• Sarmistha Banik

Articles written in Journal of Astrophysics and Astronomy

• Neutron Star Physics in the Square Kilometre Array Era: An Indian Perspective

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.

• Quasi-stationary sequences of hyper-massive neutron stars with exotic equations of state

In this work, we study the effect of differential rotation, finite temperature and strangeness on the quasi-stationary sequences of hyper-massive neutron stars. We generate constant rest-mass sequences of differentially rotating and uniformly rotating stars. The nucleonic matter relevant to the star interior is described within the framework of relativistic mean field model with the DD2 parameter set. We alsoconsider the strange $\Lambda$ hyperons using the BHB$\Lambda\phi$ equation of state (EoS). Additionally, we probe the behaviour of neutron stars (NS) with these compositions at different temperatures. We report that the addition of hyperons to the EoS, produces a significant boost to the spin-up phenomenon. Moreover,increasing the temperature can make the spin-up more robust. We also study the impact of strangeness and thermal effects on the T/W instability. Finally, we analyse the equilibrium sequences of a NS following a stable transition from differential rotation to uniform rotation. During this transition, the decrease in frequency relative to angular momentum loss is significantly smaller for EoS containing hyperons, compared tonucleonic EoS.

• Pulsar timing irregularities and neutron star interior in the era of SKA: An Indian outlook

There are two types of timing irregularities seen in pulsars: glitches and timing noise. Both of these phenomena can help us to probe the interior of such exotic objects. This paper presents a brief overview of the observational and theoretical aspects of pulsar timing irregularities and the main results from the investigationsof these phenomena in India. The relevance of such Indian programs for monitoring of young pulsars with the square kilometer array (SKA) is presented, highlighting possible contributions of the Indian neutron star community to the upcoming SKA endeavor.

• Nanohertz gravitational wave astronomy during SKA era: An InPTA perspective

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.

• # Journal of Astrophysics and Astronomy

Volume 44, 2023
All articles
Continuous Article Publishing mode

• # Continuous Article Publication

Posted on January 27, 2016

Since January 2016, the Journal of Astrophysics and Astronomy has moved to Continuous Article Publishing (CAP) mode. This means that each accepted article is being published immediately online with DOI and article citation ID with starting page number 1. Articles are also visible in Web of Science immediately. All these have helped shorten the publication time and have improved the visibility of the articles.

• # Editorial Note on Continuous Article Publication

Posted on July 25, 2019