DHRUV PATHAK
Articles written in Journal of Astrophysics and Astronomy
Volume 39 Issue 4 August 2018 Article ID 0051 Review
Precision pulsar timing with the ORT and the GMRT and its applications in pulsar astrophysics
BHAL CHANDRA JOSHI PRAKASH ARUMUGASAMY MANJARI BAGCHI DEBADES BANDYOPADHYAY AVISHEK BASU NEELAM DHANDA BATRA SURYARAO BETHAPUDI ARPITA CHOUDHARY KISHALAY DE L. DEY A. GOPAKUMAR Y. GUPTA M. A. KRISHNAKUMAR YOGESH MAAN P. K. MANOHARAN ARUN NAIDU RANA NANDI DHRUV PATHAK MAYURESH SURNIS ABHIMANYU SUSOBHANAN
Radio pulsars show remarkable clock-like stability, which make them useful astronomy tools in experiments to test equation of state of neutron stars and detecting gravitational waves using pulsar timing techniques. A brief review of relevant astrophysical experiments is provided in this paper highlighting thecurrent state-of-the-art of these experiments. A program to monitor frequently glitching pulsars with Indian radio telescopes using high cadence observations is presented, with illustrations of glitches detected in this program, including the largest ever glitch in PSR B0531 $+$ 21. An Indian initiative to discover sub-$\mu$Hz gravitational waves, called Indian Pulsar Timing Array (InPTA), is also described briefly, where time-of-arrival uncertainties and post-fit residuals of the order of $\mu$s are already achievable, comparable to other international pulsar timing array experiments. While timing the glitches and their recoveries are likely to provide constraints on the structure of neutron stars, InPTA will provide upper limits on sub-$\mu$Hz gravitational waves apart from auxiliary pulsarscience. Future directions for these experiments are outlined.
Volume 43 All articles Published: 8 December 2022 Article ID 0098 SCIENTIFIC REVIEW
Nanohertz gravitational wave astronomy during SKA era: An InPTA perspective
BHAL CHANDRA JOSHI ACHAMVEEDU GOPAKUMAR ARUL PANDIAN THIAGARAJ PRABU LANKESWAR DEY MANJARI BAGCHI SHANTANU DESAI PRATIK TARAFDAR PRERNA RANA YOGESH MAAN NEELAM DHANDA BATRA RAGHAV GIRGAONKAR NIKITA AGARWAL PARAMASIVAN ARUMUGAM AVISHEK BASU ADARSH BATHULA SUBHAJIT DANDAPAT YASHWANT GUPTA SHINNOSUKE HISANO RYO KATO DIVYANSH KHARBANDA TOMONOSUKE KIKUNAGA NEEL KOLHE M. A. KRISHNAKUMAR P. K. MANOHARAN PIYUSH MARMAT ARUN NAIDU SARMISTHA BANIK K. NOBLESON AVINASH KUMAR PALADI DHRUV PATHAK JAIKHOMBA SINGHA AMAN SRIVASTAVA MAYURESH SURNIS SAI CHAITANYA SUSARLA ABHIMANYU SUSOBHANAN1 KEITARO TAKAHASHI
Decades long monitoring of millisecond pulsars, which exhibit highly stable rotational periods in pulsar timing array experiments is on the threshold of discovering nanohertz stochastic gravitational wave background. This paper describes the Indian pulsar timing array (InPTA) experiment, which employs the upgraded Giant Metrewave Radio Telescope (uGMRT) for timing an ensemble of millisecond pulsars for thispurpose. We highlight InPTA’s observation strategies and analysis methods, which are relevant for a future PTA experiment with the more sensitive Square Kilometer Array (SKA) telescope. We show that the unique multi-sub-array multi-band wide-bandwidth frequency coverage of the InPTA, provides dispersion measureestimates with unprecedented precision for PTA pulsars, e.g., $\sim$$2 \times 10^{−5}$ pc cm$^{−3}$ for PSR J1909-3744. Configuring the SKA-low and SKA-mid as two and four sub-arrays, respectively, it is shown that comparable precision is achievable, using observation strategies similar to those pursued by the InPTA, for a larger sample of 62 pulsars, requiring about 26 and 7 h per epoch for the SKA-mid and the SKA-low telescopes, respectively. We also review the ongoing efforts to develop PTA-relevant general relativistic constructs that will be required to search for nanohertz gravitational waves from isolated super-massive black hole binary systems like blazar OJ 287. These efforts should be relevant to pursue persistent multi-messenger gravitational wave astronomy during the forthcoming era of the SKA telescope, the thirty meter telescope, and the next-generation eventhorizon telescope.
Volume 44, 2023
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