Yashwant Gupta

Centre Director, NCRA-TIFR
Email: ygupta [at] ncra.tifr.res.in
Phone: +91 - 20 - 25719242
Extn: 9242
Office: 201
National Centre for Radio Astrophysics
Tata Institute of Fundamental Research
Savitribai Phule Pune University Campus,
Pune 411 007
Maharashtra, INDIA


Main Research Areas: Pulsar searches, timing studies, and emission mechanisms; The Interstellar Medium; Radio Astronomy Instrumentation.

Biography:

Yashwant Gupta obtained his M.S. and Ph.D. in Radio Astronomy from the University of California, San Diego in 1990, after completing his Bachelor's degree in Electrical Engineering from IIT-Kanpur in 1985. Since 1991, he has been working at the National Centre for Radio Astrophysics (NCRA-TIFR, Pune) of the Tata Institute of Fundamental Research, where he currently holds the position of Senior Professor. In March 2005, he was appointed to the position of Chief Scientist at the Giant Metrewave Radio Telescope (GMRT) -- a world-class instrument built and operated by NCRA-TIFR and located about 80 km from Pune. Since 2010, he holds the position of Dean, GMRT Observatory.

Research description:

My research areas cover different aspects of the study of pulsars -- rapidly rotating compact neutron stars that emit intense beams of radio emission. Areas of interest range from detailed studies of their emission process, searching for and finding new pulsars, timing studies to understand their dynamics, and using them as a probe to study the interstellar medium. The other main area of interest is development of new instrumentation and signal processing techniques for radio astronomy.
Searching for pulsars:
Though more than 2000 pulsars have been found by astronomers so far, there are many more waiting to be discovered, including some that could be much more interesting and exotic than the ones found so far. In addition to blind searches that target large areas of the sky in a uniform manner using sensitive telescopes like the GMRT, I have been involved in targeted searches in specific locations such as supernova remnants, globular clusters and compact sources of high energy emission that are likely to harbour neutron stars. Some very unique and interesting pulsars have been discovered in these searches and I continue to be involved in further explorations of this kind.
Timing studies of pulsars:
Once a new pulsar is discovered, a host of interesting new things can be learnt about it (and its environment) by a careful study of the time of arrival of the pulses, over long durations of time, spanning weeks to months to years. I continue to be involved in several such studies that have (a) revealed irregularities in rotation (called glitches) in young neutron stars, and (b) been used to infer the nature of the orbit for neutron stars in binary systems, in addition to determining basic parameters like accurate values for the period and its derivative with time. Another interesting area of my research is the study of timing noise -- the residual random behaviour seen in timing data when all known effects have been modelled.
Understanding radio emission properties:
Working out exactly how and why radio pulsars shine remains one of the biggest unsolved problems in the field. Some of my research work revolves around efforts to try and understand better the location and distribution of emission regions in the magnetosphere of a neutron star, aided and abetted by high quality single frequency and simultaneous multi-frequency observations of phenomena such as drifting subpulses, using the GMRT. Even as we improve our understanding of such issues, there is much to learn and look forward to in this exciting area of work.
Probing the interstellar medium using pulsars:
Due to the fact that pulsars are extremely compact objects and emit narrow duty pulses, they form excellent probes of several properties of the interstellar medium (ISM). My interest here ranges from a more detailed understanding of the distribution of the ionised plasma of the ISM, to using interstellar scintillations as a probe to resolve the very compact emission regions of pulsars.
Instrumentation for radio astronomy:
The development of next generation instrumentation for radio telescopes is an area of keen interest for me. In particular, my emphasis is on digital back-end systems which can play an important role in expanding the capabilities and versatility of a radio telescope, enabling new science to be carried out. I have been actively involved in 3 generations of back-ends for the GMRT, starting with a completely hardware-based implementation to a software-based approach using general purpose CPUs, and now to using accelerated computing with GPUs for the back-end for the upgraded GMRT.

Selected publications:

1.  GMRT Discovery of PSR J1544+4937: An Eclipsing Black-widow Pulsar Identified with a Fermi-LAT Source (B. Bhattacharyya, J. Roy, P. S. Ray, Y. Gupta et al. 2013, ApJL, 773, L12)

2.   The GMRT-EoR Experiment : A new upper limit on the neutral hydrogen power spectrum at z ≈ 8.6 (G. Paciga, T-C. Chang, Y. Gupta, Y. et al. 2011, MNRAS, 413, 1174)

3. A real-time software backend for the GMRT  (J. Roy, Y. Gupta et al. 2010, Experimental Astronomy, 28, 25)

4. Discovery of a remarkable subpulse drift pattern in PSR B0818-41 (B. Bhattacharyya, Y. Gupta, J. Gil & M. Sendyk 2007, MNRAS, 377, L10)

5. Discovery of PSRJ1833-1034 : the pulsar associated with the supernova remnant G21.5-0.9 (Y. Gupta et al. 2005, 89, 853)

6. Giant Metrewave Radio Telescope Discovery of a Millisecond Pulsar in a Very Eccentric Binary System (P. Freire, Y. Gupta, S. M. Ransom & C. H. Ishwara-Chandra 2004, ApJL, 606, L53)

7. Unraveling the drift behaviour of the remarkable pulsar PSR B0826-34 (Y. Gupta et al. 2004, A&A, 426, 229)

8. Understanding the Radio Emission Geometry of Multiple-Component Radio Pulsars from Retardation and Aberration Effects  (Y. Gupta & R. T. Gangadhara 2003, ApJ, 584, 418)

9. Multiple Imaging of PSR B1133+16 by the Interstellar Medium (Y. Gupta et al. 1999, ApJ, 520, 173)

10. Pulsar Scintillation and the Local Bubble (R. Bhat N.D., Y.Gupta & A. P. Rao 1998, ApJ, 500, 262)

11. On the Correlation between Proper Motion Velocities and Scintillation Velocities of Radio Pulsars (Y.Gupta 1995, ApJ, 451, 717)

12. Refractive Interstellar Scintillation in Pulsar Dynamic Spectra  (Y.Gupta et al. 1994, MNRAS, 269, 1035)

13. Refractive interstellar scintillation of pulsar intensities at 74 MHz (Y.Gupta et al. 1993, ApJ, 403, 183)




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