John Sarkissian
A5058763141- Pulsars and Gravitational Waves Research
- Geophysics and Gravity Measurements
- Radio Astronomy Observations and Technology
- Gamma-ray bursts and supernovae
- Astrophysical Phenomena and Observations
- Advanced Frequency and Time Standards
- Astrophysics and Cosmic Phenomena
- Stellar, planetary, and galactic studies
- Superconducting Materials and Applications
- GNSS positioning and interference
- Geophysics and Sensor Technology
- High-pressure geophysics and materials
- Astro and Planetary Science
- Cosmology and Gravitation Theories
- Classical Antiquity Studies
- Astronomical Observations and Instrumentation
- Planetary Science and Exploration
- Classical Philosophy and Thought
- Solar and Space Plasma Dynamics
- Organic Chemistry Synthesis Methods
- Particle Accelerators and Free-Electron Lasers
- Space exploration and regulation
- Space Science and Extraterrestrial Life
- Cold Atom Physics and Bose-Einstein Condensates
- Superconducting and THz Device Technology
Australia Telescope National Facility
2012-2024
Astronomy and Space
2012-2024
Commonwealth Scientific and Industrial Research Organisation
2014-2024
L. A. Orbeli Institute of Physiology NAS RA
2023-2024
Armenian State Pedagogical University after Khachatur Abovian
2023
Astronomy Australia
2021
Vitenparken
2020
Max Planck Institute for Radio Astronomy
2015
Max Planck Society
2015
SKA Observatory
2005-2007
The double pulsar system PSR J0737-3039A/B is unique in that both neutron stars are detectable as radio pulsars. They also known to have much higher mean orbital velocities and accelerations than those of other binary therefore a good candidate for testing Einstein's theory general relativity alternative theories gravity the strong-field regime. We report on precision timing observations taken over 2.5 years since its discovery present four independent tests relativity. These use...
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...
We searched for an isotropic stochastic gravitational wave background in the second data release of International Pulsar Timing Array, a global collaboration synthesizing decadal-length pulsar-timing campaigns North America, Europe, and Australia. In our reference search power law strain spectrum form $h_c = A(f/1\,\mathrm{yr}^{-1})^{\alpha}$, we found strong evidence spectrally-similar low-frequency process amplitude $A 3.8^{+6.3}_{-2.5}\times10^{-15}$ spectral index $\alpha -0.5 \pm 0.5$,...
Continued observations of the Double Pulsar, PSR J0737-3039A/B, consisting two radio pulsars (A and B) that orbit each other with a period 2.45hr in mildly eccentric (e=0.088) binary system, have led to large improvements measurement relativistic effects this system. With 16-yr data span, results enable precision tests theories gravity for strongly self-gravitating bodies also reveal new been expected but are now observed first time. These include light propagation strong gravitational...
Abstract We present the third data release from Parkes Pulsar Timing Array (PPTA) project. The contains observations of 32 pulsars obtained using 64-m ‘Murriyang’ radio telescope. span is up to 18 yr with a typical cadence 3 weeks. This formed by combining an updated version our second $\sim$ more recent primarily ultra-wide-bandwidth receiver system that operates between 704 and 4032 MHz. provide calibrated pulse profiles, flux density dynamic spectra, times arrival, initial pulsar timing...
Using a statistically rigorous analysis method, we place limits on the existence of an isotropic stochastic gravitational wave background using pulsar timing observations. We consider backgrounds whose characteristic strain spectra may be described as power-law dependence with frequency. Such include astrophysical produced by coalescing supermassive black-hole binary systems and cosmological due to relic waves cosmic strings. best available data, obtain upper limit energy density per unit...
Signals from radio pulsars show a wavelength-dependent delay due to dispersion in the interstellar plasma. At typical observing wavelength, this can vary by tens of microseconds on five-year time scales, far excess signals interest pulsar timing arrays, such as that induced gravitational-wave background. Measurement these variations is not only crucial for detection signals, but also provides an unparallelled measurement turbulent plasma at au scales. In paper we demonstrate without...
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...
Timing observations from the Parkes 64-m radio telescope for 165 pulsars between 1990 and 2011 have been searched period glitches. A total of 107 glitches were identified in 36 pulsars, where 61 previously reported 46 are new discoveries. Glitch parameters measured by fitting timing residual data. Observed relative glitch sizes \Delta\nu_g/\nu range 10^-10 10^-5, \nu = 1/P is pulse frequency. We confirm that distribution bimodal with peaks at approximately 10^-9 10^-6. Glitches mostly...
