Yashwant Gupta
Articles written in Journal of Astrophysics and Astronomy
Volume 37 Issue 4 December 2016 Article ID 0036 Review
Neutron Star Physics in the Square Kilometre Array Era: An Indian Perspective
Sushan Konar Manjari Bagchi Debades Bandyopadhyay Sarmistha Banik Dipankar Bhattacharya Sudip Bhattacharyya R. T. Gangadhara A. Gopakumar Yashwant Gupta B. C. Joshi Yogesh Maan Chandreyee Maitra Dipanjan Mukherjee Archana Pai Biswajit Paul Alak K. Ray Firoza K. Sutaria
It is an exceptionally opportune time for astrophysics when a number of next-generation mega-instruments are poised to observe the Universe across the entire electromagnetic spectrum with unprecedented data quality. The Square Kilometre Array (SKA) is undoubtedly one of the major components of this scenario. In particular, the SKA is expected to discover tens of thousands of new neutron stars giving a major fillip to a wide range of scientific investigations. India has a sizeable community of scientists working on different aspects of neutron star physics with immediate access to both the uGMRT (an SKA pathfinder) and the recently launched X-ray observatory Astrosat. The current interests of the community largely centre around studies of (a) the generation of neutron stars and the SNe connection, (b) the neutron star population and evolutionary pathways, (c) the evolution of neutron stars in binaries and the magnetic fields, (d) the neutron star equation of state, (e) the radio pulsar emission mechanism, and (f) the radio pulsars as probes of gravitational physics. Most of these studies are the main goals of the SKA first phase, which is likely to be operational in the next four years. This article summarizes the science goals of the Indian neutron star community in the SKA era, with significant focus on coordinated efforts among the SKA and other existing/upcoming instruments.
Volume 37 Issue 4 December 2016 Article ID 0037 Review
Fast Transients with the Square Kilometre Array and its Pathfinders: An Indian Perspective
Yashwant Gupta Poonam Chandra Manjari Bagchi Niruj M. Ramanujam Yogesh Maan Avinash A. Deshpande Siddhartha Bhattacharyya
In the rapidly developing field of study of the transient sky,fast radio transients are perhaps the most exciting objects of scrutiny at present. The SKA, with its wide field-of-view and significant improvement in sensitivity over existing facilities, is expected to detect a plethora of fast transients which, in addition to help resolve the mysteries surrounding their nature and origin, will also lead to other interesting applications in astrophysics. We explore some of these possibilities here, and also emphasize the current status and future plans of the Indian communityworking in this area, in the context of ongoing work and extensionof this to the SKA.
Volume 37 Issue 4 December 2016 Article ID 0040 Editorial
Tirthankar Roy Choudhury Yashwant Gupta
Volume 43 All articles Published: 22 September 2022 Article ID 0068 OBSERVATIONAL FACILITIES
The Square Kilometre Array: current status and India’s role in this upcoming facility
The Square Kilometre Array (SKA) observatory is a next-generation radio astronomy facility, which is just started its construction, after successful completion of the design and early prototyping phases. With more than 12 countries currently participating in the international consortium to build this facility, the SKA is expected to revolutionize radio astronomy, while driving the growth of many important new state of the art technologies. Once completed and fully operational by the turn of this decade, the SKA observatory will offer cutting edge science capabilities in an extremely broad range of topics in astrophysics. Indian scientists and engineers have played a significant role in the definition of the SKA concept and its science case as well as in the design of the instrument. India is now getting ready to join the construction phase of the SKA, and Indian astronomers are preparing to engage in front line science with the facility as and when it is ready. This paper describes the current status of this global project with a focus on India’s role in the collaboration.
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 All articles Published: 25 March 2023 Article ID 0021 TECHNICAL REVIEW
YASHWANT GUPTA VIVEK MOHILE JITENDRA KODILKAR RAJ UPRADE YOGESH WADADEKAR SUBHROJYOTI ROY CHAUDHURI
India has been a significant contributor to the SKA project from 2009, with a special emphasis on the Telescope Manager, the central control system for the SKA Observatory. This paper describes the details of the design and early prototyping phases of the Telescope Manager work package, including the accompanying life cycle activities. It also traces the history of India’s involvement in the work on the Telescope Manager in various phases of the project, describing the contribution starting with the concept design to the currentlyongoing construction phase, and looks at the road ahead. The details of the design and the outcomes of the prototyping and development contributed by India in each phase, are also included.
Volume 44 All articles Published: 31 March 2023 Article ID 0027 OVERVIEW
India and the SKA: An overview
YASHWANT GUPTA D. BHATTACHARYA T. ROY CHOUDHURY Y. WADADEKAR T. PRABU
The Square Kilometre Array (SKA) Observatory is a next-generation radio astronomy facility that has recently entered into the construction phase, after successful completion of the design and prototyping phases during 2013–2021. Planned to be operational by the end of this decade, the SKA is expected to revolutionise astronomy by allowing cutting edge explorations in an extremely wide range of science areas, while driving the growth of many important new state-of-the-art technologies. There are more than 10 countries currentlyparticipating in the international consortium to build this facility, which will be co-located in Australia andSouth Africa with the global headquarters in the United Kingdom. Indian scientists and engineers have played a significant role since the beginning: from the definition of the SKA concept and its science case, to some important aspects of the design of the instrument and the prototyping activities. India is now getting ready to join the construction phase of the SKA with a well defined proposal for technical activities spanning a few different areas of work. Along with this, Indian astronomers are busy refining their science case for the SKA and preparing in different ways to be ready for front line science with the facility as and when it is commissioned. All these activities are coordinated by the SKA India consortium, which currently has a membership of more than 20 institutions across the country. In this paper, we describe the current status of the SKA project, and focus on India’s role—past contributions, ongoing activities and future plans.
Volume 44 All articles Published: 31 March 2023 Article ID 0028 TECHNICAL REVIEW
Progression of digital-receiver architecture: From MWA to SKA1-Low, and beyond
B. S. GIRISH S. HARSHAVARDHAN REDDY SHIV SETHI K. S. SRIVANI R. ABHISHEK B. AJITHKUMAR SAHANA BHATTRAMAKKI KAUSHAL BUCH SANDEEP CHAUDHURI YASHWANT GUPTA P. A. KAMINI SANJAY KUDALE S. MADHAVI MEKHALA MULEY T. PRABU AGARAM RAGHUNATHAN G. J. SHELTON
Backed by advances in digital electronics, signal processing, computation and storage technologies, aperture arrays, which had strongly influenced the design of telescopes in the early years of radio astronomy, havemade a comeback. Amid all these developments, an international effort to design and build the world’s largest radio telescope, the Square Kilometre Array (SKA), is ongoing. With its vast collecting area of 1 km$^2$, the SKA is envisaged to provide unsurpassed sensitivity and leverage technological advances to implement a complex receiver to provide a large field of view through multiple beams on the sky. Many pathfinders and precursor aperture array telescopes for the SKA, operating in the frequency range of 10–300 MHz, have been constructed and operationalized to obtain valuable feedback on scientific, instrumental and functional aspects. This review article looks explicitly into the progression of digital-receiver architecture from the Murchison Widefield Array(precursor) to the SKA1-Low. It highlights the technological advances in analog-to-digital converters (ADCs), field-programmable gate arrays (FPGAs) and central processing unit–graphics processing unit (CPU–GPU) hybrid platforms around which complex digital signal processing systems implement efficient channelizers, beamformers and correlators. The article concludes with a preview of the design of a new generation signal processing platform based on radio frequency system-on-chip (RFSoC).
Volume 44, 2023
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