M. A. Krishnakumar
Reader-F
Email: kkma [at] ncra.tifr.res.in
Phone: 0423 - 2244942
Extn: 0423 - 2244942
Office: RAC316
Radio Astronomy Centre
Tata Institute of Fundamental Research
Udhagamandalam - 643001,
Tamil Nadu, INDIA
Tata Institute of Fundamental Research
Udhagamandalam - 643001,
Tamil Nadu, INDIA
Main Research Areas: Pulsars, Ionised and Magnetised Interstellar medium, Data Analysis and Software development; Pulsar Timing Arrays
Biography:
Krishnakumar obtained his B.Sc. from S.N College Shoranur, Calicut University, in 2009 and his M.Sc. from Amrita Vishwa Vidyapeetham University, Coimbatore, in 2011. He then joined the Radio Astronomy Centre, Ooty, as a project junior research fellow in 2012. He obtained his Ph.D. from Bharathiar University, Coimbatore, in 2020 with the doctoral research carried out at the Radio Astronomy Centre, Ooty, on studying the ionised interstellar medium using pulsars as probes using very low and high frequency radio observations as well as other techniques. After two post-doctoral positions at the radio astronomy group of Bielefeld University, Germany (2018-2021) and Max Planck Institute for Radio Astronomy, Bonn, Germany (2021-2024), he joined the National Centre for Radio Astrophysics as a faculty member in March 2024.Research description:
My broad research interest is to understand the ionised and magnetised interstellar medium as well as the heliosphere using different probes like pulsars and other compact radio sources. My current research work focuses on (1) Scattering and scintillation of pulsar signals, (2) Noise characterisation in the pulsar timing array data sets, (3) Developing new data analysis tools and simulation packages.
Scattering and scintillation of pulsars
Scattering of radio waves as it propagates through the ionised interstellar medium (IISM) helps in studying the characteristics of the turbulence as well as help in studying structures in the IISM. The major observables with pulsars are pulse broadening and scintillation of pulse intensity over frequencies. Some of my earlier large scale radio observations helped in understanding the IISM turbulence scales. Moreover, interesting features of the scattering screens can be derived from the secondary spectra of scintillation. My current interest in this is to understand the long-term variation in some of these observables and to understand the properties of the IISM.
Scattering of radio waves as it propagates through the ionised interstellar medium (IISM) helps in studying the characteristics of the turbulence as well as help in studying structures in the IISM. The major observables with pulsars are pulse broadening and scintillation of pulse intensity over frequencies. Some of my earlier large scale radio observations helped in understanding the IISM turbulence scales. Moreover, interesting features of the scattering screens can be derived from the secondary spectra of scintillation. My current interest in this is to understand the long-term variation in some of these observables and to understand the properties of the IISM.
Noise characterisation of the PTA data sets
Pulsar Timing Arrays search for low frequency Gravitational Waves using high precision time of arrivals (ToAs) of pulsars. These ToAs are affected by different chromatic propagation delays like dispersion and scattering as well as achromatic noise due to pulsar spin noise. The PTAs recently found evidence for a gravitational wave background signal. To improve the evidence, one need to model these noise properties precisely. In addition to the above mentioned IISM delays, an annual variation on ToAs (and consecutively on dispersion) is detected on several low ecliptic latitude pulsars due to their approach to the Sun.
Pulsar Timing Arrays search for low frequency Gravitational Waves using high precision time of arrivals (ToAs) of pulsars. These ToAs are affected by different chromatic propagation delays like dispersion and scattering as well as achromatic noise due to pulsar spin noise. The PTAs recently found evidence for a gravitational wave background signal. To improve the evidence, one need to model these noise properties precisely. In addition to the above mentioned IISM delays, an annual variation on ToAs (and consecutively on dispersion) is detected on several low ecliptic latitude pulsars due to their approach to the Sun.
Developing new data analysis tools and simulation packages
Development of new data analysis techniques and simulation tools are a must in the current era of data-intense astronomy. I was heavily involved in the development of the pulsar data analysis package we developed for the LOFAR4SW project. I have developed a new simulation package recently for creating observation quality pulsar data sets for understanding the various parameters that can be recovered by the different data analysis packages.
Development of new data analysis techniques and simulation tools are a must in the current era of data-intense astronomy. I was heavily involved in the development of the pulsar data analysis package we developed for the LOFAR4SW project. I have developed a new simulation package recently for creating observation quality pulsar data sets for understanding the various parameters that can be recovered by the different data analysis packages.
Selected publications:
1. Exploring the time variability of the solar wind using LOFAR pulsar data (S. C. Susarla et al. 2024, A&A, 692A, 18) 2. Periodic interstellar scintillation variations of PSRs J0613–0200 and J0636+5128 associated with the Local Bubble shell (Y. Liu et al., 2023, SCPMA, 6619512) 3. Pulsar scintillation studies with LOFAR: II. Dual-frequency scattering study of PSR J0826+2637 with LOFAR and NenuFAR (Z. Wu et al. 2023, MNRAS, 520, 5536) 4. The Indian Pulsar Timing Array: First data release (P. Tarafdar et al. 2022, PASA, 39, 53) 5. High precision measurements of interstellar dispersion measure with the upgraded GMRT (M. A. Krishnakumar et al. 2021, A&A, 651A, 5) 6. A real-time automated glitch detection pipeline at Ooty Radio Telescope (J. Singha, A. Basu, M. A. Krishnakumar et al., 2021, MNRAS, 505, 5488) 7. Multi-frequency Scatter-broadening Evolution of Pulsars. II. Scatter-broadening of Nearby Pulsars (M. A. Krishnakumar et al. 2019, ApJ, 878, 130) 8. Scatter Broadening Measurements of 124 Pulsars At 327 Mhz (M. A. Krishnakumar et al. 2015, ApJ, 804, 23)
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