Tomonosuke Kikunaga
A5033648308- Pulsars and Gravitational Waves Research
- Radio Astronomy Observations and Technology
- GNSS positioning and interference
- Geophysics and Gravity Measurements
- Advanced Frequency and Time Standards
- Gamma-ray bursts and supernovae
- Cosmology and Gravitation Theories
- Seismic Imaging and Inversion Techniques
- Seismic Waves and Analysis
- Astrophysics and Cosmic Phenomena
- Image and Signal Denoising Methods
- Statistical and numerical algorithms
- Astrophysical Phenomena and Observations
- Superconducting and THz Device Technology
Kumamoto University
2021-2024
Australia Telescope National Facility
2023-2024
Commonwealth Scientific and Industrial Research Organisation
2023-2024
We present the results of search for an isotropic stochastic gravitational wave background (GWB) at nanohertz frequencies using second data release European Pulsar Timing Array (EPTA) 25 millisecond pulsars and a combination with first Indian (InPTA). analysed (i) full 24.7-year EPTA set, (ii) its 10.3-year subset based on modern observing systems, (iii) set InPTA ten commonly timed pulsars, (iv) data. These combinations allowed us to probe contributions instrumental noise interstellar...
The European Pulsar Timing Array (EPTA) and Indian (InPTA) collaborations have measured a low-frequency common signal in the combination of their second first data releases, respectively, with correlation properties gravitational wave background (GWB). Such may its origin number physical processes including cosmic population inspiralling supermassive black hole binaries (SMBHBs); inflation, phase transitions, strings, tensor mode generation by non-linear evolution scalar perturbations early...
The European Pulsar Timing Array (EPTA) and Indian (InPTA) collaborations have measured a low-frequency common signal in the combination of their second first data releases respectively, with correlation properties gravitational wave background (GWB). Such may its origin number physical processes including cosmic population inspiralling supermassive black hole binaries (SMBHBs); inflation, phase transitions, strings tensor mode generation by non-linear evolution scalar perturbations early...
Aims. The nanohertz gravitational wave background (GWB) is expected to be an aggregate signal of ensemble waves emitted predominantly by a large population coalescing supermassive black hole binaries in the centres merging galaxies. Pulsar timing arrays (PTAs), which are ensembles extremely stable pulsars at approximately kiloparsec distances precisely monitored for decades, most precise experiments capable detecting this background. However, subtle imprints that GWB induces on pulsar data...
We present the results of a search for continuous gravitational wave signals (CGWs) in second data release (DR2) European Pulsar Timing Array (EPTA) Collaboration. The most significant candidate event from this has frequency 4–5 nHz. Such signal could be generated by supermassive black hole binary (SMBHB) local Universe. follow-up analysis using both Bayesian and frequentist methods. gives Bayes factor 4 favour presence CGW over common uncorrelated noise process. In contrast, estimates...
We present the pulse arrival times and high-precision dispersion measure estimates for 14 millisecond pulsars observed simultaneously in 300-500 MHz 1260-1460 frequency bands using upgraded Giant Metrewave Radio Telescope (uGMRT). The data spans over a baseline of 3.5 years (2018-2021), is first official release made available by Indian Pulsar Timing Array collaboration. This presents unique opportunity investigating interstellar medium effects at low radio frequencies their impact on timing...
We present the results of search for an isotropic stochastic gravitational wave background (GWB) at nanohertz frequencies using second data release European Pulsar Timing Array (EPTA) 25 millisecond pulsars and a combination with first Indian (InPTA). analysed (i) full 24.7-year EPTA set, (ii) its 10.3-year subset based on modern observing systems, (iii) set InPTA ten commonly timed pulsars, (iv) data. These combinations allowed us to probe contributions instrumental noise interstellar...
We present the results of a search for continuous gravitational wave signals (CGWs) in second data release (DR2) European Pulsar Timing Array (EPTA) collaboration. The most significant candidate event from this has frequency 4-5 nHz. Such signal could be generated by supermassive black hole binary (SMBHB) local Universe. follow-up analysis using both Bayesian and frequentist methods. gives Bayes factor 4 favor presence CGW over common uncorrelated noise process, while estimates p-value to...
PSR J1713+0747 is one of the most precisely timed pulsars in international pulsar timing array experiment. This showed an abrupt profile shape change between April 16, 2021 (MJD 59320) and 17, 59321). In this paper, we report results from multi-frequency observations carried out with upgraded Giant Metrewave Radio Telescope (uGMRT) before after event. We demonstrate seen Band 5 (1260 MHz - 1460 MHz) 3 (300 500 MHz). The analysis shows a disturbance accompanying followed by recovery timescale...
High-precision measurements of the pulsar dispersion measure (DM) are possible using telescopes with low-frequency wideband receivers. We present an initial study application timing technique, which can simultaneously times arrival (ToAs) and DMs, for a set five pulsars observed upgraded Giant Metrewave Radio Telescope (uGMRT) as part Indian Pulsar Timing Array (InPTA) campaign. have used observations 300-500 MHz band uGMRT this purpose. obtain high precision in DM precisions order...
The nanohertz gravitational wave background (GWB) is expected to be an aggregate signal of ensemble waves emitted predominantly by a large population coalescing supermassive black hole binaries in the centres merging galaxies. Pulsar timing arrays, ensembles extremely stable pulsars, are most precise experiments capable detecting this background. However, subtle imprints that GWB induces on pulsar data obscured many sources noise. These must carefully characterized increase sensitivity GWB....
