A5077515499- Pulsars and Gravitational Waves Research
- Radio Astronomy Observations and Technology
- GNSS positioning and interference
- Advanced Frequency and Time Standards
- Geophysics and Gravity Measurements
- Galaxies: Formation, Evolution, Phenomena
- Astrophysics and Cosmic Phenomena
- Astrophysical Phenomena and Observations
- Astronomy and Astrophysical Research
- Astrophysics and Star Formation Studies
- Gamma-ray bursts and supernovae
- Advanced Mathematical Theories
- Musicology and Musical Analysis
- Relativity and Gravitational Theory
- Seismic Waves and Analysis
- Superconducting and THz Device Technology
- Seismic Imaging and Inversion Techniques
- Cosmology and Gravitation Theories
- Stellar, planetary, and galactic studies
- Image and Signal Denoising Methods
University of Delhi
2022-2024
Indian Institute of Technology Delhi
2018-2022
Birla Institute of Technology and Science - Hyderabad Campus
2018-2021
Campbell Collaboration
2019
Malaviya National Institute of Technology Jaipur
2014
Michigan State University
2007-2014
Kitt Peak National Observatory
2007
Association of Universities For Research In Astronomy
2007
U.S. National Science Foundation
2007
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...
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...
We measured the metallicity Z in broad emission-line regions (BELRs) of 43 Sloan Digital Sky Survey (SDSS) quasars with strongest N iv] and iii] emission lines. These N-loud quasi-stellar objects (QSOs) have unusually low-black-hole masses. used intensity ratio lines to collisionally excited other heavy elements find metallicities their BELR regions. found that seven eight line-intensity ratios we employed give roughly consistent as measured, but for each individual QSO differences from mean...
Abstract We introduce pinta , a pipeline for reducing the upgraded Giant Metre-wave Radio Telescope (uGMRT) raw pulsar timing data, developed Indian Pulsar Timing Array experiment. provide detailed description of workflow and usage as well its computational performance RFI mitigation characteristics. also discuss novel independent determination relative time offsets between different back-end modes uGMRT interpretation observation frequency settings their agreement with results obtained from...
Pulsar radio emission undergoes dispersion due to the presence of free electrons in interstellar medium (ISM). The dispersive delay arrival time pulsar signal changes over varying ISM electron column density along line sight. Correcting for this accurately is crucial detection nanohertz gravitational waves using Timing Arrays. In work, we present in-band and inter-band DM estimates four pulsars observed with uGMRT timescale a year two different template alignment methods. DMs obtained both...
We study the degree of chemical enrichment in Broad Emission Line Regions (BELRs) two QSOs with unusually strong nitrogen emission lines. The N V 1240/ C IV 1549 intensity ratio is often used as a metallicity indicator for QSOs. validity this approach can be tested by studying objects which IV] and III] lines, addition to V, are easily measurable. If all these ionization states point same metallicity, it implies that large strengths observed most not due some peculiarity 1240 line. This test...
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...
We consider a neutrino-free hot neutron star that contains antikaon condensates in its core and is at finite entropy per baryon. find the equation of state for range entropies optical potentials generate mass profile static as well rotating stars. Rotation induces many changes stellar equilibrium, hence structural properties evolve. In this work, we report effect rotation on shape different equations thermodynamic conditions. Temperature hot, also explored. make crude estimate amplitude...
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 is an experiment aimed at detection of Gravitational waves (GWs) in the sub-microHertz frequency range by observing ensemble millisecond pulsars (MSPs). GWs from both stochastic GW background as well individual sources like supermassive black hole binaries (SMBHBs) leave imprint on time-of-arrival (TOA) pulsed emission MSPs, which could be detected with high precision due to clock-like stability these pulsars. InPTA aims contribute its data and analysis results...
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...
We measured the metallicity Z in broad emission line regions (BELRs) of 43 SDSS quasars with strongest N IV] and III] lines. These N-Loud QSOs have unusually low black hole masses. used intensity ratio lines to collisionally-excited other heavy elements find metallicities their BELR regions. found that 7 8 line-intensity ratios we employed give roughly consistent as measured, but for each individual QSO differences from mean all measurements depends on ionization potential ions form After...
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...