• Siddhartha Bhattacharyya

      Articles written in Journal of Astrophysics and Astronomy

    • 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

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      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.

    • FRB Event Rate Predictions for the Ooty Wide Field Array

      Siddhartha Bhattacharyya Apurba Bera Somnath Bharadwaj N. D. Ramesh Bhat Jayaram N. Chengalur

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      We developed a generic formalism to estimate the event rate and the redshift distribution of Fast Radio Bursts (FRBs) in our previous publication (Bera et al. 2016), considering FRBs are of an extragalactic origin. In this paper, we present (a) the predicted pulse widths of FRBs by considering two different scattering models, (b) the minimum total energy required to detect events, (c) the redshift distribution and (d) the detection rates of FRBs for the Ooty Wide Field Array (OWFA). The energy spectrum of FRBs is modelled as a power law with an exponent $-\alpha$ and our analysis spans a range $-3\leq \alpha \leq 5$. We find that OWFA will be capable of detecting FRBs with $\alpha\geq 0$. The redshift distribution and the event rates of FRBs are estimated by assuming two different energy distribution functions; a Delta function and a Schechter luminosity function with an exponent $-2\le \gamma \le 2$. We consider an empirical scattering model based on pulsar observations (model I) as well as a theoretical model (model II) expected for the intergalactic medium. The redshift distributions peak at a particular redshift $z_p$ for a fixed value of α, which lie in the range $0.3\leq z_p \leq 1$ for the scattering model I and remain flat and extend up to high redshifts ($z\lesssim 5$) for the scattering model II.

    • Prospects of detecting fast radio bursts using Indian radio telescopes


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      Fast Radio Bursts (FRBs) are short duration highly energetic dispersed radio pulses.We developed a generic formalism (Bera et al. 2016, MNRAS, 457, 2530) to estimate the FRB detection rate for any radiotelescope with given parameters. By using this model, we estimated the FRB detection rate for two Indian radio telescope; the Ooty Wide Field Array (OWFA) (Bhattacharyya et al. 2017, J. Astrophys. Astr., 38, 17)and the upgraded Giant Metrewave Radio Telescope (uGMRT) (Bhattacharyya et al. 2018, J. Astrophys. Astr.) with three beam-forming modes. Here, we summarize these two works.We considered the energy spectrum ofFRBs as a power law and the energy distribution of FRBs as a Dirac delta function and a Schechter luminosity function.We also considered two scattering models proposed by Bhat et al. (2004, Astrophys. J. Suppl. Series,206, 1) and Macquart & Koay (2013, ApJ, 776, 125) for these works and we consider FRB pulse without scattering as a special case. We found that the future prospects of detecting FRBs by using these two Indian radio telescopes is good. They are capable to detect a significant number of FRBs per day. According to our prediction, we can detect $\sim$10$^5$−10$^8$, $\sim$10$^3$−10$^6$ and $\sim$10$^5$−10$^7$ FRBs per day by using OWFA, commensal systems of GMRT and uGMRT respectively. Even a non detection of the predicted events will be very useful in constraining FRB properties.

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    • 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.

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