The Indian Pulsar Timing Array (InPTA) collaboration has recently made its first official data release (DR1) for a sample of 14 pulsars using 3.5 years uGMRT observations. We present the results single-pulsar noise analysis each these InPTA DR1. For this purpose, we consider white noise, achromatic red dispersion measure (DM) variations, and scattering variations in our analysis. apply Bayesian model selection to obtain preferred models among pulsar. PSR J1600$-$3053, find no evidence DM...
ABSTRACT The wideband timing technique enables the high-precision simultaneous estimation of pulsar times arrival (ToAs) and dispersion measures (DMs) while effectively modelling frequency-dependent profile evolution. We present two novel independent methods that extend standard to handle multiband data incorporating evolution over a larger frequency span estimate DMs ToAs with enhanced precision. implement likelihood using libstempo python interface perform in tempo2 framework. application...
ABSTRACT We present four new fast radio bursts discovered in a search of the Parkes 70-cm pulsar survey data archive for dispersed single pulses and bursts. searched dispersion measures (DMs) ranging between 0 5000 pc cm−3 with HEIMDALL FETCH detection classification algorithms. All (FRBs) have significantly larger widths (>50 ms) than almost all FRBs detected catalogued to date. The large pulse are not dominated by interstellar scattering or dispersive smearing within channels. One...
Abstract High-precision pulsar timing observations are limited in their accuracy by the jitter noise that appears arrival time of pulses. Therefore, it is important to systematically characterise amplitude and its variation with frequency. In this paper, we provide measurements from low-frequency wideband PSR J0437 $-$ 4715 using data obtained as part Indian Pulsar Timing Array experiment. We were able detect both 300–500 MHz 1 260–1 460 upgraded Giant Metrewave Radio Telescope (uGMRT). The...
ABSTRACT A pulsar’s pulse profile gets broadened at low frequencies due to dispersion along the line of sight or multipath propagation. The dynamic nature interstellar medium makes both these effects time-dependent and introduces slowly varying time delays in measured times-of-arrival similar those introduced by passing gravitational waves. In this article, we present an improved method correct for such obtaining unbiased measure (DM) measurements using low-frequency estimates scattering...
The Indian Pulsar Timing Array (InPTA) collaboration has recently made its first official data release (DR1) for a sample of 14 pulsars using 3.5 years uGMRT observations. We present the results single-pulsar noise analysis each these InPTA DR1. For this purpose, we consider white noise, achromatic red dispersion measure (DM) variations, and scattering variations in our analysis. apply Bayesian model selection to obtain preferred models among pulsar. PSR J1600$-$3053, find no evidence DM...
Milli-second pulsars with highly stable periods can be considered as very precise clocks and used for pulsar timing array (PTA) which attempts to detect nanoheltz gravitational waves (GWs) directly. Main sources of GWs are supermassive black hole (SMBH) binaries have sub-pc-scale orbits. On the other hand, a SMBH binary is in an earlier phase has pc-scale orbit emits ultra-low-frequency ($\lesssim 10^{-9}\,\mathrm{Hz}$) cannot detected conventional methodology PTA. Such tend obtain high...
We present the pulse arrival times and high-precision dispersion measure estimates for 14 millisecond pulsars observed simultaneously in 300-500 MHz 1260-1460 frequency bands using upgraded Giant Metrewave Radio Telescope (uGMRT). The data spans over a baseline of 3.5 years (2018-2021), is first official release made available by Indian Pulsar Timing Array collaboration. This presents unique opportunity investigating interstellar medium effects at low radio frequencies their impact on timing...
Decades long monitoring of millisecond pulsars, which exhibit highly stable rotational periods, in pulsar timing array experiments is on the threshold discovering nanohertz stochastic gravitational wave background. This paper describes Indian Pulsar (InPTA) experiment, employs upgraded Giant Metrewave Radio Telescope (uGMRT) for an ensemble pulsars this purpose. We highlight InPTA's observation strategies and analysis methods, are relevant a future PTA experiment with more sensitive Square...
The wideband timing technique enables the high-precision simultaneous estimation of pulsar Times Arrival (ToAs) and Dispersion Measures (DMs) while effectively modeling frequency-dependent profile evolution. We present two novel independent methods that extend standard to handle multi-band data incorporating evolution over a larger frequency span estimate DMs ToAs with enhanced precision. implement likelihood using libstempo python interface perform in tempo2 framework. application these...
A pulsar's pulse profile gets broadened at low frequencies due to dispersion along the line of sight or multi-path propagation. The dynamic nature interstellar medium makes both these effects time-dependent and introduces slowly varying time delays in measured times-of-arrival similar those introduced by passing gravitational waves. In this article, we present a new method correct for such obtaining unbiased measure (DM) measurements using low-frequency estimates scattering parameters. We...
High-precision pulsar timing observations are limited in their accuracy by the jitter noise that appears arrival time of pulses. Therefore, it is important to systematically characterise amplitude and its variation with frequency. In this paper, we provide measurements from low-frequency wideband PSR J0437$-$4715 using data obtained as part Indian Pulsar Timing Array experiment. We were able detect both 300 - 500 MHz 1260 1460 upgraded Giant Metrewave Radio Telescope (uGMRT). The former...