ESEs) in the interstellar medium (ISM) were first observed regular flux measurements of compact extragalactic sources. They are characterized by a variation over period weeks, suggesting passage "diverging plasma lens" across line sight. Modeling refraction such lens indicates that structure size must be order AU and electron density 10s cm^{-3}. Similar structures have been pulsar intensity scintillation group delay. Here we report observations two ESEs showing...
Measurement of the pulsar timing residuals provides a direct way to detect relic gravitational waves at frequency $f\sim 1/{\rm yr}$. In this paper, we investigate constraints on inflationary parameters, tensor-to-scalar ratio $r$ and tensor spectral index $n_t$, by current future Pulsar Timing Arrays (PTAs). We find that Five-hundred-meter Aperture Spherical radio Telescope (FAST) in China planned Square Kilometer Array (SKA) projects have fairly strong abilities test phantom-like models....
Abstract We have carried out the Galactic Plane Pulsar Snapshot (GPPS) survey by using Five-hundred-meter Aperture Spherical radio Telescope (FAST), most sensitive systematic pulsar in plane. In addition to more than 500 pulsars already discovered through normal periodical search, we report here discovery of 76 new transient sources with sporadic strong pulses, detected newly developed module for a single-pulse search. Their small DM values suggest that they all are rotating transients...
We present an analysis of the variations seen in dispersion measures (DMs) 20 millisecond pulsars observed as part Parkes Pulsar Timing Array project. carry out a statistically rigorous structure function for each pulsar and show that most are consistent with those expected interstellar medium characterised by Kolmogorov turbulence spectrum. The functions PSRs J1045-4509 J1909-3744 provide first clear evidence large inner scale, possibly due to ion-neutral damping. also effect solar wind on...
Variations in the solar wind density introduce variable delays into pulsar timing observations. Current analysis programs only implement simple models of wind, which not limit accuracy, but can also affect measurements rotational, astrometric, and orbital parameters. We describe a new model electron content uses observations from Wilcox Solar Observatory magnetic field. have implemented this TEMPO2 package. show that is more accurate than previous these corrections are necessary for...
Abstract The first direct detection of gravitational waves may be made through observations pulsars. principal aim pulsar timing-array projects being carried out worldwide is to detect ultra-low frequency ( f ∼ 10 −9 –10 −8 Hz). Such are expected caused by coalescing supermassive binary black holes in the cores merged galaxies. It also possible that a detectable signal could have been produced inflationary era or cosmic strings. In this paper, we review current status Parkes Pulsar Timing...
The magnetic field of the solar wind near Sun is very difficult to measure directly. Measurements Faraday rotation linearly polarized radio sources occulted by provide a unique opportunity estimate this field, and technique has been widely used in past. However path integral product electron density projection on path. can be measured several methods, but it quite variable. Here we show that possible integrated simultaneously at 6-10 $R_\odot$ using millisecond pulsars as source. By...
By regularly monitoring the most stable millisecond pulsars over many years, pulsar timing arrays (PTAs) are positioned to detect and study correlations in behaviour of those pulsars. Gravitational waves (GWs) from supermassive black hole binaries (SMBHBs) an exciting potentially detectable source such correlations. We describe a straightforward technique by which PTA can be ‘phased-up’ form time series two polarization modes GWs coming particular direction sky. Our requires no assumptions...
ABSTRACT Timing observations are crucial for determining the basic parameters of newly discovered pulsars. Using Five-hundred-meter Aperture Spherical radio Telescope (FAST) with L-band 19-beam receiver covering frequency range 1.0–1.5 GHz, FAST Galactic Plane Pulsar Snapshot (GPPS) Survey has more than 600 faint pulsars flux densities only a few or tens μJy at 1.25 GHz. To obtain accurate position, spin and dispersion measure pulsar, to calculate derived such as characteristic age surface...
ABSTRACT Double neutron star (DNS) systems offer excellent opportunities to test gravity theories. We report the timing results of PSR J1901+0658, first pulsar discovered in FAST Galactic Plane Pulsar Snapshot (GPPS) Survey. Based on observations by over 5 yr, we obtain phase-coherent solution and derive precise measurements its position, spin parameters, orbital dispersion measure. It has a period 75.7 ms, derivative 2.169(6) × 10−19 s s−1, characteristic age 5.5 Gyr. This is an orbit with...
Abstract The Five-hundred-meter Aperture Spherical radio Telescope (FAST) is the most sensitive telescope at L -band (1.0–1.5 GHz) and has been used to carry out FAST Galactic Plane Pulsar Snapshot (GPPS) survey in last 5 yr. Up now, covered one-fourth of planned areas within ±10 ∘ from plane visible by FAST, discovered 751 pulsars. After first publication discovery 201 pulsars one rotating transient (RRAT) 2021 76 RRATs 2023, here we report 473 new GPPS survey, including 137 millisecond 30...
Pulsar timing has enabled some of the strongest tests fundamental physics. Central to technique is assumption that detected radio pulses can be used accurately measure rotation pulsar. Here we report on a broad-band variation in pulse profile millisecond pulsar J1643-1224. A new component emission suddenly appears profile, decays over 4 months, and results permanently modified shape. Profile variations such as these may origin noise observed other pulsars. The sensitivity pulsar-timing...