Abstract We describe 14 yr of public data from the Parkes Pulsar Timing Array (PPTA), an ongoing project that is producing precise measurements pulse times arrival 26 millisecond pulsars using 64-m radio telescope with a cadence approximately 3 weeks in three observing bands. A comprehensive description pulsar systems employed at since 2004 provided, including calibration methodology and analysis stability system components. attempt to provide full accounting reduction raw measured Stokes...
We present high signal-to-noise ratio, multifrequency polarization pulse profiles for 24 millisecond pulsars that are being observed as part of the Parkes Pulsar Timing Array project. The in three bands, centred close to 730, 1400 and 3100 MHz, using a dual-band 10 cm/50 cm receiver central beam 20-cm multibeam receiver. Observations spanning approximately six years have been carefully calibrated summed produce S/N profiles. This allows us study individual profile components particular how...
This paper is the second in a series where we report results of long-term timing millisecond pulsars (MSPs) 47 Tucanae with Parkes 64-m radio telescope. We obtain improved parameters that provide additional information for studies cluster dynamics: a) pulsar proper motions yield an estimate motion as whole ($\mu_{\alpha}\, = \, 5.00\, \pm 0.14\, \rm mas yr^{-1}$, $\mu_{\delta}\, -2.84\, 0.12\, yr^{-1}$) and relative to each other. b) measure spin-period derivatives caused by change...
High-sensitivity radio-frequency observations of millisecond pulsars usually show stochastic, broadband, pulse-shape variations intrinsic to the pulsar emission process. These induce jitter noise in timing observations; understanding properties this is particular importance for effort detect gravitational waves with arrays. We assess short-term profile and stability 22 that are part Parkes Pulsar Timing Array sample by examining intra-observation arrival time variability single-pulse...
We present the sensitivity of Parkes Pulsar Timing Array to gravitational waves emitted by individual super-massive black-hole binary systems in early phases coalescing at cores merged galaxies. Our analysis includes a detailed study effects fitting pulsar timing model non-white residuals. is sensitive nanoHertz frequencies and hence complementary LIGO LISA. place sky-averaged constraint on merger rate nearby ($z < 0.6$) binaries coalescence with chirp mass $10^{10}\,\rmn{M}_\odot$ less than...
In a search with the Parkes radio telescope of 56 unidentified Fermi-LAT gamma-ray sources, we have detected 11 millisecond pulsars (MSPs), 10 them discoveries, which five were reported in Kerr et al. (2012). We did not detect pulsations from another six now known these sources. describe completed survey, included multiple observations many targets done to minimize impact interstellar scintillation, acceleration effects binary systems, and eclipses. consider that 23 39 remaining sources may...
'Perytons' are millisecond-duration transients of terrestrial origin, whose frequency-swept emission mimics the dispersion an astrophysical pulse that has propagated through tenuous cold plasma. In fact, their similarity to FRB 010724 had previously cast a shadow over interpretation 'fast radio bursts' (FRBs), which otherwise appear be extragalactic origin. Until now, physical origin dispersion-mimicking perytons remained mystery. We have identified strong out-of-band at 2.3–2.5 GHz...
New radio (MeerKAT and Parkes) X-ray (XMM-Newton, Swift, Chandra, NuSTAR) observations of PSR J1622-4950 indicate that the magnetar, in a quiescent state since at least early 2015, reactivated between 2017 March 19 April 5. The flux density, while variable, is approximately 100x larger than during its dormant state. one month after reactivation was 800x quiescence, has been decaying exponentially on 111+/-19 day timescale. This high-flux state, together with radio-derived rotational...
For the past couple of decades, Parkes radio telescope has been regularly observing millisecond pulsars in 47 Tucanae (47 Tuc). This long-term timing program was designed to address a wide range scientific issues related these and globular cluster where they are located. In this paper, first series, we one objectives: characterization four previously known binary for which no precise orbital parameters were known, namely Tuc P, V, W X (pulsars R Y discussed elsewhere). We determined unknown...
We describe an ultra-wide-bandwidth, low-frequency receiver ("UWL") recently installed on the Parkes radio telescope. The system provides continuous frequency coverage from 704 to 4032 MHz. For much of band (~60%) temperature is approximately 22K and remains in a linear regime even presence strong mobile phone transmissions. discuss scientific technical aspects new including its astronomical objectives, as well feed, receiver, digitiser signal-processor design. pipeline routines that form...
Abstract Radio emission from magnetars provides a unique probe of the relativistic, magnetized plasma within near-field environment these ultra-magnetic neutron stars. The transmitted waves can undergo birefringent and dispersive propagation effects that result in frequency-dependent conversions linear to circularly polarized radiation vice versa, thus necessitating classification when relating measured polarization intrinsic properties star fast radio burst sites. We report detection such...
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...